How well do women understand their menstrual cycles? Insights from 383,085 UK based women

Abstract

Background

Menstrual cycle awareness is a critical yet frequently overlooked component of reproductive health; it shapes an individual’s ability to recognise changes in their cycle, seek timely medical care when needed, and make informed decisions. However, many women of reproductive age lack essential understanding about their cycles, contributing to widespread misconceptions, stigma, and delays in healthcare engagement. This study explores menstrual cycle awareness, the perceptions of cycle regularity, and demographic disparities among UK-based women.

Methods

This was a retrospective, cross-sectional analysis of self-reported menstrual cycle data collected through an online health assessment (OHA) between September 2020 and January 2025 from 383,085 UK-based women aged 18–50 years. Participants reported cycle regularity, cycle length, and period length, alongside demographic and reproductive characteristics.

Results

Overall, 22.2% of participants reported not knowing their cycle length, with uncertainty highest among those under 25 years (33.4%). Awareness increased with age before declining slightly after age 45. Awareness of period length was higher than cycle length awareness; however, 9.5% of participants were unable to report period length, rising to 13.8% among those under 25. Among participants who described their cycles as regular and reported a cycle length, 4.9% reported cycle lengths outside commonly referenced regular range (21–35 days), indicating discordance between perceived regularity and reported cycle length. This discordance was most pronounced among younger participants and varied modestly across ethnic groups. Participants who had previously been pregnant or were actively trying to conceive demonstrated higher cycle length awareness.

Conclusions

These findings highlight persistent gaps in menstrual cycle awareness among UK-based women, particularly among younger individuals and those not actively engaged in fertility planning. Discordance between perceived cycle regularity and cycle length reference ranges suggests that many individuals may lack a clear framework for interpreting their menstrual patterns. Improving population-level education and clinical engagement around menstrual cycle awareness beyond fertility-focused contexts may support earlier recognition of potential menstrual health concerns and more timely healthcare engagement.

Background

Menstrual health is increasingly recognised as a public health and gender equity issue, with implications for reproductive health, wellbeing, and healthcare engagement across the life course [1, 2]. The menstrual cycle has been proposed as an additional indicator of overall health, sometimes described as a fifth vital sign [3, 4]. Despite this, data from the UK women’s health strategy survey (WHSS) indicate that fewer than one in five women feel like they have enough information on menstrual wellbeing. Similarly a survey conducted by Endometriosis UK found that the majority of young people (57%) rated their knowledge of the menstrual cycle as poor, with only 15% rating it as strong, and 45% reporting that they did not receive information or support from school or college [5].

Menstrual cycles are characterised by substantial biological variability. Although a 28-day cycle is often cited as average [6], large-scale cycle tracking data from over 600,000 cycles demonstrate wide intra- and inter-individual variation, with only 13% of cycles lasting 28 days [7]. In a study of 32,595 UK- and US-based women, 25.3% selected a 28-day cycle as their perceived cycle length, however, only 12.4% of users actually had a 28-day cycle [8]. Similar findings were reported by Johnson et al. (2018) where 34% of women believed their cycle was 28 days, but only 15% had a 28-day cycle [9]. While some mismatch is expected given natural variability, larger discrepancies may reflect limited cycle awareness.

Interpreting menstrual experiences, however, is not straightforward and distinguishing between normal variation and symptoms that may warrant medical assessment can be challenging, particularly in the absence of comprehensive menstrual health knowledge [10].

Evidence suggests that limited awareness of menstrual symptoms may contribute to delayed help-seeking. In a survey of 200 UK-based women aged 18–45 living with polycystic ovary syndrome (PCOS), delays in accessing medical care were frequently driven by failure to recognise symptoms as clinically significant [10]. In this context, menstrual health education may play an important role in recognising changes over time, identifying potential abnormalities, communicating concerns effectively with healthcare providers and supporting individuals to engage more confidently in decisions about their reproductive health [11–13].

Emerging evidence further suggests that menstrual cycle awareness may influence lived menstrual experiences in adulthood. A study of 97,414 UK-based women aged 18–45 who were trying to conceive found that over one third (41%) were unable to accurately identify the fertile window [14]. However, existing research has largely focused on menstrual hygiene management, fertility awareness, or adolescent populations, with comparatively little attention paid to how adult women understand and interpret their own menstrual cycles, or how awareness varies across demographic and reproductive factors [15, 16]. A recent scoping review supports this gap, showing that among 18 studies of menstrual and reproductive health awareness, ovulation or the fertile window was the primary focus in 16 studies (89%), while fewer than half examined knowledge of menstruation (44%) or female reproductive physiology (44%), and only one third addressed broader factors influencing reproductive health (33%) [17]. Together, this highlights a persistent emphasis on fertility-related knowledge over understanding of everyday menstrual cycle characteristics across adulthood.

This study addresses these gaps by examining menstrual cycle self-awareness among UK-based women. The objectives were (1) to assess self-reported menstrual cycle length, period length, and perceived cycle regularity, and (2) to examine how awareness of one’s own menstrual cycle characteristics varies across demographic and reproductive factors, including age, ethnicity, reproductive history, and contraceptive use. By providing population-level insight into menstrual cycle awareness in adulthood, this research aims to inform more targeted approaches to menstrual health education. To our knowledge, this study is the largest cohort of UK based, addressing the gap in knowledge of how women perceive their own menstrual cycle.

Methods

Study design and population

This study was a retrospective, cross-sectional analysis of self-reported menstrual health data collected via an online health assessment (OHA).

Data were collected between September 2020 and January 2025 through a large-scale digital health platform. All individuals who completed the assessment, were aged 18–50 years, resided in the UK, and provided consent for their anonymised data to be used for research purposes were eligible for inclusion. The total analytical sample comprised 383,085 participants; sample characteristics are presented in the results section.

Data collection and measures

The OHA collected self-reported information on demographic characteristics, reproductive health, menstrual cycle characteristics and medical history. Age was calculated from using date of birth and the date of OHA completion. Ethnicity was self-reported and categorised into the following broad groups for analysis: White, Black, Asian, Mixed, and Other (including Middle Eastern, Indigenous/First Nations, and categories not otherwise specified).

In this study, awareness refers to participants’ ability to report characteristics of their own menstrual cycles, rather than objective menstrual health knowledge. Menstrual cycle characteristics were assessed using self-report items. Participants were asked to describe their cycle pattern by selecting one of the following options: “regular,” “irregular,” “I have never had a period,” “I no longer get periods,” or “I don’t get periods on my form of contraception or hormone replacement therapy.” Cycle length and period length were reported by entering a numerical value or selecting “I don’t know.”

Participants also indicated their primary reason for completing the assessment by indicating whether they were “planning for future babies” ; “actively trying to conceive” ; “just curious”; “experiencing symptoms” ; “menopausal” ; “perimenopausal” or “suspect I am perimenopausal”.

Reproductive conditions were self-reported via a checklist of 18 conditions such as PCOS, endometriosis, etc. Participants were categorised as having a reproductive condition if one or more diagnoses were selected.

The OHA is an assessment tool designed to support reproductive health screening. Although it has not been validated as a formal psychometric scale for measuring menstrual health literacy, its content was informed by review of international clinical guidance from multiple professional bodies, including ESHRE, NICE, RCOG, ACOG, and ASRM, etc. and specialist input from leading experts in reproductive medicine. The assessment was iteratively refined through clinical review and pilot testing to ensure clarity, relevance, and applicability across diverse populations.

For the purposes of this study, participants’ responses were interpreted as measures of self-reported awareness of their own menstrual cycle characteristics rather than objective knowledge or clinical accuracy. Given well-established intra- and inter-individual variability in menstrual cycles, analyses therefore focused on describing patterns in perceived cycle length, period length, and regularity, and examining how these varied across demographic and reproductive characteristics.

Statistical analysis

All statistical analyses were conducted using R (Version 2024.04.2 + 764). Descriptive statistics were calculated for continuous variables, while categorical variables were summarised using frequencies and proportions.

Self-reported cycle length was grouped into three categories: <21 days, 21–35 days, and > 35 days. These categories were selected opposed to Munroe et al., which states a cycle length of ≥ 24 to ≤ 38 days is normal [18] as they are consistent with thresholds commonly used in UK clinical practice and reflected in NHS and NICE guidance when assessing menstrual cycle patterns in routine care [19, 20].

Associations between menstrual cycle self-awareness measures (perceived cycle length, period length, and perceived cycle regularity) and demographic characteristics were assessed using chi-square (χ²) tests for categorical variables. For continuous variables, independent t-tests were used where data met assumptions of normality, and Mann-Whitney U tests for continuous data, where appropriate.

Ethical considerations

This study involved the retrospective analysis of anonymised data collected from individuals who completed an online health assessment via Hertility Health Ltd. At the time of participation, all individuals provided informed consent for their health and personal data to be used in anonymised form for research purposes. Consent was obtained electronically through an opt-in process embedded within the health assessment, with clear information provided regarding data usage, privacy, and confidentiality.

All data analysed were fully anonymised prior to access by the research team, and no identifiable information was used at any stage. As the study involved only retrospective, anonymised data, additional ethical review was not required. However, the research protocol for the online health assessment and testing procedure was reviewed and approved by the London - Surrey Research Ethics Committee, which is part of the The National Health Service (NHS) Health Research Authority (HRA) (REC reference: 20/LO/0265).

All procedures were conducted in compliance with the ethical standards of the institutional and/or national research committee and in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Results

Demographics

The analysis included 383,085 UK-based women aged 18–50 years. Participants were distributed across age groups as follows: 23.6% (n = 90,229) were under 25 years, 32.0% (n = 122,419) were aged 26–30, 27.1% (n = 103,812) were aged 31–35, 11.9% (n = 45,428) were aged 36–40, 4.4% (n = 16,878) were aged 41–45 and 1.1% (n = 4,319) were 45 + years (Table 1).

Table 1.

Demographic and menstrual cycle characteristics of study participants. This table presents the distribution of participants by age, ethnicity, menstrual cycle regularity, and cycle length, providing an overview of the study population’s demographic and reproductive health characteristics

Age group	Frequency	Proportion (%)
< 25	90,229	23.6
26–30	122,419	32
31–35	103,812	27.1
36–40	45,428	11.9
41–45	16,878	4.4
45+	4319	1.1

Ethnicity	Frequency	Proportion (%)
Asian	23,875	6.2
Black	14,042	3.7
Mixed	15,377	4
Other	11,178	2.9
White	318,613	83.2

Cycle description	Frequency	Proportion (%)
Regular	232,620	60.7
Irregular	101,597	26.5
Never had a period	752	0.2
No periods on HRT/contraception	33,330	8.7
Not getting periods	14,786	3.9

Cycle length	Frequency	Proportion (%)
I don’t know	74,183	22.2
< 21	13,710	4.1
21–35	225,288	67.4
> 35	21,036	6.3

Overall, 83.2% identified as White, 6.2% as Asian, 3.7% as Black, 4.0% as Mixed ethnicity, and 2.9% as Other ethnicities (Table 1).

Menstrual cycle characteristics

Of the total cohort, 60.7% (n = 232,620) described their menstrual cycles as regular, while 26.5% (n = 101,597) described them as irregular. A further 8.7% (n = 33,330) reported not menstruating due to hormonal contraception or hormone replacement therapy, 3.9% (n = 14,786) reported not getting periods, and 0.2% (n = 752) reported never having experienced a period.

Among participants who reported menstruating (n = 334,217), more than 1 in 5 (22.2%, n = 74,183) indicated that they did not know their cycle length. Of those who did report a cycle length, 67.4% fell within the 21–35 day range, while 4.1% reported cycle lengths shorter than 21 days and 6.3% reported cycle lengths longer than 35 days (Table 1).

Menstrual cycle length awareness

Awareness of cycle length varied significantly by age (χ²=7,829, p < 0.001). Uncertainty was highest among participants under 25 years, where one in three (33.4%) reported not knowing their cycle length. Uncertainty decreased with age to 15.9% among those aged 36–40 years, before increasing slightly again among participants aged 45 years and older (19.4%) (Table 2).

Table 2.

Knowledge of menstrual cycle length among study participants. This table presents the proportion of participants who knew or did not know their menstrual cycle length, categorized by age, ethnicity, pregnancy history, reproductive health conditions, archetype classifications, and contraception use

	Has menstrual cycles (n = 334,217)
	Knew their cycle length		Did not know cycle length
Age	Frequency	Proportion of group	Frequency	Proportion of group
< 25	50,134	66.6%	25,097	33.4%
26–30	83,205	78.3%	23,023	21.7%
31–35	77,057	82.5%	16,364	17.5%
36–40	34,830	84.1%	6608	15.9%
41–45	12,444	83.1%	2522	16.9%
45+	2364	80.6%	569	19.4%
Ethnicity
Asian	17,562	79.6%	4503	20.4%
Black	10,410	79.8%	2630	20.2%
Mixed	10,747	78.4%	2953	21.6%
Other	8172	80.0%	2041	20.0%
White	213,143	77.5%	62,056	22.5%
Previous pregnancy	2411 skipped this question
Yes	96,184	79.2%	25,313	20.8%
No	162,423	77.2%	47,886	22.8%
Reproductive conditions
Yes	211,087	78.8%	56,899	21.2%
No	48,947	73.9%	17,284	26.1%
Archetype	multiple archetypes could be selected
Planning for the future	110,688	78.0%	31,276	22.0%
Perimenopausal	1034	78.2%	289	21.8%
Menopausal	552	75.8%	176	24.2%
Just curious	70,679	75.8%	22,585	24.2%
Experiencing symptoms	52,814	78.3%	14,676	21.7%
Actively trying to conceive	76,669	82.5%	16,247	17.5%
Suspected perimenopause	18,361	80.8%	4376	19.2%
Contraception
Hormonal	29,823	63.7%	17,000	36.3%
Non hormonal	66,193	83.3%	13,311	16.7%
None	164,018	78.9%	43,872	21.1%

Differences in cycle length awareness were observed across ethnic groups (χ²=124, p < 0.001), although absolute differences were small. Across all ethnic groups, approximately one in five participants reported uncertainty regarding their cycle length (Table 2).

Women who had previously been pregnant were marginally more likely to report knowing their cycle length compared with those who had never been pregnant (79.2% vs. 77.2%; χ²=526, p < 0.001). Awareness was highest among participants actively trying to conceive (82.5%) and lowest among menopausal participants (75.8%) (Table 2).

Uncertainty regarding cycle length was significantly less prevalent among those with diagnosed reproductive conditions (21.2% vs. 26.2%) (χ² = 1552, p < 0.001) (Table 2).

Patterns differed by contraception status (χ² = 6,912, p < 0.001). Participants using hormonal contraception reported the highest levels of uncertainty regarding cycle length (36.3%), compared with users of non-hormonal contraception (16.7%) and those not using contraception (21.1%), likely reflecting the absence of an endogenous menstrual cycle rather than lack of understanding.

Period length awareness

Overall, awareness of period length was higher than awareness of cycle length, although 9.5% of participants reported not knowing how long their periods typically lasted.

Uncertainty regarding period length was highest among participants under 25 years (13.8%) and lowest among those aged 31–35 years (7.5%), with a small increase observed among participants aged 45 years and older (8.2%) (Table 3).

Table 3.

Awareness of menstrual period length among study participants. This table presents the proportion of participants who knew or did not know their menstrual period length, categorised by age, ethnicity, pregnancy history, reproductive health conditions, archetype classifications, bleeding patterns, period pain, and contraception use

	Women who had cycles (n = 334,217)
	Knew period length		Don’t know period length
Age	Frequency	Proportion of group	Frequency	Proportion of group
< 25	64,848	86.2%	10,383	13.8%
26–30	97,087	91.4%	9141	8.6%
31–35	86,425	92.5%	6996	7.5%
36–40	38,234	92.3%	3204	7.7%
41–45	13,685	91.4%	1281	8.6%
45+	2692	91.8%	241	8.2%
Ethnicity
Asian	20,165	91.4%	1900	8.6%
Black	12,026	92.2%	1014	7.8%
Mixed	12,534	91.5%	1166	8.5%
Other	9390	91.9%	823	8.1%
White	248,856	90.4%	26,343	9.6%
Previous pregnancy	1909 skipped this question
Yes	109,809	90.4%	11,688	9.6%
No	191,312	91.0%	18,997	9.0%
Reproductive conditions
Yes	146,476	89.6%	16,983	10.4%
No	156,495	91.6%	14,263	8.4%
Archetype
Planning for the future	129,646	91.3%	12,285	8.7%
Perimenopausal	1203	90.9%	120	9.1%
Menopausal	665	91.5%	62	8.5%
Just curious	84,356	90.5%	8879	9.5%
Experiencing symptoms	61,996	91.9%	5476	8.1%
Actively trying to conceive	85,636	92.2%	7273	7.8%
Suspected perimenopause	20,948	92.1%	1786	7.9%
Bleeding description
heavy	72,091	88.8%	9096	11.2%
light	30,694	89.9%	3431	10.1%
medium	189,526	92.0%	16,581	8.0%
spotting	10,659	83.3%	2138	16.7%
Painful periods
No	201,654	89.6%	23,401	10.4%
Yes	101,317	92.8%	7845	7.2%
Contraception
Hormonal	40,036	85.5%	6787	14.5%
Non hormonal	74,118	93.2%	5386	6.8%
None	188,817	90.8%	19,073	9.2%

Differences by ethnicity were statistically significant but modest, with uncertainty ranging from 7.8% to 9.6% across groups (χ² = 99.9, p < 0.001) (Table 3).

Participants reporting painful periods were more likely to report knowing their period length than those who don’t experience pain (92.8% vs. 89.6%; χ² = 894, p < 0.001). When assessing bleeding pattern, participants who experienced spotting were most likely to report uncertainty regarding period length (16.7%) (Table 3).

Women who had previously been pregnant were slightly less likely to know their period length compared with those who had never been pregnant (90.4% vs. 91.0%; χ² = 394, p < 0.001). Those who were actively trying to conceive had the highest awareness (92.2% knew their period cycle length) (Table 3).

Women using hormonal contraception reported the highest uncertainty (14.5%), more than double the rate of non-hormonal contraception users (6.8%) (χ² = 2902, p < 0.001). Those using no contraception had an uncertainty rate of 9.2%.

Concordance between perceived cycle regularity and reported cycle length

Among participants who described their menstrual cycles as regular and reported knowing their cycle length (n = 200,604), the majority (95.1%) reported cycle lengths within the 21–35 day range, while 4.9% reported cycle lengths outside this range (Table 4). This indicates a high overall concordance between perceived cycle regularity and reported cycle length across the cohort.

Table 4.

Cycle regularity and length awareness among participants. This table examines participants who described their cycles as regular and knew their cycle length, categorising them by whether their cycles fell within the clinically regular range (21–35 days) or outside of it. Data is categorised by age, ethnicity, pregnancy history, reproductive conditions, archetype classification, and contraception use, offering insights into menstrual cycle patterns among different demographic groups

	Described cycles as regular and knew cycle length (n = 200,604)
	21–35 days		Outside of clinically regular range
Age	Frequency	Proportion of group	Frequency	Proportion of group
< 25	30,766	92.8%	2390	7.2%
26–30	60,154	95.3%	2951	4.7%
31–35	60,530	96.0%	2499	4.0%
36–40	28,163	95.7%	1263	4.3%
41–45	9711	94.4%	580	5.6%
45+	1503	94.2%	93	5.8%
Ethnicity
Asian	12,717	94.5%	744	5.5%
Black	7868	93.6%	538	6.4%
Mixed	8036	95.4%	389	4.6%
Other	6084	94.9%	325	5.1%
White	156,123	95.3%	7780	4.7%
Previous pregnancy	970 skipped this question
Yes	71,509	95.6%	3291	4.4%
No	118,468	95.1%	6146	4.9%
Reproductive conditions
Yes	161,331	95.1%	8247	4.9%
No	29,496	95.1%	1533	4.9%
Archetype
Planning for the future	82,091	94.8%	4484	5.2%
Perimenopausal	551	94.0%	35	6.0%
Menopausal	366	97.6%	9	2.4%
Just curious	51,759	95.2%	2610	4.8%
Experiencing symptoms	32,652	96.4%	1212	3.6%
Actively trying to conceive	58,407	96.8%	1915	3.2%
Suspected perimenopause	12,384	96.1%	500	3.9%
Contraception
Hormonal	18,831	88.3%	2506	11.7%
Non hormonal	49,990	96.7%	1680	3.3%
None	122,006	95.6%	5594	4.4%

Concordance varied by age (χ² = 546, p < 0.001). Participants under 25 years were more likely to report cycle lengths outside the 21–35 day range despite describing their cycles as regular (7.2%), compared with participants aged 31–35 years (4.0%). A modest increase was observed among participants aged 45 years and older (5.8%) (Table 4).

Small but statistically significant differences were observed across ethnic groups (χ² = 61.8, p < 0.001), with proportions reporting cycle lengths outside the 21–35 day range ranging from 4.6% to 6.4% across groups (Table 4).

Participants who had previously been pregnant showed slightly higher concordance between perceived regularity and reported cycle length compared with those who had never been pregnant (χ² = 1,288, p < 0.001). In contrast, a self-reported diagnosis of a reproductive health condition was not associated with differences in concordance (χ² = 0.321, p = 0.571).

Concordance also varied by archetype, participants actively trying to conceive demonstrated the highest concordance (96.8%), while participants identifying as perimenopausal showed lower concordance (94.0%) (Table 4).

Discussion

Principal findings

This study presents the largest UK-based analysis of how women understand and report their menstrual cycle characteristics.

Substantial gaps in self-awareness were observed across the cohort. More than one in five participants were unable to report their cycle length, with uncertainty highest among women under 25 years, where one in three did not know their cycle length. Although awareness improved with age, a modest decline was observed after age 45.

Among participants who described their cycles as regular and reported a cycle length, 4.9% reported cycle lengths outside the clinically regular ranges of 21–35 days. This reflects discordance between perceived cycle regularity and reported cycle length, highlighting variation in how individuals might interpret what constitutes a regular cycle. Discordance was most pronounced among younger women, who also showed the lowest overall cycle self-awareness. Together, these findings suggest that many individuals may lack a clear framework for interpreting their menstrual patterns, particularly early in adulthood.

Education, expectations, and interpreting “regularity”

Despite the formal inclusion of menstrual health education in the UK curriculum in 2019 [21], evidence consistently indicates that delivery remains fragmented. Studies report that over one fifth of girls in the UK first learn about menstruation only after menarche [22]. Furthermore, a national survey of teachers reported that only 63% deliver lessons on the menstrual cycle at all; where teaching does occur, it predominantly focuses on biological mechanisms, with limited attention given to lived experiences of menstruation or guidance on how to interpret cycle patterns over time [23].This suggests that a substantial proportion of students may receive little or no structured menstrual education at all.

Consistent with this, many young women describe school-based education as insufficient in timing, depth, and practical relevance. As highlighted by Roux and colleagues [24], practical understanding of menstrual health requires a solid foundation in biological knowledge alongside guidance on how this knowledge can be used to interpret real-life menstrual experiences. The uncertainty observed in the present study supports the need for educational approaches that integrate physiology with practical cycle interpretation.

Early educational framing may also contribute to later discordance in how menstrual regularity is understood. The 28-day cycle is commonly presented as the average length [6], often without adequate emphasis on the wide range of normal intra- and inter-individual variation. In the absence of continued education, individuals may internalise the 28-day cycle as a benchmark for regularity [8, 9]. This may lead some to perceive their cycles as irregular when they deviate from this average.

Owing to gaps in structured education, many individuals report turning to informal sources, a UK based study asked a total of 140 young women, where the mean age of survey respondents was 21.9 (SD ± 1.8) years to rank where they had learned the most about their periods, mothers were most frequently identified as the primary source (60%), followed by the internet (29.8%), friends (15%), social media (6.4%), and lastly school-based education (5%) [16]. Similarly, the WHSS found women more likely to rely on informal sources like their friends and family (74%), Google (71%), the internet (59%) than on GPs/other healthcare professionals (59%) or official NHS resources (54%) for health information [25]. Reliance on informal sources may impact menstrual understanding depending on the accuracy and framing of information accessed [26].

Age and the impact of reproductive lifestage

Menstrual cycle self-awareness in this study improved through the 30s, likely reflecting increased engagement with reproductive healthcare during fertility planning or pregnancy-related care [27, 28]. This pattern is consistent with broader shifts described in the WHSS, where women aged 18–29 most commonly prioritised gynaecological concerns, while those aged 30–39 were more likely to focus on fertility and pregnancy [25]. In our cohort, pregnancy and attempts to conceive appeared to be important drivers of menstrual cycle self-awareness: women who had previously been pregnant were more likely to report knowing their cycle length (79.2%) than those who had never been pregnant (77.2%), and those actively trying to conceive demonstrated the highest awareness (82.5%). This aligns with evidence that engagement with healthcare services during preconception and antenatal care can increase attention to menstrual and reproductive health [29].

However, these patterns also highlight an important limitation in how menstrual cycle awareness is often acquired reactively, prompted by fertility-related goals rather than integrated as part of routine health understanding. Individuals who are not actively planning pregnancy may therefore have fewer prompts from education or healthcare to develop awareness of their cycle patterns, reinforcing the perception that cycle tracking is mainly relevant for conception [27, 28, 30]. This fertility-linked framing is also reflected in menstrual tracking behaviours more widely, period-tracking application use is concentrated in reproductive-age groups and is often oriented toward fertility-related purposes [31]. For example, a large-scale study of over 98,000 users reported that 70% were aged 25–34, suggesting that engagement with tracking tools may contribute to age-related improvements in menstrual cycle awareness during the 30s [32].

Awareness declined again after age 45, likely reflecting increasing cycle variability during the perimenopausal transition, alongside limited accessible education addressing midlife menstrual changes [33, 34]. Taken together, these findings mirror earlier research showing lower awareness of fertility and ovulation among younger women [35], while also reinforcing evidence that gaps in menstrual self-awareness can persist across adulthood [13, 23, 28, 36].

Disparities in menstrual cycle self-awareness and healthcare engagement

While previous research attributes variations in menstrual cycle awareness to cultural attitudes toward menstruation [36], our findings indicate that ethnicity had minimal differences in menstrual cycle self-awareness. However, variation was observed in the concordance between perceived cycle regularity and reported cycle length. For example, Black participants showed slightly higher awareness of cycle and period length overall, yet al.so demonstrated higher discordance between perceived regularity and reported cycle length compared with other groups. This pattern may reflect broader systemic issues within the healthcare systems, rather than individual misunderstanding. Women from minority ethnic backgrounds are more likely to report feeling dismissed when raising reproductive health concerns [37]. If cycle irregularities are normalised or minimised during healthcare interactions, individuals may reasonably come to interpret their own cycles as normal, even when they fall outside clinical guidelines [38–40].

Our findings also indicate that individuals with self-reported diagnosed reproductive health condition(s) were less likely to be unsure of their cycle length than those without a diagnosis (21.2% vs. 26.2%). This likely reflects increased engagement with healthcare services, symptom monitoring, or clinician-led advice to observe and track cycle patterns as part of diagnosis and management [41, 42]. Symptoms experienced further shaped awareness, participants reporting painful periods were more likely to know their period length than those without. This aligns with previous research suggesting that pain acts as a prompt for closer cycle monitoring to manage symptoms [43].

Lower menstrual cycle awareness among hormonal contraception users could be influenced by the fact that hormonal contraceptives suppress ovulation and modify endogenous hormonal signalling, meaning users do not experience a menstrual cycle in the conventional sense and where bleeding occurs, it typically reflects withdrawal bleeding. As a result, menstrual cycle length and regularity may be less applicable and may not be routinely monitored due to reduced perceived need for tracking [44, 45]. The greater uncertainty reported therefore may not indicate poorer understanding, but rather the absence of a cyclical pattern to track.

Implications for reproductive health and healthcare engagement

These findings highlight a broader pattern in how menstrual cycle self-awareness is acquired and applied across the life course. Rather than being embedded as a routine component of health education, it often develops reactively, prompted by fertility planning, pregnancy, or symptom management [46–48]. This reactive pathway may contribute to uncertainty around what constitutes a normal variation, making abnormalities such as irregular periods, heavy bleeding, etc. more likely to be overlooked. Delays in symptom recognition are well documented for conditions such as polycystic ovary syndrome and endometriosis, where prolonged diagnostic timelines are associated with poorer quality of life [10, 49, 50].

Barriers to open patient–provider communication further compound these challenges. National data indicates that 77% women feel uncomfortable discussing menstrual health with healthcare professionals, and four in five report feeling unheard during consultations, particularly when discussing menstrual symptoms [25]. Such experiences may discourage help-seeking, prolong diagnostic pathways, and reinforce uncertainty around symptom significance, contributing to dissatisfaction with care and the continued marginalisation of menstrual health [51].

Strategies to improve menstrual health awareness

Breaking the cycle of misinformation necessitates evidence-based, stigma-free, and age-appropriate education that positions menstrual health as a core component of overall health [52, 53]. School-based interventions that integrate biological foundations with applied interpretation have shown promise. For example, Roux et al., demonstrated the effectiveness of a comprehensive programme combining menstrual physiology with practical application and peer-based teaching involving medical students [15]. Such approaches support sustained learning beyond isolated lessons.

Digital health technologies, including period-tracking applications, are increasingly used to support menstrual awareness, particularly among younger populations. While these tools may improve awareness and symptom tracking [47, 54], many widely used applications rely on simplified algorithms, provide limited educational content, and generate inaccurate cycle predictions, particularly for individuals with irregular cycles [55]. Concerns regarding clinical validity, transparency, regulation, and data privacy further complicate their integration into healthcare pathways [46, 54]. Realising the potential of digital tools will require prioritising accuracy, educational depth, clinical relevance, and ethical governance over engagement-driven design [47, 56]. Web-based educational resources have also shown to improve menstrual health awareness, symptom management and encourage timely engagement with healthcare services when needed [55, 56].

Healthcare professionals also play a crucial role in reshaping how menstrual health is addressed. Studies indicate that limited menstrual understanding correlates with increased distress and reluctance to seek medical advice, particularly when individuals feel dismissed during consultations [25]. While older women generally report greater confidence discussing menstrual well-being with healthcare professionals, younger women may be less likely to raise symptoms, underscoring the importance of early education and supportive clinical environments. Integrating routine discussions of menstrual cycles into healthcare encounters, beyond fertility-focused contexts, may help normalise these conversations, facilitate earlier identification of concerns, and strengthen patient–provider trust [57].

Without coordinated improvements across education, digital health, and clinical practice, misunderstandings about menstrual health are likely to persist, leaving many individuals inadequately supported in both healthcare settings and everyday life.

Study limitations

This study has several limitations that should be considered when interpreting the findings. First, reliance on self-reported data introduces the potential for recall bias and inaccuracies in reported menstrual cycle characteristics. In addition, participants were self-selected, and many may have already identified or suspected a menstrual health concern prior to considering testing. As a result, this cohort is likely to be more self-aware and engaged with menstrual health than the general population. Findings therefore may not be fully generalisable to the wider UK population or to individuals in other countries, particularly given known socioeconomic disparities in access to menstrual health education and healthcare.

Second, the Online Health Assessment (OHA) used in this study was not designed or validated as a comprehensive instrument for assessing menstrual health knowledge or literacy. As such, responses reflect participants’ self-reported perceptions of their menstrual cycle characteristics rather than objective knowledge or clinically verified accuracy. Moreover, the scope of menstrual health literacy assessed was limited; important domains such as menstrual flow volume, cycle-to-cycle variability, knowledge of ovulation and fertile windows, and use of ovulation detection methods were not evaluated. Future research should incorporate validated, multidimensional measures of menstrual and reproductive health literacy, alongside objective cycle tracking data where feasible, and examine intersectional factors such as education level, healthcare access, and cultural influences.

Third, the absence of qualitative data restricts insight into why some participants were uncertain about their cycle characteristics or why discordance was observed between perceived cycle regularity and reported cycle length. Without contextual information on lived experiences, educational exposure, or healthcare interactions, it is not possible to determine the relative contributions of misinformation, educational gaps, healthcare engagement, or normal biological variability. Future studies incorporating qualitative methodologies would help contextualise these patterns and provide a more nuanced understanding of menstrual cycle awareness.

Conclusion

This study provides one of the most comprehensive UK-based assessments of self reported menstrual cycle self-awareness among adult women, revealing substantial gaps in understanding of personal cycle characteristics, particularly among younger individuals. Discordance between perceived cycle regularity and reported cycle length highlights ongoing uncertainty around how menstrual patterns are interpreted. These findings underscore the need to move beyond fertility-focused framings and position menstrual cycle awareness as a core component of lifelong health. Strengthening menstrual education across the life course, improving engagement with healthcare services, and developing digital health tools that prioritise accuracy, education, and ethical governance may support earlier recognition of abnormalities and more timely reproductive healthcare engagement.

Authors’ contributions

ZA, HON, EW, NG, SM and SM were involved in the conception, planning, and writing of the manuscript. EW and LL contributed to data analysis and visualisation. All the authors reviewed and approved the final version of the manuscript.

Funding

This study was funded by Hertility Health.

Data availability

The datasets generated and analysed during this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

As it was a retrospective study, it was not subject to external peer review by the funding body or a patient and public involvement panel.

Consent for publication

At the time of onboarding, all participants were asked if they consented to their data being used for research and publication. Only those who provided consent were included in this analysis.

Competing interests

HON and NG are co-founders of Hertility Health. ZA, EW, SM and LL are employees of Hertility Health. SM and SM are consultants at Hertility Health.