Random Blood Glucose: Episode 2

There are many numbers to keep in mind when we help people with diabetes manage their condition. Some are diagnosis criteria, others are therapeutic targets, and still others are related to specific treatments. Although these numbers may seem random or arbitrary to some of our patients, they are evidence based and derived from data related to diabetes pathophysiology and the prevention of complications. This article is part of a series explaining some of the key numbers related to diabetes management and summarizing the evidence underpinning them.

The first three articles in this series (1–3) focused on A1C-related numbers discussed in the American Diabetes Association’s (ADA’s) Standards of Care in Diabetes—2024. We then moved on to discuss plasma glucose numbers, starting with an article on fasting plasma glucose (4) and then postprandial glucose (5). In the last issue, we began a discussion of the significance and supporting evidence of different random blood glucose (RBG) values from the ADA’s Standards of Care in Diabetes—2025 (6). In this issue, we continue that discussion. Any blood glucose values or ranges that are not specifically described as fasting or postprandial will be discussed as RBG metrics.

RBG: Episode 2

≥200 mg/dL

Significance of this blood glucose value

1. RBG ≥200 mg/dL is one of the criteria to diagnose diabetes when a person has symptoms of hyperglycemia.

2. This RBG range is also one of the diagnosis criteria for diabetic ketoacidosis (DKA).

Supporting evidence

1. To diagnosis diabetes, repeat testing either by two different tests or one test at two different times is needed, except when a person exhibits classic hyperglycemic symptoms such as polyuria, polydipsia, unexplained weight loss, or hyperglycemic crisis. In the presence of those symptoms, the person can be diagnosed with diabetes if the RBG value is ≥200 mg/dL. Checking plasma glucose in the presence of symptoms not only confirms that symptoms are caused by diabetes, but may also guide treatment decisions. Analysis of three cross-sectional epidemiological studies showed a linear increase in diabetic retinopathy when a 2-hour postprandial glucose level is >200 mg/dL (7). RBG technically is not a 2-hour postprandial glucose value; however, the same value is used along with the presence of symptoms because this value is associated with increased risk of complications.

2. DKA diagnosis criteria traditionally have included a blood glucose range indicative of hyperglycemia, along with indicators of acidosis and ketosis. A blood glucose level >250 mg/dL previously was considered indicative of hyperglycemia, but that value was recently reduced to ≥200 mg/dL. A recent multi-organizational consensus statement (8) recommended this change and also recommended that, even if blood glucose is <200 mg/dL, a history of diabetes is enough to satisfy the diabetes/hyperglycemia criterion for diagnosing DKA. The main reason behind these changes is the increasing prevalence of euglycemic DKA. Approximately 10% of people with DKA have blood glucose levels <200 mg/dL in the presence of ketosis and acidosis, leading to diagnosis of euglycemic DKA (9–11). Euglycemic DKA has various etiologies, including exogenous insulin injection, reduced food intake, pregnancy, impaired gluconeogenesis resulting from alcohol use, liver failure, and use of sodium–glucose cotransporter 2 (SGLT2) inhibitors. The recently expanding use of SGLT2 inhibitors in people with type 1 or type 2 diabetes has accounted for the majority of euglycemic DKA cases (8).

>250 mg/dL

Significance of this blood glucose range

1. This glucose range defines level 2 hyperglycemia in the ambulatory glucose profile (AGP) reports of continuous glucose monitoring (CGM) systems.

2. This range is also used as an indicator of marked hyperglycemia in youth with hyperglycemic symptoms, with a recommendation to initiate long-acting insulin along with metformin initiation and titration.

3. Glucose values up to this range may be acceptable in certain hospitalized patients with a high risk of hypoglycemia or short life expectancy.

4. This range is also recommended as an alert with regard to elderly people with diabetes who are being admitted to a post-acute and long-term care (PALTC) setting.

Supporting evidence

1. This blood glucose range marks the cutoff point between the first and second levels of time above range (TAR) on CGM AGP reports. Level 2 TAR indicates urgency for action to reduce clinically significant high blood glucose (12). Although evidence examining the impact of hyperglycemia does not examine the effect of incremental increases in blood glucose levels, values ≥250 mg/dL are traditionally associated with DKA, and A1C levels that correspond to that level of hyperglycemia are associated with increased risk of complications (13).

2. When youth who are recently diagnosed with type 2 diabetes have typical hyperglycemic symptoms such as polyuria, polydipsia, nocturia, and/or weight loss, a blood glucose level >250 mg/dL is the recommended point at which to start insulin, even if there is no acidosis and the possibility of type 1 diabetes is ruled out (14). This glucose range is considered to be a marker of marked hyperglycemia requiring insulin to treat glucose toxicity. In addition to starting insulin, it is also recommended to initiate and titrate metformin, unless there is ketosis or ketoacidosis, in which case initiation of metformin must be postponed until the ketosis or ketoacidosis is resolved. Metformin is considered a first-line therapy in youth with type 2 diabetes. In the TODAY (Treatment Options for Type 2 Diabetes in Adolescents and Youth) study, half of the participants maintained durable glycemic control with an A1C <8% with metformin therapy alone (15). The RISE (Restoring Insulin Secretion) Consortium study did not demonstrate differences in measures of glucose or preservation of β-cell function between individuals taking metformin and those taking insulin, but there was more weight gain with insulin (16).

3. Hyperglycemia in the hospital setting is associated with increased mortality and morbidity. Although a tighter blood glucose range has been generally recommended in hospitalized patients with hyperglycemia, a blood glucose range of up to 250 mg/dL may be acceptable in certain individuals such as those who are terminal with a short life expectancy, have advanced kidney failure and/or are on dialysis, have a high risk for hypoglycemia, and/or have labile glycemic excursions. In these individuals, the goal of managing glycemia is to maintain blood glucose with less aggressive goals that would help avoid symptomatic hypoglycemia and hyperglycemia.

4. Unlike hospital settings, elderly patients admitted in PALTC settings are not evaluated on a daily basis. According to federal guidelines, assessment is required every 30 days in the first 90 days, followed by once every 60 days or as clinically indicated. In practice, although individuals may be seen more frequently than the federal minimal requirement, there is concern that some people may have poor glycemic control or experience wide glycemic variability without their health care provider (HCP) being aware of the situation. It is recommended to contact the HCP as soon as possible when blood glucose values are high or low. Two or more glucose values ≥250 mg/dL within 24 hours with a significant change in clinical status, consistent blood glucose levels >250 mg/dL within 24 hours, and consistent blood glucose values >300 mg/dL on 2 consecutive days are included as high blood glucose alerts that warrant urgent communication to the HCP.

300 mg/dL

Significance of this blood glucose range

At this blood glucose value, initiation of insulin should be considered in adults with type 2 diabetes.

Supporting evidence

It is common practice to initiate insulin in people with diabetes who have symptoms of hyperglycemia, especially with evidence of catabolism and severe hyperglycemia regardless of background treatment. The main reason for using insulin for severe hyperglycemia is to reverse glucose toxicity. Chronic elevation in the plasma glucose concentration leads to progressive impairment in insulin secretion and may contribute to insulin resistance. Additionally, people with poorly controlled type 1 diabetes have insulin resistance that can be reversed with tighter glucose control. This may explain the so-called honeymoon period commonly seen in newly diagnosed patients with type 1 diabetes after initiation of insulin therapy (17).

After glucose toxicity resolves, individuals without insulin deficiency should be switched to noninsulin therapy. There is emerging evidence that people with type 2 diabetes who have severe hyperglycemia can be treated successfully with a sulfonylurea, a glucagon-like peptide 1 (GLP-1) receptor agonist, or a dual GLP-1/glucose-dependent insulinotropic polypeptide receptor agonist, although evidence is scarce for individuals with a baseline A1C >10–12% (18–21).

≥350 mg/dL

Significance of this blood glucose value

This is the glucose range at which children with type 1 diabetes should postpone engaging in intensive physical activity.

Supporting evidence

The type, intensity, and duration of exercise is shown to affect blood glucose levels both during and after exercise. Intensive aerobic activity can cause hyperglycemia that can last for a few hours, but it can also increase the risk of nocturnal hypoglycemia. Hyperglycemia can occur before, during, and after exercise, and it is important to ensure that hyperglycemia is not related to insulin deficiency in youth with type 1 diabetes, which can lead to the development of DKA.

The ADA recommends postponing any intensive physical activity if there is marked hyperglycemia with blood glucose values ≥350 mg/dL, moderate to large urine ketones, and/or β-hydroxybutyrate (B-OHB) >1.5 mmol/L. A 2017 consensus statement on exercise in type 1 diabetes (22) recommends checking ketones when the blood glucose level is >270 mg/dL with no explanation (e.g., unrelated to a recent meal). If B-OHB is >1.5 mmol/L, any exercise is contraindicated. When B-OHB is elevated moderately (up to 1.4 mmol/L), exercise should be restricted to a light intensity for only a brief duration (<30 minutes), and a small correction insulin dose might be needed before starting the exercise. When B-OHB is <0.6 mmol/L, mild to moderate aerobic exercise can be started, but caution should be taken for intensive activity, which can further increase the blood glucose level.

>360 mg/dL

Significance of this blood glucose value

This blood glucose value at the time of diagnosis is one of the useful factors in diagnosing type 1 diabetes.

Supporting evidence

No single clinical feature in isolation confirms a diagnosis of type 1 diabetes; however, there are a few clinical features that indicate the possibility of type 1 diabetes. A blood glucose level >360 mg/dL at the time of diagnosis, along with other features such as young age of presentation (<35 years), low BMI (<25 kg/m²), unintentional weight loss, and ketoacidosis, are considered to be strong indicators, whereas the presence of ketosis without acidosis, osmotic symptoms, family history, or a history of autoimmune diseases are weak discriminators. One study found that blood glucose >360 mg/dL has a high specificity of 76.3% and a sensitivity of 51.5% in predicting type 1 diabetes (23).

≥600 mg/dL

Significance of this blood glucose value

The blood glucose value is one of the criteria for diagnosing hyperosmolar hyperglycemic syndrome (HHS).

Supporting evidence

In HHS, there is less severe insulin deficiency compared with DKA. People with HHS have sufficient insulin to prevent ketosis, but not enough to prevent hyperglycemia. Without ketosis, these individuals have higher blood glucose levels over a longer period of time, and hyperglycemia leads to osmosis diuresis, resulting in dehydration and hemoconcentration. When fluid intake is insufficient, hyperosmolarity develops and mental status changes occur. Typically, people with HHS who are admitted to the hospital have much higher blood glucose levels, along with hyperosmolarity without acidosis or ketosis. Blood glucose levels ≥600 mg/dL are the usual criterion for severe hyperglycemia in an HHS diagnosis (8).