. 2021 Sep 30;64(12):2609–2652. doi: 10.1007/s00125-021-05568-3

Table 4.

Non-glycaemic factors that alter HbA_1c levels [70]

Effect on HbA_1c	Factor
Apparent increase	• Age • Ethnicity: HbA_1c is slightly higher in African Americans than in people of White Northern-European ancestry^a • Anaemias with decreased erythrocyte turnover: iron, vitamin B₁₂, folate • Severe hypertriglyceridaemia (hypertriacylglycerolaemia) • Severe hyperbilirubinaemia • Chronic alcohol consumption • Chronic salicylate consumption • Chronic opioid ingestion
Apparent decrease	• Pregnancy (second and third trimester) • Anaemias of chronic disease • Haemolytic anaemia • Splenomegaly and splenectomy • Acute blood loss • Renal failure • Advanced liver disease drugs: dapsone; trimethoprim/sulfamethoxazole • Vitamin E ingestion • Ribavirin and interferon alpha • Erythrocyte transfusion
Apparent increase or decrease	• Haemoglobin variants • Vitamin C ingestion

Effect on HbA_1c

Factor

Apparent increase

• Age

• Ethnicity: HbA_1c is slightly higher in African Americans than in people of White Northern-European ancestry^a

• Anaemias with decreased erythrocyte turnover: iron, vitamin B₁₂, folate

• Severe hypertriglyceridaemia (hypertriacylglycerolaemia)

• Severe hyperbilirubinaemia

• Chronic alcohol consumption

• Chronic salicylate consumption

• Chronic opioid ingestion

Apparent decrease

• Pregnancy (second and third trimester)

• Anaemias of chronic disease

• Haemolytic anaemia

• Splenomegaly and splenectomy

• Acute blood loss

• Renal failure

• Advanced liver disease drugs: dapsone; trimethoprim/sulfamethoxazole

• Vitamin E ingestion

• Ribavirin and interferon alpha

• Erythrocyte transfusion

Apparent increase or decrease

• Haemoglobin variants

• Vitamin C ingestion

^aVariability within races is greater than variability between races [293]