HbA1c

Causes of Falsely Elevated HbA1c

• Decreased RBC turnover or prolonged RBC lifespan

  • Iron deficiency anaemia (IDA)

  • Vitamin B12 deficiency or folate deficiency

  • Chronic alcohol intake can reduce RBC turnover

  • Some haemoglobin variants can interfere with certain assay methods

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Causes of Falsely Reduced HbA1c

• Increased RBC turnover or shortened RBC lifespan

  • Haemolytic anaemia (e.g. autoimmune, microangiopathic)

  • Sickle cell disease or thalassaemia (abnormal haemoglobin variants)

  • Splenomegaly (increased RBC destruction)

  • Recent acute or chronic blood loss

  • Recent blood transfusion (dilutes the patient’s haemoglobin pool)

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Notes:

• HbA1c may be unreliable in conditions that significantly alter RBC lifespan, including advanced liver or renal disease

• During the first 4 weeks of pregnancy, HbA1c does not accurately reflect glycaemic control due to dynamic changes in haemodilution and red cell turnover

• Consider alternative glucose monitoring (e.g. fructosamine) when HbA1c may be inaccurate

• Laboratory assays differ in their susceptibility to interference from uncommon haemoglobin variants (check local lab methods if suspicion arises)

• Conversion between % and mmol/mol (IFCC units) is essential (e.g. 7% ≈ 53 mmol/mol)

• Evaluate for iron deficiency or haemolysis if discordance between measured HbA1c and average home blood glucose levels is suspected

• Always correlate HbA1c with clinical context and other markers (e.g. fructosamine, home BGL readings)

• Investigate for haemolysis, iron deficiency, or haemoglobinopathies if unexplained discrepancies occur

• Use trimester-specific guidelines and validated assays in pregnancy

• In patients with known haemoglobinopathies or RBC disorders, emphasise alternative glycaemic measures like fructosamine or close capillary glucose monitoring