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. Author manuscript; available in PMC: 2012 May 1.
Published in final edited form as: Am J Med. 2011 May;124(5):395–401. doi: 10.1016/j.amjmed.2010.11.025

TABLE 2.

FACTORS THAT AFFECT A1C

  • Abnormal erythrocyte lifespan

    • Hemoglobinopathies3, e.g., thalassemia, hemoglobins S, C, E, D

    • Erythrocyte abnormalities, e.g., spherocytosis

    • Acute blood loss; increased reticulocyte number

    • Iron deficiency may increase A1C due to increased erythrocyte survival

    • Normal variation in erythrocyte lifespan may account for difference in A1C between individuals with the same average BG

  • Assay-related artifacts

    • Carbamylated hemoglobin (e.g., renal failure) increases A1C

    • Acetylated hemoglobin (e.g., aspirin)

    • High hemoglobin F levels increase A1C

    • Hemoglobins S, G, D, C, and E decrease A1C

  • Miscellaneous

    • Vitamins E and C can reduce hemoglobin glycation

    • Hypertriglyceridemia and hyperbilirubinemia may increase A1C

    • Patients receiving anti-retroviral treatment have lower A1C

    • A1C increases with age by up to 0.4%

    • Ethnic differences, e.g., A1C is higher in Afro-Caribbeans by 0.4%

    • A1C is lower in pregnancy by 0.5%

    • Chronic liver disease lowers A1C

  • Fast vs. slow glycosylation: A1C is more closely correlated in monozygotic than in dizygotic twins