In a systematic review of studies, researchers noted that the presence of iron deficiency led to an increase in HbA1c when compared with controls, with no corresponding rise in blood glucose, rendering a diagnosis of diabetes unreliable without further tests.

HbA1c is likely to be affected by iron deficiency and iron deficiency anemia with a spurious increase in HbA1c values, the researchers wrote. This may lead to confusion when diagnosing diabetes using HbA1c. This review clearly identifies the need for more evidence, especially in identifying the types and degrees of anemia likely to have significant impact on the reliability of HbA1c.

Emma English, (PhD, of the University of Nottingham, U.K.), and colleagues analyzed data from 12 cohort studies completed between January 1990 and May 2014 that measured HbA1c and glucose values in nondiabetic, nonpregnant adults aged at least 18 years. Researchers excluded case-control, case report and case series studies.

Most studies linked a high HbA1c level in adults to iron deficiency, when compared with other markers of glycemia, according to researchers; several studies recommended correcting the iron deficiency to help regulate HbA1c levels.

The researchers recommend clinicians consider abnormalities related to iron deficiency when glucose and HbA1c results are different.

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