‘My blood glucose is always high (160-220) but my HbA1c is always under 6. Why?’

A Quora user asked why someone could have consistently high blood glucose readings of 160-220 mg/dL while still having an HbA1c below 6 percent. Dr Pranav Ghody, an endocrinologist at Wockhardt Hospitals, explained that the two measurements reflect different things. HbA1c measures average glucose over the previous two to three months, while glucose readings are instantaneous.

However, a wide glucose range warrants evaluation, especially if readings are frequently high. Dr Ghody cautioned that an HbA1c can appear lower than actual glucose levels due to red blood cell turnover and destruction. Certain haemoglobin variants can also interfere with HbA1c tests. Doctors would consider factors like anaemia, recent blood loss or transfusion, conditions affecting red cell turnover, kidney disease, and haemoglobin variants when faced with a mismatch.

To resolve the discrepancy, the patient should verify glucose readings with a reliable glucometer or continuous glucose monitor. The doctor may repeat the HbA1c using a suitable lab method and check blood counts and other tests. If HbA1c remains unreliable, alternatives like fructosamine or glycated albumin could provide insight into shorter-term glucose control.

Despite a low HbA1c, a person should not ignore consistently high glucose readings, as persistent hyperglycaemia can have consequences even when the HbA1c appears normal.