HbA1c and anaemia: Why your blood sugar test may not tell the full story

Blood sugar assessments, such as HbA1c, often overlook how anaemia can influence the findings. HbA1c estimates average blood glucose over the past two to three months, relying on red blood cell longevity. Consequently, conditions altering red blood cells could skew this test. This article explores the relationship between anaemia and HbA1c, focusing on its impact, affected types, and alternative glucose assessment methods.

Anaemia, not a singular condition, arises from various causes like iron deficiency, blood loss, and other factors that impact red blood cell production or lifespan. Consequently, an unexpectedly high or low HbA1c may not always accurately reflect a person's glucose levels. Dr Palleti Siva Karthik Reddy, a Consultant Physician at Elite Care Clinic, clarifies that iron-deficiency anaemia may cause an HbA1c to appear higher than actual blood glucose, as red blood cells may stay longer in circulation, accumulating more glycated haemoglobin. This can falsely elevate HbA1c without corresponding blood glucose increases.

Conversely, haemolytic anaemia, recent blood loss, or conditions shortening red blood cell survival can lead to a lower-than-actual HbA1c. Red blood cell disorders, such as sickle cell disease and thalassaemia, can also affect HbA1c interpretation. Doctors should consider a clear mismatch between HbA1c and repeated glucose readings, examining haemoglobin levels, red blood cell indices, and the anaemia's underlying cause before making treatment decisions based solely on HbA1c.

When HbA1c becomes unreliable, doctors can employ alternative glucose assessment methods. These include fasting and post-meal blood glucose measurements, continuous glucose monitoring, or structured home glucose monitoring. Fructosamine or glycated albumin can also provide valuable insights, as they reflect glucose control over a shorter period and are not influenced by red blood cell lifespan. Once the underlying anaemia is identified and treated, HbA1c becomes more reliable.