A new evidence-based viewpoint published in The Lancet Regional Health: Southeast Asia has raised serious concerns about the reliability of glycated haemoglobin (HbA1c), one of the most widely used laboratory
tests in India for diagnosing and monitoring type-2 diabetes. The study suggests that HbA1c may not accurately reflect true blood glucose levels in large sections of the Indian population, potentially misrepresenting both individual diagnoses and the country’s overall diabetes burden.
HbA1c measures average blood sugar levels over the previous two to three months by estimating the percentage of haemoglobin coated with glucose. Clinically, HbA1c values below 5.7% are considered normal, 5.7–6.4% indicate prediabetes, and values of 6.5% or higher are used to diagnose diabetes. However, the new analysis shows that this metric can produce misleading results in populations with a high prevalence of anaemia, haemoglobinopathies, and red blood cell enzyme disorders such as glucose-6-phosphate dehydrogenase (G6PD) deficiency, conditions that are widespread in India.
The review, published online on February 9, 2026, was led by Anoop Misra, Chairman of the Fortis C-DOC Centre of Excellence for Diabetes, along with collaborators from across India. It challenges the practice of relying on HbA1c as a sole diagnostic or monitoring tool for type-2 diabetes in South Asia.
“Relying exclusively on HbA1c can result in misclassification of diabetes status,” said Professor Misra, the corresponding author. “Some individuals may be diagnosed later than appropriate, while others could be misdiagnosed. This can delay timely treatment, affect disease management, and compromise blood sugar monitoring.”
The problem lies in the biology of HbA1c itself. Because the test depends on haemoglobin, any condition that alters the quantity, structure, or lifespan of red blood cells—such as iron-deficiency anaemia, inherited haemoglobin disorders, or G6PD deficiency—can distort HbA1c values. As a result, HbA1c may either under-estimate or over-estimate actual blood glucose levels.
India is particularly vulnerable to this distortion. In some regions, more than 50% of the population is affected by nutritional iron-deficiency anaemia, according to data cited from 2025. This widespread nutritional challenge can significantly skew HbA1c readings, misleading clinicians during both diagnosis and long-term monitoring of diabetes.
The authors also highlight that men with undiagnosed G6PD deficiency, a condition common in certain Indian populations may experience delays in diabetes diagnosis of up to four years if HbA1c alone is used, increasing the risk of preventable complications.
Shashank Joshi, co-author of the study and head of Joshi Clinic in Mumbai, noted that inaccuracies are not limited to underserved areas. “Even in well-resourced urban hospitals, HbA1c readings can be influenced by red blood cell variations and inherited haemoglobin disorders. In rural and tribal regions, where anaemia and red cell abnormalities are even more common, these discrepancies may be far greater.”
Adding to the challenge is inconsistent laboratory quality control across India, which can further affect HbA1c accuracy. The authors warn that large public health surveys that rely solely on HbA1c may therefore underestimate or misrepresent India’s true diabetes burden, affecting policy planning and healthcare resource allocation.
Shambho Samrat Samajdar, a co-author from Kolkata, stressed the importance of a more comprehensive diagnostic strategy. “Combining the oral glucose tolerance test (OGTT), self-monitoring of blood glucose, and basic haematological assessments provides a more accurate picture of diabetes risk. This approach can refine national estimates and guide better public health decisions.”
To address these challenges, the authors propose a resource-adapted diagnostic and monitoring framework for India:
In low-resource settings:
Diagnosis should rely on the oral glucose tolerance test (OGTT), using two values—fasting glucose and a 2-hour reading after ingesting 75 grams of glucose. Monitoring should include self-monitoring of blood glucose (two to three times per week) combined with basic haematological screening, such as haemoglobin levels and peripheral blood smear.
In tertiary care settings:
HbA1c should be used only in combination with OGTT for diagnosis. For monitoring, continuous glucose monitoring (CGM) and alternative markers such as fructosamine should be considered alongside HbA1c.
When indicated:
Comprehensive iron studies, haemoglobin electrophoresis, and quantitative G6PD testing should be performed to clarify misleading results.
The framework emphasises that diabetes diagnosis and monitoring must be tailored to healthcare resources and individual patient risk factors, especially in populations where anaemia, haemoglobinopathies, and G6PD deficiency are common.
The authors conclude that in countries like India where anaemia from multiple causes is endemic, HbA1c, despite being widely regarded as the gold standard, can yield spurious values. Therefore, it should not be used in isolation and must be combined with other diagnostic and monitoring tools to ensure accurate detection, effective management, and realistic assessment of the nation’s diabetes burden.
