HbA1c-only diagnosis may misclassify diabetes in India, Lancet warns

A standard blood test that forms the basis of diabetes diagnosis, insurance assessments and public health surveys in India may be giving misleading results for large sections of the population, a new analysis published in Lancet Regional Health, Southeast Asia has warned.

The paper raises concerns over the widespread use of HbA1c, the most common test used to diagnose and monitor diabetes, saying its accuracy can be affected in populations with high levels of anaemia, inherited blood disorders and G6PD deficiency, all of which are common in India. G6PD deficiency is a genetic blood disorder in which red blood cells break down faster than normal, potentially leading to falsely low HbA1c readings and delayed diabetes diagnosis. The findings could have implications for patient care as well as for how India estimates the scale of its diabetes burden.

India is home to an estimated 10.1 crore people living with diabetes and another 13.6 crore with prediabetes, according to the ICMR–INDIAB study. Any systematic error in diagnosis therefore affects disease estimates and treatment decisions at a population scale.

“HbA1c is widely used because it is simple and convenient, but when relied on alone it can misclassify patients,” said Anoop Misra, chairman of Fortis C-DOC Centre of Excellence for Diabetes and the paper’s corresponding author. “Some patients may be diagnosed late, while others may receive treatment they do not yet need.”

HbA1c estimates average blood sugar by measuring how much glucose is attached to haemoglobin in red blood cells. The authors pointed out that conditions that affect haemoglobin levels or the life span of red blood cells such as iron-deficiency anaemia or haemoglobin disorders can distort results. According to the National Family Health Survey-5 (NFHS-5), more than 57% of women and about 25% of men in India are anaemic, increasing the risk of inaccurate HbA1c readings across large sections of the population.

The analysis also notes that men with undetected G6PD deficiency could see diabetes diagnosis delayed by up to four years if HbA1c alone is used, increasing the risk of complications and higher long-term treatment costs. Variations in laboratory quality and testing standards across the country further add to the problem.

“Even in well-equipped urban hospitals, HbA1c readings can be influenced by blood cell variations and inherited disorders,” said Shashank Joshi, a Mumbai-based endocrinologist and co-author. “In rural and tribal areas, where anaemia is more common, the gaps between test results and actual blood sugar levels may be wider.”

The paper also flags risks for public health planning. Surveys and screening programmes that rely only on HbA1c may either overstate or understate the true prevalence of diabetes, potentially affecting policy decisions, healthcare spending and investment planning.

The authors recommend a more practical, setting-specific approach to diagnosis and monitoring. In low-resource settings, they suggest oral glucose tolerance tests along with periodic self-monitoring of blood glucose and basic blood tests. In tertiary hospitals, HbA1c should be used alongside glucose tolerance tests, continuous glucose monitoring and alternative markers such as fructosamine.

“Using a combination of tests gives a clearer picture of blood sugar control,” said Shambho Samrat Samajdar, another co-author. “This is important for clinical decisions as well as for planning health resources.”

The findings come at a time when India’s diabetes care market covering drugs, devices and diagnostics was valued at about $4.8 billion (approximately ₹39,000 crore) in 2024, according to IMARC Group. Within this, the HbA1c testing segment is expanding rapidly. As per industry estimates by Mobility Foresights, India’s HbA1c testing market is projected to grow from about $1.98 billion to nearly $3.9 billion over the next few years, driven by increased screening and routine monitoring.

While HbA1c will remain a key test, the authors caution that over-reliance on a single biomarker in a country with over 10 crore diabetics could carry hidden clinical as well as economic costs.

Other contributors to the paper include Dr Naval K Vikram, professor of medicine at All India Institute of Medical Sciences.