Hidden genetic risk may delay diabetes diagnosis for Black and Asian men
A common but often undiagnosed genetic condition may be causing delays in type 2 diabetes diagnoses, and increasing the risk of serious complications for thousands of Black and South Asian men in the UK, and potentially millions worldwide.
Findings from a collaborative study by Exeter University and The Wolfson Institute of Population Health (Queen Mary University of London) show that around one in seven Black men and one in 63 Asian men in the UK carry the G6PD deficiency genetic variant. While G6PD deficiency does not cause diabetes, it makes results on the widely used HbA1c blood test for diabetes appear artificially low. This can mislead doctors and patients, resulting in delayed diabetes diagnosis and treatment. Men with G6PD deficiency are diagnosed with type 2 diabetes on average four years later than those without the variant, but despite this, fewer than one in 50 have been diagnosed with the condition. The study also found that men with G6PD deficiency are at a 37% higher risk of developing diabetes-related microvascular complications, such as eye, kidney, and nerve damage, compared with other men with diabetes.
The findings are based on genetic and health data from over half a million people in UK Biobank and Genes & Health studies. The research was conducted by a multidisciplinary team of clinicians and scientists, with the support of community partners who linked the genetic data from each participant to their medical information.
G6PD deficiency affects more than 400 million people worldwide, and is especially prevalent among those with African, Asian, Middle Eastern, and Mediterranean backgrounds. It is more common in men, and usually goes undetected because it rarely causes symptoms. The World Health Organization recommends routine screening for G6PD deficiency in populations where it is common, but this is not widely implemented in the UK or many other countries.
Veline L’Esperance, GP and WIPH Senior Clinical Research Fellow, said:
“These findings are deeply concerning because they show how a widely used diagnostic tool may be failing communities that are already disproportionately affected by type 2 diabetes. Too many people are being left undiagnosed until it is too late to prevent serious complications. We need greater awareness among healthcare professionals and stronger policies to ensure equitable screening and diagnosis. That is why we are launching ‘Black Health Legacy’, which aims to be the largest health research programme focused on tackling diseases that disproportionately affect people from Black backgrounds. This is about saving lives and tackling long-standing inequalities in our healthcare system.”
Dr Esther Mukuka, Director of Research Inclusion at the NIHR, said: "At NIHR, we are committed to ensuring research drives fairer healthcare for all. Addressing the impact of G6PD deficiency on diabetes testing is an important step towards reducing inequalities and making sure that everyone, regardless of background, benefits equally from medical advances."
The study was supported by the National Institute for Health and Care Research Exeter Biomedical Research Centre and funded through a Wellcome Discovery Award.
Susan Martin, Miriam Samuel, Daniel Stow, Alys M. Ridsdale, Ji Chen, Katherine G. Young, Harry D. Green, Genes & Health Research Team, Andrew T. Hattersley, Veline L’Esperance, Trevelyan J. McKinley, Sarah Finer and Inês Barroso. Undiagnosed G6PD deficiency in Black and Asian individuals is prevalent and contributes to health inequalities in type 2 diabetes diagnosis and complications. Diabetes Care. 30 Sept 2025. https://diabetesjournals.org/care/lookup/doi/10.2337/dc25-0556