Your blood type could raise type 2 diabetes risk by 28 percent, research shows

People with blood type B — whether positive or negative — face a 28 per cent higher risk of developing type 2 diabetes compared with those who have non-B blood types, a major 2024 research review has found. The finding is the only association out of 270 examined that survived the most rigorous levels of scientific scrutiny.

The study, published in BMC Medicine, was led by Epidemiologist Fang-Hua Liu of Shengjing Hospital of China Medical University and involved an umbrella review — a large-scale synthesis drawing on 51 systematic reviews with meta-analyses — covering a wide range of health outcomes tied to ABO and Rhesus blood groups.

What the research involved

Human blood is classified into eight main groups based on the sugars and proteins present on the surface of red blood cells. A, B, and AB types carry antigens — sugar molecules capable of triggering an immune response — while O-type blood carries neither A nor B antigens. Rhesus (Rh) factors are proteins that determine blood compatibility and give blood its positive or negative designation.

Previous studies have pointed to these cellular differences as potential markers of disease vulnerability. Liu and colleagues set out to systematically map those links across around 270 distinct health outcomes, drawing on databases including PubMed, Web of Science, Embase, Scopus, Cochrane Library, and several regional sources — searched from inception through to 16 February 2024.

How the evidence was tested

"Numerous systematic reviews with meta-analyses have been published, which explored correlations between ABO and Rhesus blood groups with various health outcomes," the research team wrote. "However, to date, the association between these blood groups and human health outcomes remains controversial. The current umbrella review included 51 systematic reviews with meta-analysis articles with 270 associations."

"We recalculated each association and found only one [instance of] convincing evidence for an association between blood group B and type 2 diabetes mellitus risk compared with the non-B blood group," they added.

Each of the 270 reported associations was put through a series of statistical stress tests. Researchers examined the strength and consistency of findings across studies, assessed whether dataset sizes were sufficient to be reliable, and looked for signs of bias — including small studies inflating their results or an unusually high proportion of positive outcomes. Crucially, they also tested whether each association would be likely to hold up under future research. Most did not pass.

How significant is a 28% higher risk?

On its own, a 28 per cent elevated risk is relatively modest compared with other known diabetes risk factors. Consuming just 50 grams of processed meat per day raises type 2 diabetes risk by 37 per cent. A sedentary lifestyle can increase it by as much as 112 per cent. Being overweight remains one of the single strongest predictors of the condition.

That said, researchers noted the risk increase from blood type B may be enough to tip the balance when other risk factors are already present. The study did not explore the biological mechanism behind the link. A separate 2025 study has suggested the gut microbiome may play a role, though further investigation is needed.

What the findings mean more broadly

The research confirms there is a real, measurable association between blood type and type 2 diabetes — one that individuals can factor into their broader understanding of personal risk. It also highlights gaps and weaknesses in existing blood group research, pointing to the need for more rigorously designed studies to establish how blood type relates to disease outcomes more widely.