A large-scale study suggests that changes in gut bacteria could serve as early indicators of type 2 diabetes, potentially enabling earlier interventions than standard blood tests.
A large new analysis suggests that changes in gut bacteria may be visible before blood sugar rises far enough to meet the threshold for type 2 diabetes, raising the possibility that the microbiome could one day help flag risk earlier than standard tests do. The work, presented at the European Association for the Study of Diabetes meeting in Milan, adds to growing evidence that the trillions of microbes in the digestive tract may be tied to how the body handles glucose long before a formal diagnosis is made.
Researchers from the University of Trento and collaborators in the UK examined gut bacterial DNA and health data from 229,025 adults in Britain and the US, according to the study summary. The average participant was about 50 years old, and most had blood sugar levels in the normal range. Within that group, 3,627 people had type 2 diabetes and 14,022 had prediabetes, the stage in which blood sugar is elevated but not yet in the diabetic range.
After accounting for age, sex and body mass index, the team identified 789 bacterial species linked to type 2 diabetes. Of those, 168 were more abundant in people with the disease and 621 were less common. The researchers said 587 of those species were also associated with prediabetes among people not taking diabetes medicines, suggesting the bacterial shifts may begin early in the disease process rather than appearing only after diagnosis.
The study also examined more than 135,000 people whose blood sugar was still considered normal. Those whose glucose remained elevated for longer after eating were more likely to show the same gut bacterial pattern seen in type 2 diabetes. That matters because a prolonged post-meal rise in blood sugar is often one of the earliest signs that the body is becoming less responsive to insulin, the hormone that helps move glucose out of the bloodstream and into cells.
The findings fit with earlier research. A July 2026 report in Medical News Today described a study identifying six bacterial species linked to higher diabetes risk years before diagnosis, while a 2022 paper in Diabetes Care found that gut microbiome composition could predict type 2 diabetes in a Finnish adult cohort. More recent work in Scientific Reports and Cell Reports Medicine has likewise pointed to microbial signatures that may help forecast future disease, although those studies were smaller and used different populations and methods.
Even so, the new analysis does not show that gut bacteria cause diabetes. The association could run in the other direction, with early metabolic changes altering the microbiome, or reflect other influences such as diet. Microbiome testing is therefore not ready to replace blood tests, which remain the standard way to identify prediabetes and diabetes.
Still, the scale of the latest study makes it notable. By pooling data from such a large number of adults, the researchers were able to detect bacterial patterns that smaller studies might miss. If future long-term studies confirm that these microbial signals reliably predict who goes on to develop diabetes, gut testing could eventually help doctors identify higher-risk people sooner and support earlier changes in diet, exercise and other lifestyle habits.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
