Doctors have long used tests like fasting blood sugar and two‑hour glucose readings to find out whether someone is at risk of developing type 2 diabetes.
But a growing number of people who later develop diabetes are never identified early enough, even when their test results look normal.
Now, new research from the University of Tübingen, Helmholtz Munich, the German Center for Diabetes Research, and New York University suggests that an overlooked number—the blood sugar level measured exactly one hour after drinking a glucose solution—may be one of the most powerful early warning signs we have.
This one‑hour glucose value comes from the oral glucose tolerance test, also called the OGTT. During this test, a person drinks a sugary solution, and doctors measure how the body handles it over time.
Most clinical guidelines focus on the fasting blood sugar level and the reading taken two hours after the drink. But the new study, published in the journal Metabolism, shows that the one‑hour result may reveal danger long before the other numbers rise.
Prediabetes is often seen as the stage between normal health and diabetes. But it is far from perfect as a warning system. Many people with prediabetes—over 40 percent—never develop type 2 diabetes.
And even more concerning, about 20 percent of people who later develop diabetes never showed signs of prediabetes at all. This means they missed the opportunity to take early action. Finding a clearer way to identify risk has become a major goal for researchers and doctors.
The research team studied the one‑hour plasma glucose value, often called 1h‑PG. International guidelines already suggest that a reading of 155 mg/dL or higher signals problems with how the body handles sugar.
What makes this number especially interesting is that it can rise long before fasting glucose or two‑hour glucose become abnormal. In other words, it may catch the earliest stage of the disorder, when the body is beginning to struggle but still has the ability to recover.
To test this theory, the team studied 317 adults in the Tübingen Lifestyle Intervention Program, also known as TULIP. These participants had different levels of glucose tolerance.
Some had normal results, some had high one‑hour glucose levels but normal other values, and some had classic prediabetes. The lifestyle program asked all participants to lose at least five percent of their body weight through better eating habits and regular physical activity.
Even before the intervention began, the people with high one‑hour glucose readings showed signs that their metabolism was beginning to weaken.
Their insulin sensitivity was lower, their beta‑cell function was reduced, and both liver fat and belly fat were higher compared with people who were completely healthy. But these values had not yet reached the level seen in prediabetes, meaning this stage might be the best time to intervene.
After nine months of lifestyle changes, the people with high one‑hour glucose levels showed remarkable improvement. Their insulin sensitivity and beta‑cell function recovered to levels seen in healthy individuals. Their liver fat decreased as well. While people with prediabetes also improved, their results were far less dramatic.
The long‑term findings were even more impressive. Over as many as twelve years of follow‑up, people with elevated one‑hour glucose levels who completed the lifestyle program were 80 percent less likely to develop type 2 diabetes than those with prediabetes.
Nearly half returned to completely normal blood sugar levels, which was twice the rate seen in the prediabetes group.
The researchers believe that the one‑hour value identifies a special “sweet spot” in early metabolic decline—a point where the body is under stress but still highly able to recover if given the right support. Weight loss, reduced liver fat, and improved insulin response all appear to help restore normal metabolism before the damage becomes too severe.
When reviewing and analyzing the findings, it becomes clear that the 1h‑PG measurement is a stronger predictor of future diabetes than many traditional markers, including fasting glucose, HbA1c, and the two‑hour OGTT reading. It highlights a stage where intervention is likely to be most effective.
This suggests that adding the one‑hour value to routine metabolic testing could help doctors identify at‑risk people much earlier and with far greater accuracy. The study’s strength lies in its long-term follow‑up, its careful grouping of participants, and the dramatic difference in outcomes between groups.
The research also suggests a shift in how we think about prevention. Instead of waiting for prediabetes to appear, doctors may eventually target the one‑hour reading as a trigger for action. If adopted into clinical practice, this could help millions of people take steps—through diet, exercise, and weight loss—that may prevent diabetes altogether.
If you care about diabetes, please read studies about Vitamin D and type 2 diabetes, and to people with diabetes, some fruits are better than others.
For more health information, please see recent studies that low calorie diets may help reverse diabetes, and 5 vitamins that may prevent complication in diabetes.
The study is published in Metabolism.
Copyright © 2025 Knowridge Science Report. All rights reserved.
