Prevent a slightly high blood sugar from progressing to diabetes

Prevent a slightly high blood sugar from progressing to diabetes

The Medicine Cabinet: Ask the Harvard Experts

By Howard LeWine, M.D.

Q: I recently had a blood sugar test. The level was slightly higher than normal. Does this mean I have diabetes?

A: No, it more likely means you have prediabetes. It’s a condition in which the blood sugar is higher than normal, but not yet high enough to be considered type 2 diabetes. Prediabetes can go on for years, and can even progress to full-blown diabetes, without causing a single symptom.

The most common way to test blood sugar levels is a fasting blood sugar test. It requires a single blood sample that’s collected after you’ve fasted for at least eight hours.

Normal blood sugar is less than 100 milligrams per deciliter of blood (mg/dL) after an eight-hour fast. You have diabetes if your blood sugar is 126 mg/dL or higher after a fast. People with a blood sugar reading of above 100 but below 126 have prediabetes.

A different blood sugar test called hemoglobin A1c (HbA1c) can be done without fasting. It reflects your average blood sugar over the prior two to three months.

A normal HbA1c is 5.6 percent or lower. A level of 6.5 percent or higher means you have diabetes. And prediabetes is defined by an HbA1c between 5.7 percent and 6.4 percent.

While having prediabetes definitely increases your risk, it doesn’t mean you’ll definitely get diabetes. Once you know that you have prediabetes, you can take steps to prevent it from developing into full-blown type 2 diabetes. A few simple lifestyle changes can stop you from ever getting a diabetes diagnosis.

Certain foods or eating patterns might be particularly helpful for preventing diabetes. For example, people who eat a Mediterranean style diet have a lower incidence of type 2 diabetes. The diet is high in whole grains, whole fruits (not fruit juice), vegetables and fish.

Combine diet with at least 150 minutes of exercise a week. Taking a brisk walk for 30 minutes a day is a good option–or you can choose another aerobic activity, such as dancing or playing tennis.

If you’re overweight, trimming down by even a small amount can help you avoid diabetes. Losing just 5 percent to 7 percent of your body weight is enough to reduce your risk. If you weigh 165 pounds, you can make a difference with a loss of just 8 to 12 pounds.

These three changes — diet, exercise and weight loss — can cut your risk of getting type 2 diabetes by more than half.

(Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit