When is the Best Time to Test Blood Sugar?

Patient Expert
Medically Reviewed
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The preferred time to test blood sugar isn't before breakfast any more. Researchers looking at studies of hundreds of people with type 2 diabetes suggest that high blood glucose levels after meals has a greater effect on A1C levels among people who have their diabetes under good control than among those with poor control.

When A1C results are low - less than 7.3 percent - mealtime glucose contributes about 70 percent of the A1C. However, when A1C results are high - greater than 10.2 percent - fasting blood glucose contributes 70 percent of the A1C value.

If your A1C levels are above 7.0 percent, you run a much greater risk of complications. That means getting your diabetes under control needs to be your top priority. After you do that, you can concentrate on testing after meals.

But do we start counting from the beginning, the middle, or the end of the meal? And should we test one, two, or more hours after eating?

There is a great variation in the length of a meal. So it is more precise to start counting from the time of the first bite. Another reason to start counting from the beginning of a meal is because our glucose levels begin to rise about 10 minutes after the start of a meal.

Both organizations recommend that most of us test two hours after eating. While your blood glucose level could be highest one hour after a meal, there are good reasons to wait until two hours after the first bite. Writing on a diabetes mailing list, someone called Helen said it best:

"If I aim for pre-meal levels to occur an hour after eating, I chance going low after two hours and for sure after three hours. My blood glucose level tends to decline from hour two to hour three. Therefore I do not test one hour after - there is nothing I would do with that information other than aggravate myself."

The exception, according to the ADA, is women who have diabetes and are pregnant. They could benefit more from testing one hour after eating.

The point of testing is to help you bring your levels down. Talk with you doctor about how often you should be testing your blood glucose to avoid overuse.

Several different organizations have set targets for blood glucose levels two hours after a meal. The ADA has the easiest target, less than 180 mg/dl (10 mmol/l). The International Diabetes Federation and the World Health Organization recommend a target of less than 160 mg/ dl (8.9 mmol/l). The American Association of Diabetes Educators, the AACE and the American College of Endocrinology have the most aggressive targets, under 140 mg/dl (7.8 mmol/l). Whatever target you accept, you might bear in mind that people who don't have diabetes seldom have a level of more than 130 mg/dl two hours after a meal. If you check your level after each meal, you will be able to have a lower blood glucose level, a lower A1C, and less chance of complications.