Blood Sugar Monitoring: When to Check and Why

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Blood Sugar Monitoring: When to Check and Why

Checking before meals

Similar to fasting readings, monitoring your blood sugar before meals gives you a baseline reading of your blood sugar before you eat. Some medical professionals call these preprandial readings.

“This is the best time to check your blood sugar, so you know what it is before you start the meal,” says Ananda Basu, MD, associate professor and consultant in the Division of Endocrinology at the Mayo Clinic in Rochester, Minnesota. “Once you eat, your blood sugar is going to go up, but the baseline should be back to normal by the next meal.”

If your premeal readings are in the recommended range and your HbA1c test results are also in your target range, Dr. Basu says that monitoring after meals is not necessary. One reason is that blood sugar meters are most accurate when blood sugar levels are between 80 and 140 mg/dl, and after-meal spikes can exceed those levels. (For information about getting the most accurate readings from your blood sugar meter, check out “Getting Accurate Readings.” And to learn about using alternate sites to monitor, see “When Your Fingers Have Had Enough.”)

“We don’t have any hard data from clinical studies showing the long-term effects of postmeal readings,” he adds. “We know that most people spike, but we don’t know if people who spike more have more complications or those who spike less have fewer complications. Until more data prove that postmeal values are important, I find it hard to recommend postmeal monitoring.”


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