Sugar Highs Explained

By John J. "Jack" Merendino Jr., MD, Best Life Chief Medical Advisor, endocrinologist and co-author, along with Bob Greene and Janis Jibrin, MS, RD, of The Best Life Guide to Managing Diabetes and Pre-Diabetes.

Posted on | By John J. "Jack" Merendino Jr., MD

You're taking your medications as prescribed and you're keeping an eye on your carbohydrates, yet there still may be times when your blood sugar is too high.  There are many reasons for blood sugar surges--I'd like to zero in on two common issues: high morning sugar and sugar that's high after exercising. 

Waking up to high sugar

You'd think that your blood sugar should be lower after a night's sleep. After all, you haven't eaten anything for many hours. But the body needs glucose 24 hours a day, and if you're not getting it from food, your body will turn to stored glucose in the liver. Your pancreas needs to make insulin to deal with this glucose, just as it does for glucose derived from the food you eat. Unfortunately, in many people with diabetes, insulin production during periods of fasting is as meager as (or worse than) during eating. Therefore, the sugar may rise overnight because glucose being produced by the liver is not matched by adequate insulin from the pancreas. Also, certain medications, including glyburide (brand name Micronase or DiaBeta), glipizide (brand name Glipizide) and glimepiride (brand name Amaryl), improve meal-related insulin production more than fasting insulin production. As a result, many people who take these medicines have higher glucose levels in the morning than before bed at night.

Sometimes a bedtime snack will actually help lower morning blood glucose, because the sugar (from the carbohydrates in your snack) that hits your bloodstream causes the body to release more insulin than the sugar your liver releases during the night while you're fasting.  Ideally, your snack should contain protein, some healthy fat and a slowly absorbed carbohydrate, such as two teaspoons of peanut butter on a half-slice of stone-ground whole-wheat bread. If this doesn't work, using a long-acting form of insulin as part of the treatment is usually very effective.

Your Exercise High

My patients who come to me complaining of high blood sugar after exercise are bewildered and even depressed--"Isn't exercise supposed to be helping me lower my blood sugar?  Can't I catch a break?" 

My advice to them usually is:

  1. Continue exercising.
  2. Don't be discouraged!

Exercise is virtually always helpful in managing diabetes, unless you are exercising in a way that is going to hurt you or you have some reason, such as untreated heart disease, that makes it dangerous to exercise. (Always check with your doctor before you begin an exercise program, and start at a comfortable level of exertion, working your way up at a safe pace.)

Although you'd expect exercise to help reduce blood sugar, its effect in the short term can be unpredictable. Your blood glucose is probably going up because of your epinephrine (also called adrenaline) output during exercise. Your adrenal glands manufacture epinephrine during exercise; the more vigorous the exercise, the greater the epinephrine production will be. Epinephrine causes an increase in heart rate, more forceful contraction of the heart muscle and better oxygen delivery from your lungs, all of which allow you to exercise more intensely. It also causes the release of glucose from your liver and the breakdown of glycogen into glucose inside your muscle cells. This is necessary to provide fuel for your workout. In some people, this results in higher glucose levels for up to several hours after exercise--but after this period has elapsed, the glucose tends to fall to lower levels than it would have without the exercise. In addition, the increased muscle mass you put on will help burn more glucose at rest, improving glucose control between bouts of exercise. A few extra bonuses: Strength training will keep your bones strong, improved cardiovascular fitness will cut your risk of heart disease, and increased physical activity will elevate your mood--all excellent reasons to keep exercising.

From TheBestLife.com, used with permission.

Article written by John J. "Jack" Merendino Jr., MD
Best Life Chief Medical Advisor, endocrinologist and co-author, along with Bob Greene and Janis Jibrin, MS, RD, of The Best Life...