Exercise & Hypoglycemia
By Sheri Colberg, PhD, FACSM, author, professor, exercise physiologist, and member of the Perrigo Diabetes Care advisory board, and Riva Greenberg, diabetes patient-expert, author, speaker, and Huffington Post columnist.
Exercise presents its own special challenges for managing blood sugar. Since any activity increases your body's use of blood sugar, hypoglycemia can develop during or following exercise. However, the rewards of exercise — including overall fitness, weight control, stress release, and better blood sugars up to 48 hours after you exercise — make it well worthwhile.
The more you understand about what makes your blood sugars go down (or sometimes up) during exercise, the easier it becomes to manage and the more confident you can be about doing activities and staying in control of your diabetes.
Much of your blood sugar response has to do with how much insulin is in your bloodstream, along with how well that insulin is working. If your insulin levels are high during an activity, your muscles will use more blood glucose and you're more likely to end up with low blood sugar. You can even experience hypoglycemia up to 48 hours after you exercise.
You can prevent lows while making exercise a regular part of your life. Here's how:
- Learn how your body responds to exercise by checking your blood sugar levels before, (occasionally) during, and after exercise.
- If your blood sugar is near or below 70 mg/dl (3.9 mmol/l) before you exercise, bring it back within normal range before you begin. Make sure you know how to treat a low before you begin.
- Always be prepared to correct a low by having a glucose product with you during exercise. Don't assume you'll be able to find pure glucose, soda, juice, or candy nearby if you need it when you're exercising.
- If you exercise long and hard, your body will use a lot of carbohydrate, so you'll likely need to eat some carbs both before and during the activity to prevent early fatigue and hypoglycemia.
- Whenever exercising for an hour or more, check your blood sugar every 30 minutes or so to catch lows early.
- If you begin to feel your blood sugar dropping and are able, sprint as hard as you can for 10 to 30 seconds. Your body will release glucose-raising hormones. (This may be enough to keep your blood sugar level for a short while. However, if you're going to be active longer, you may also need to consume some glucose.) Pick a good time of day to exercise. You are less likely to develop hypoglycemia when you exercise moderately in the morning before breakfast because that is when your body is most insulin resistant.
- If your blood sugar is lower for several hours after activity, you may need to take less medication (typically rapid-acting insulin) than usual during that time.
How to correct an exercise-related low
If your blood sugar is below 70 mg/dl:
Step 1: Stop exercising immediately and eat 15-20 grams of pure glucose or another food containing fast-acting carbohydrate.
Glucose tablets, liquids, or gels are the preferred carbohydrate to correct low blood sugar. If you do not have a glucose product, consume another fast-acting carbohydrate such as half a glass of fruit juice or soda with sugar (not diet), 4-7 hard candies, or a glass of low or fat free milk.
Step 2: Wait 15 minutes, and then check your blood sugar again.
If your blood sugar is still below 100 mg/dl (5.5 mmol/l), or your goal range, correct again with another 15-20 grams of fast-acting carbohydrate. Do not restart your exercise until your blood sugar is above 100 mg/dl or in your target range.
Intense workouts may raise your blood sugar.
Immediately after intense exercise, you may experience high blood sugar for a few hours. This is because intense exercise causes your body to release glucose-raising hormones, such as adrenaline. Your body may need more insulin to bring your blood sugar levels back to normal.
If you only take oral medications, try doing 10-15 minutes of moderate exercise after an intense workout to help lower blood sugar. Also, keep a close eye on your blood sugar for 24 to 48 hours after intense activity. After the initial high blood sugar, your blood sugar may drop as your body works to restore the glucose in your muscles that was depleted during your activity.
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NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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