Exercise has numerous benefits for people with diabetes, but it must be approached with consideration for your blood sugar levels. This is because exercising can lead to hypoglycemia or dehydration if you are on medications that increase the insulin levels in your body, or ketoacidosis if you have type 1 diabetes.
However, almost all patients with diabetes can benefit from some form and level of physical activity. For people with type 2 diabetes that is weight-related, exercise helps to maintain a healthy weight and reduce the risk for heart disease. Exercise can also promote better blood sugar control and encourage better blood flow.
Motivation and concern for your blood sugar levels can be a deterrent to exercise, but don’t give up. You can find an exercise program that works for you. Your physician can help you determine appropriate activities and intensities, as well as help you decide on safe blood sugar levels before exercising to allow you to get and stay fit safely.
If you have not exercised in some time and fall in one or more of the following categories, see your physician before beginning exercise:
- 35 years or older
- history of diabetic neuropathy
- history of heart disease
- history of peripheral vascular disease
- lived with diabetes for more than 10 years
Your physician may recommend an exercise stress test prior to beginning an exercise program. This test is usually recommended for people who match one or more of the following criteria:
- over 30 years of age
- living with type 1 or type 2 diabetes for over 10 years
- cigarette smoker
- proliferative or preproliferative retinopathy
- nephropathy, including microalbuminuria
- advanced nephropathy with renal failure
- autonomic neuropathy
- cigarette smoker
This will ensure your heart is in good enough shape for you to safely exercise.
When you exercise and have diabetes, it's important to be prepared. You should always wear a medical alert bracelet or other identification that lets people know you have diabetes. This also includes having items on-hand that can help to raise your blood sugar if you are on medications that increase insulin levels in case of low blood sugar. Examples include:
- fast-acting carbohydrates such as gels or fruit
- glucose tablets
- sports drinks that contain sugar, such as Gatorade or Powerade
While you should always drink plenty of fluids when working out, people with diabetes should be especially careful to take in enough fluids. Dehydration during exercise can adversely affect your blood sugar levels. Take care to drink at least 8 ounces of water before, during, and after your exercise session to stay hydrated.
When you exercise, your body starts to use blood sugar as an energy source while also becoming more sensitive to insulin in your system. These two effects can mean your blood sugar can drop to low levels while you exercise if you are on medications that increase insulin production in the body. For this reason, it's important to monitor your blood sugar before and after you exercise if you are on these medications. Consult your physician for ideal levels.
Exercising outdoors can also affect your body's response to insulin. For example, extreme fluctuations in temperature while exercising can affect your blood sugar levels.
What happens if your blood sugar is too low or high before you intend to exercise? If blood sugar levels are high, you can test for ketones, and avoid exercise if you are positive for ketones. If your levels are low, you should eat something before you start exercise. Speak with your health care team to create a plan that works for you.
Some people with diabetes may need to avoid strenuous exercise. This is true if you have some forms of diabetic retinopathy, eye disease,high blood pressure, or foot concerns. Strenuous exercise may also increase your risk of low blood sugar many hours after exercise, so people who are on medications that put them at risk for low blood sugar should be careful to test blood sugars longer after strenuous exercise. Always talk with your physician about the best approach to take given your unique health concerns.
You should check your blood sugar about 30 minutes prior to exercising to ensure your blood sugar level is healthy enough for you to begin exercising. While your physician may set individual goals with you, some general guidelines from The Mayo Clinic include:
Less than 100 mg/dL (5.6 mmol/L): Refrain from exercising until you have eaten a high-carbohydrate snack. This includes fruit, half a turkey sandwich, or crackers. You may wish to re-check your blood sugar before exercise to ensure it is in the proper ranges.
Between 100 and 250 mg/dL (5.6 to 13.9 mmol/L): This blood sugar range is an acceptable one for when you begin exercising.
250 mg/dL (13.9 mmol/L) or higher: This blood sugar level may indicate the presence of ketones. This means your body does not have enough insulin to support your current blood glucose levels. You typically can test your urine for the presence of ketones. If they are present, refrain from exercising until your blood sugar levels have decreased.
300 mg/dL (16.7 mmol/L) or higher: This indicates hyperglycemia, which can be worsened by exercise in people with type 1 diabetes who are insulin-deficient and ketotic. People with type 2 diabetes rarely develop such a profound insulin deficiency, and do not usually need to postpone exercise because of high blood glucose, so long as they are feeling well and remember to stay hydrated .
Recognizing hypoglycemia during exercise can be difficult because exercise by nature puts stress on your body. You can also experience unique symptoms, such as unusual visual changes, when your blood sugar gets low that you may not have with traditional hypoglycemia.
Examples of exercise-induced hypoglycemia symptoms in those with diabetes include:
- sudden onset of fatigue
- sweating excessively
- tingling in your hands and/or tongue
- trembling or shaky hands
If these symptoms happen to you, rest and eat or drink a fast-acting carbohydrate-containing food to help bring your blood sugar levels back up.
The American Academy of Family Physicians recommends consulting with your physician when determining the best exercise type for you given your overall current state of health. A good place to start is some form of mild aerobic exercise, which challenges your lungs and heart to strengthen them. Some examples could be walking, dancing, jogging or taking an aerobics class.
However, if you have experienced damage to your feet due to diabetic neuropathy, you may wish to consider exercises that keep you off your feet, preventing numbness and tingling. These could include riding a bicycle, rowing or swimming. Always wear comfortable, well-fitting shoes coupled with breathable cotton socks, such as cotton, to avoid irritation.
Do not feel as if you have to be a marathon runner with your first try. Instead, try starting with aerobic exercise in increments of 5 to 10 minutes, then working your way up to about 30 minutes of exercise most days of the week.