Diabetes and Exercise

Diabetes mellitus is a common, chronic disease, in which the pancreas is unable to adequately control blood glucose (sugar) levels. There are 2 types of diabetes. Type 1 diabetes patients are unable to produce insulin, a hormone that causes sugar in the blood to be stored in the body. People with type 1 diabetes may compensate by giving themselves injections of insulin. Type 2 diabetes involves not producing adequate amounts of insulin to control blood glucose levels. People with type 2 diabetes control their blood glucose by monitoring their food intake or by taking medicine. Exercise is an important part of diabetes treatment. During exercise, the muscles use a greater amount of glucose from the blood for energy. This lowers your blood glucose, which is the same effect you would get from taking insulin. It has been shown that endurance athletes are more sensitive to insulin than inactive people.


Many people with a mild case of diabetes have no symptoms. However, if left uncontrolled, diabetes can lead to several complications that could be prevented with treatment of the disease.

General symptoms of diabetes include:

  • Frequent urination (polyuria).

  • Frequent thirst and drinking (polydipsia).

  • Increased food consumption (polyphagia).

  • Fatigue.

  • Poor exercise performance.

  • Blurred vision.

  • Inflammation of the vagina (vaginitis) caused by fungal infections.

  • Skin infections (uncommon).

  • Numbness in the feet,caused by nerve injury.

  • Kidney disease.


The cause of most cases of diabetes is unknown. In children, diabetes is often due to an autoimmune response to the cells in the pancreas that make insulin. It is also linked with other diseases, such as cystic fibrosis. Diabetes may have a genetic link.


  • Athletes should strive to begin exercise with blood glucose in a well-controlled state.

  • Feet should always be kept clean and dry.

  • Activities in which low blood sugar levels cannot be treated easily (scuba diving, rock climbing, swimming) should be avoided.

  • Anticipate alterations in diet or training to avoid low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia).

  • Athletes should try to increase sugar consumption after strenuous exercise to avoid hypoglycemia.

  • Short-acting insulin should not be injected into an actively exercising muscle. The athlete should rest the injection site for about 1 hour after exercise.

  • Patients with diabetes should get routine checkups of the feet to prevent complications.


Exercise provides many benefits to the person with diabetes:

  • Reduced body fat.

  • Lower blood pressure.

  • Often, reduced need for medicines.

  • Improved exercise tolerance.

  • Lower insulin levels.

  • Weight loss.

  • Improved lipid profile (decreased cholesterol and low-density lipoproteins).


If performed incorrectly, exercise can result in complications of diabetes:

  • Poor control of blood sugar, when exercise is performed at the wrong time.

  • Increase in renal disease, from loss of body fluids (dehydration).

  • Increased risk of nerve injury (neuropathy) when performing exercises that increase foot injury.

  • Increased risk of eye problems when performingactivities that involve breath holding or lowering or jarring the head.

  • Increased risk of sudden death from exercise in patients with heart disease.

  • Worsening of hypertension with heavy lifting (more than 10 lb/4.5 kg). Altered blood glucose and insulin dose as a result of mild illness that produces loss of appetite.

  • Altered uptake of insulin after injection when insulin injection site is changed.

NOTE: Exercise can lower blood glucose effectively, but the effects are short-lasting (no more than a couple of days). Exercise has been shown to improve your sensitivity to insulin. This may alter how your body responds to a given dose of injected insulin. It is important for every patient with diabetes to know how his or her body may react to exercise, and to adjust insulin dosages accordingly.


  • Eat about 1 to 3 hours before exercise.

  • Check blood glucose immediately before and after exercise.

  • Stop exercise if blood glucose is more than 250 mg/dL.

  • Stop exercise if blood glucose is less than 100 mg/dL.

  • Do not exercise within 1 hour of an insulin injection.

  • Be prepared to treat low blood glucose while exercising. Keep some sugar product with you, such as a candy bar.

  • For prolonged exercise, use a sports drink to maintain your glucose level.

  • Replace used up glucose in the body after exercise.

  • Consume fluids during and after exercise to avoid dehydration.


  • You have vision changes after a run.

  • You notice a loss of sensation in your feet after exercise.

  • You have increased numbness, tingling, or pins and needles sensations after exercise.

  • You have chest pain during or after exercise.

  • You have a fast, irregular heartbeat (palpitations) during or after exercise.

  • Your exercise tolerance gets worse.

  • You have fainting or dizzy spells for brief periods during or after exercise.