Diabetes in sport: how athletes can train and compete with the right treatment

The relationship between the athlete, diabetes and sport

Although diabetes is regarded as a disease of obese and the elderly, athletes can also suffer. But according to John Bye, the right management strategy can help diabetic athletes to continue to train and compete.

The incidence of diabetes is growing at a truly alarming rate. According to the latest statistics, there are over 14m diabetes sufferers in the US and more than 2m in the UK, figures that are expected to rise sharply over the coming years. The condition arises from an inability of the body to properly regulate levels of glucose in the blood either because of a lack of, or insensitivity to, the hormone insulin. And since insulin is the hormone that drives glucose into cells where it can be used for energy, this has profound consequences.

There are two types of diabetes; type 1 usually occurs during childhood and is caused by an autoimmune disorder where the immune system turns on and destroys the insulin producing cells of the pancreas. Type 2 (also known as adult onset) occurs later in life and although more complex in its aetiology, is thought to be caused primarily by reduced sensitivity of cells to insulin as a result of fat gain.

Symptoms of diabetes

The symptoms of diabetes include the following:

•    Unexplained tiredness;
•    Unexplained weight loss;
•    An increased thirst, which is difficult to quench;
•    Poor wound healing;
•    Increased urine production and more frequent trips to the loo;
•    Frequent fungal-type infections such as thrush;
•    Eye problems – eg blurring of vision

Many of these symptoms can easily be confused with overtraining; if there’s any doubt whatsoever, athletes and their coaches should seek the advice of a doctor sooner rather than later who will test blood glucose levels to confirm whether the diabetes is present. This is important because untreated diabetes can lead to numerous and potentially fatal complications such as an increased risk of stroke and heart attack, kidney failure, and nerve and blood vessel damage, leading to diabetic foot ulcers – a particular concern for diabetic athletes as even a poorly fitting shoe or piece of grit in the shoe can lead to an ulcer without the athlete being aware of the process. Untreated diabetic athletes are also prone to a number of musculoskeletal conditions, which can lead to poor joint mobility, pain and inflammation.


If diabetes has been diagnosed, some pre-exercise screening is advised before training is resumed or increased in order to check that the condition won’t be worsened by exercise. These tests include exercise stress tests to check out cardiovascular function, blood cholesterol, triglyceride and HBA1C (to check how well blood glucose has been controlled over recent months) tests, and urine/kidney function tests.

Drugs, exercise and diet in diabetes management

The successful management of diabetes entails keeping blood glucose concentrations in the physiological desirable range of 5-7mmol.l–1 (5-10mmol.l–1 following a meal) and therefore avoid the possible complications above. In mild diabetes, this may be possible by just paying careful attention to diet and exercise; in more severe cases, insulin (by tablet, injection or inhalation) may also be required. However, in all cases, successful diabetes management requires that the athlete develops a feel for how their body reacts to dietary, exercise or drug intervention so that they can adjust their management strategy to achieve the most stable blood glucose levels. This process takes time however and will almost certainly require input from the medical team to fine-tune things.

The impact of diet and exercise on the diabetic athlete can be summarised as follows:

•    Low-fat, high-carbohydrate diets are recommended (in line with general sports nutrition guidance!);
•    Slow releasing (low GI) carbohydrates are recommended in the 1-2 hour period before training/competition;
•    Blood glucose should be checked immediately before exercise; lower than 6.6mmol.l–1 indicates some extra carbohydrate should be consumed;
•    Carbohydrates should be consumed during prolonged exercise (30-60 grams per hour) and blood glucose levels monitored;
•    Those who use diabetic medication need access to carbohydrate-rich foods such as dried fruit, biscuits etc during exercise in case blood sugar levels drop unexpectedly;
•    Adequate fluid should be consumed to avoid dehydration;
•    Sustained aerobic exercise tends to decreases blood glucose levels, while anaerobic exercise increases blood glucose levels; athletes should therefore monitor their levels blood glucose levels during training to gain a feel for how each type training will affect them;
•    Athletes who consume a high-calorie diet to fuel heavy training, or for pre-competition carbohydrate loading) will almost certainly need some drug intervention in addition to diet/exercise to control their type 2 diabetes.
•    Athletes should also be aware that other environmental factors, such as tiredness, stress, viral infections etc can also affect how they react to exercise/diet/drugs and be prepared to adjust their management strategy accordingly.

Special considerations

Because insulin is currently banned by the World Anti-Doping Association (WADA), diabetic athletes need to obtain a Therapeutic Use Exemption (TUE) before they can compete legally (available from The TUE needs to be completed and signed by both the athlete and the doctor, and then returned to the relevant governing body. Diabetic athletes who travel abroad must have with them a copy of their doctor’s prescription so they can carry needles, syringes and blood glucose monitoring devices. They should also remember that travelling across time zones will almost certainly affect blood glucose, so they may need to adjust their management strategy accordingly. It’s also a good idea to carry a MedicAlert® Bracelet or similar so that in the case of illness, others are aware of their condition.

Original article by John Bye; summary by Andrew Hamilton 

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