Managing diabetes is a matter of balance, and eating and exercise are two of the most important factors in the project. Medication also affects the balance of calories consumed and calories burned. Pharmacists writing for the American Diabetes Association recommend waiting at least an hour after eating even a small snack before you exercise, and carefully monitoring your blood sugar before, during and after any workout. The challenge is greatest for insulin-dependent Type 1 diabetics.
Gentle and Brief
In 2004, the National Diabetes Education Program of the National Institutes of Health published guidelines for school nurses helping young diabetics manage their blood sugar levels. Even brief, light exercise such as walking 1/2 mile or stretching for 30 minutes was recommended only when a blood sugar was monitored at more than 100 mg/dL. At a lower reading, the guidelines recommend eating an additional 10 to 15 g of carbohydrate, such as a packet of two saltines.
Moderate Exercise
Exercises such as swimming or jogging at a moderate pace, playing tennis or dancing are considered safe to start at a glucose reading of 180 to 350 mg/dL. MayoClinic.com recommendations are more cautious over all levels of exercise: It cuts off "good to go" at 250 mg/dL and set 250 to 300 mg/dL as a "caution zone." The school nurses were advised to administer that snack between 100 and 180 mg/dL, and below 100 to give double the snack before moderate exercise, plus a small snack every hour during the activity.
Strenuous Exercise
Full-out sports play, such as football, soccer, hockey or basketball makes it difficult to keep blood sugar under control, since even with readings in the safety zone of 180 to 350 mg/dL these athletes may need to add carbohydrates every hour. They may need a boost as big as 50 g to get started from a blood-sugar reading in the "normal" range below 100 mg/dL.
Unsafe at Any Speed
Exercise may seem like a good way to bring down a high blood-sugar reading, but all the experts caution that a reading of 350 mg/dL or more may indicate that your body lacks the insulin, or is unable to use it, to fuel your muscles with circulating sugar. Instead, you may be breaking down body fat, which produces ketones, and at high levels they can be deadly. If your blood sugar is this high, do not attempt to exercise until you've tested your urine for spilled ketones. Even moderate exercise can turn a moderate level of ketones into ketoacidosis and coma.
Dynamics
Exercise at any level will affect your blood-sugar reading, and what's most important may be knowing whether your levels are rising or falling as your dinner is metabolized. The ADA therefore recommends testing 30 minutes before you start out on your walk and again just before you start. If your blood sugar was in a safe zone and has fallen already, stay home and enjoy a piece of fruit to give you fuel for your venture. If you're going to exercise for more than 30 minutes, check your blood sugar while you're at it to make sure you're maintaining good balance.
