RECOMMENDATIONS FOR EXERCISE IN TYPE 1
If you have type 1 diabetes, consider taking the following
Keep an Exercise Log
Write down when you are exercising, the relation to the previous meal and
insulin bolus, the type of exercise, the duration and intensity, how much carbohydrate (CHO) was consumed
before, during, and after exercise, and blood glucose levels (see Figure 9-2). This information is essential for
making appropriate changes the next time you exercise.
Plan Your Exercise
Plan how long you will exercise, how intense it will be, and how soon after a meal you will
exercise. Try to be consistent from day to day.
Monitor Blood Glucose Levels
Take your glucose meter with you when you exercise, and check your blood glucose levels
before, during (at least once or twice), and after exercise. If possible check them at least two or three times
at half-hour intervals before the exercise to ﬁnd out the direction of glucose changes. Prick your ﬁnger for the
blood sample—do not use your forearm, because there may be a ﬁve- to twenty-minute lag in the glucose response
in the arm.
With intense exercise, be prepared for lower glucose levels several hours after exercise, for
example, in the middle of the night. Have a bedtime snack, or wake up and check your blood
Adjust the Insulin Dose
Before exercise, adjust the bolus or basal insulin, or both, in anticipation of the
A bolus of a
fast-acting insulin analog lasts for about four hours, and the peak is at about one to one and a half
hours. If you exercise within two hours, you will need to cut back on the premeal bolus (to 50 to 75
percent of your usual dose).
adjustment in basal insulin dosing is easier if you are on an insulin pump. If you are planning for
exercise of long duration (longer than ninety minutes), you may want to cut back the amount of your
basal insulin for up to two hours before the exercise. If you are participating
in competitive sports, you may ﬁnd that the “adrenaline rush”
means that you may have to increase your basal insulin temporarily for up to two hours before the
Adjusting the basal dosage of the
long-acting insulins like glargine or detemir is trickier—you can try cutting back to 50 to 80 percent
of the dose on the days you exercise. Any high glucose levels earlier in the day can be covered by
giving additional bolus insulin.
During exercise your options will depend whether you are on a pump or on
If you are on
the pump, you have a number of options as to what to do regarding the basal insulin delivery. For
short-duration exercise lasting an hour or so, you can simply come off the pump. If the pump is taken
off for more than an hour (for example, while swimming), a small bolus may be given before coming off.
If you will be exercising for several hours, a temporary basal amount (20 to 75 percent of your usual
dose) might be necessary. For example, if you go cross-country skiing for several hours, you may change
your basal to 20 to 50 percent of your usual dose for the duration of the exercise. A similar change
may be required for a marathon.
If you are on
insulin glargine or detemir, you do not have the option of changing the basal rate during exercise:
your only option is to consume additional carbohydrates.
After exercise you will adjust
the bolus and basal insulins for the acute effects of exercise and also for the effects of chronic
If you get
predictably high glucose levels after exercise, be prepared to give a little bolus of a fast-acting
insulin analog. With intense and/ or prolonged exercise, hypoglycemia can occur several hours (up to
twelve to sixteen hours) afterward, and you should be prepared to reduce the basal insulin (or eat a
snack). You might consider purchasing a continuous glucose monitoring system that can alert you to
weekend of increased physical activity such as skiing, a reduction in insulin requirements may persist
for an additional twenty-four hours.
training, you may become more insulin sensitive, and you may need to change your usual insulin regimen
by cutting back on both basal and bolus insulin doses.
For athletes with diabetes, it is recommended that 55 to 60 percent of the total daily
kilocalories should be carbohydrates. Endurance athletes (such as long-distance runners or cyclists) should
consider eating a carbohydrate-rich meal (1 to 2 grams of carbohydrate per kilogram of body weight) about three
to four hours before exercising to maximize pre-exercise glycogen stores. If the exercise is unplanned, eat 20
to 30 grams of carbohydrate immediately before you exercise.
The amount of carbohydrate that needs to be consumed will depend on the duration and
intensity of the exercise. Generally speaking, about 20 to 30 grams of carbohydrate is needed for each thirty
minutes of exercise. Table 9-1 provides a good starting point in determining how many grams of carbohydrate you
might need every half hour for different types of exercise.
The type of carbohydrate you consume can vary:
exercise, you could have fruit (apples, dried apricots), bread, yogurt, porridge, pasta, or
exercise, you could have a fruit juice/water mixture or sports drink. Sports drinks can give you some
sodium and potassium as well as carbohydrate. Read the labels for the carbohydrate, sodium, and
potassium contents. Sport gels or carbohydrate-rich bars are also good
sources of rapidly absorbed carbohydrates and salts—usually, you want to drink some water with
After exercise, you can have
bread, potato, rice, cereal such as cornﬂ akes, a granola bar, or
Dehydration will increase your glucose levels, so you need to drink plenty of ﬂ uids while
exercising. In the two hours before exercise, drink two glasses of water, and during exercise, drink enough to
replace ﬂuid loss. For prolonged exercise such as running or cycling, drinking approximately 250 ml (8 ounces)
every twenty minutes of exercise would be reasonable. Sport drinks are good for ﬂuid and carbohydrate
replacement. Avoid drinking too much ﬂuid, because this can lead to low sodium levels.
Provide Emergency Information
Wear your MedicAlert bracelet or shoe tags, just in case you get a severe episode of