Low Blood Sugar During Exercise?

Q:       I’ve recently started on insulin to help manage my diabetes. Should I be concerned about low blood sugar during exercise? What do you recommend to monitor blood sugar and avoid dips during a workout?
 A: Managing blood sugar can be very difficult during exercise, especially for someone using medication like insulin to treat diabetes. Exercise naturally lowers blood sugar because sugar behaves as fuel for contracting muscles. Normally, this is a good process and is why exercise may prevent diabetes and obesity. (Diabetes is defined as higher-than-normal sugars in the bloodstream.) However, for people who are taking insulin or oral hypoglycemic medications, exercise can cause too low of blood sugar and lead to symptoms that make exercise very uncomfortable and even dangerous.
In fact, the major adverse effect of insulin therapy is hypoglycemia, or low blood sugar. Almost every patient who takes insulin will, indeed, experience hypoglycemia at some point. In my practice, when a patient is started on insulin, he or she is informed of the risk of hypoglycemia and the associated symptoms, which can include nervousness, sweating, shaking, hunger, or even losing consciousness or seizures. The patients are also shown how to prevent and treat hypoglycemia on their own. This may involve eating on schedule, checking blood sugars, or wearing a continuous glucose monitor (CGM). Someone on insulin who is at high risk of hypoglycemia should wear or carry diabetes identification.
It’s important to take your medication into account when exercising. During exercise, muscle tissues extract sugar out of the blood and transfer those sugars into muscle cells for use. This sugar-lowering process is a benefit of exercise, and the body has adaptations to prevent sugar levels from going too low in the blood. However, insulin or oral hypoglycemic medications, which also work to lower blood sugar, may be too powerful during exercise. These medications override the normal regulatory systems that prevent hypoglycemia, and as a result, the patient may experience low blood sugars with exercise.
But that doesn’t mean you should shy away from exercise.
The best advice for patients who take insulin and participate in physical activities is to carefully keep track of their blood sugars. The usual recommendation is that sugars should be between about 120 and 180 mg/dl before exercise. By looking for patterns of when sugars go up and down throughout the day, you can adjust your routine accordingly. For example, if you exercise in the afternoon, but usually have higher blood sugars at that time, it may be safe to exercise without making any changes. If your blood sugar is too high, you may also need to drink more water and perhaps take a correction dose of insulin. On the other hand, if your sugar is usually low at that time, you may need to reduce your insulin dose or eat something before exercising.
A snack that contains carbs, protein, and fiber — such as a cracker with peanut butter, nuts, or a small protein bar — could slowly correct the sugar to a safe level. Drinking a sugary beverage or sports drink is not recommended because that will raise the sugar too high.
For someone on insulin injections multiple times daily, an insulin pump device may be useful to prevent fluctuations in sugar with exercise, as often the problem involves the long-acting insulin, which cannot be adjusted after taking the daily dose.
It is crucial to talk to your healthcare provider before initiating an exercise program or making any adjustments to your treatment plan. As diabetes often poses cardiovascular risk, please clear the activity with your doctor and stratify risk. In addition, review your blood sugars with your doctor to determine an appropriate insulin regimen for days that you exercise, which may differ from the days you do not exercise.