Association of Diabetes Care and Education Specialists

Association of Diabetes Care and Education Specialists

August 10, 2019
4 min read

Managing glucose levels requires planning, medication adjustments before and after exercise

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HOUSTON — Paying attention to timing and making careful adjustments to insulin are critical aspects of maintaining optimal glucose levels and achieving better insulin sensitivity during and after exercise, according to findings presented at the American Association of Diabetes Educators annual meeting.

Gary Scheiner

“Physical activity is the most powerful tool we have for improving insulin sensitivity. It’s more powerful than any medication combination that’s available,” Gary Scheiner, MS, CDE, owner and clinical director of Integrated Diabetes Services in Wynnewood, Pennsylvania, told Endocrine Today. “So, somebody who wants to improve their glucose control and stay below renal threshold within a healthy range, physical activity is an extremely powerful mechanism for accomplishing that.”

When it comes to the relationship between exercise and glycemic management, Scheiner said it is bidirectional, with exercise yielding benefits for glycemic management and lowering potential spikes in blood glucose, especially after eating. Meanwhile, when glucose levels are optimized, individuals can experience boosts to strength, stamina, speed, flexibility and reaction times. However, uncontrolled blood glucose levels, Scheiner said, can lead to dehydration, poor quality sleep and deterioration of neuromuscular transmission, muscular contractility, mental sharpness and flexibility.

Dealing with hypoglycemia

Hypoglycemia during and after exercise is a risk for anyone with diabetes but can be avoided with planning, according Scheiner. The danger is particularly relevant for those taking insulin, sulfonylureas or meglitinides, he said.

“For those who take insulin secretagogues, it’s usually better to exercise after a meal in cases like that or to reduce the dose of oral medicine that they’re taking,” Scheiner said. “If they’re exercising regularly, or even semiregularly, they should have a discussion with their physician about alternative medications. We have such better medications on the market now with fewer side effects.”

Hypoglycemia due to physical activity is also more likely to occur for those using premixed insulin, multiple daily injections, insulin pumps or basal insulin, which means more carefully calibrated utilization of these treatments is needed.

“For patients who take meal-time insulin, they’re either going to need to reduce the insulin dose for post-meal activity or consume extra carbohydrates for pre-meal activity because they still have basal insulin in their system,” Scheiner said, while noting that adjusting basal doses is more effective in combination with longer periods of exercise.

Exercise equipment 2019 
Paying attention to timing and making careful adjustments to insulin are critical aspects of maintaining optimal glucose levels and achieving better insulin sensitivity during and after exercise.
Source: Adobe Stock

Those using insulin pumps should decide before exercising whether to remain connected. Although strategies exist for avoiding disconnection during exercise, such as applying to less exposed parts of the body, opting to remove the pump can still be a safe decision with planning.

“At minimum, they should give themselves a bolus immediately before disconnecting to replace the next couple of hours of basal they’re going to miss, and then when they reconnect, as long as glucose is not low or falling quickly, they should give themselves a small bolus,” Scheiner said. “You have to look at the timing of the activity and also what a person’s typical active insulin duration is. Someone whose insulin clears very quickly is at greater risk of insulin depletion than somebody whose insulin takes a long time to clear.”

Hypoglycemia does not always occur during exercise or even immediately after. More than a day can pass before this “delayed-onset hypoglycemia” is noticeable, but to prevent such an event, Scheiner recommends basal insulin reductions, the consumption of slow-acting carbohydrates and more regular blood glucose checks for several hours after exercising.

Avoiding hyperglycemia

Hyperglycemia is also a risk before, during and after exercise. Scheiner said that due to rising adrenaline levels during exercise, there is a natural tendency for individuals to experience higher glucose levels. This is particularly true for activities such as baseball and golf, in which there are short bursts of high-intensity activity followed by long periods of rest.

“If you plan ahead, if you know what to expect, you can compensate for those kinds of things,” Scheiner said. “You can use rapid-acting insulin to prevent the rise from taking place if it becomes a consistent or predictable phenomenon. There are also relaxation exercises that can help reduce the adrenaline production that occurs in different forms of sports and exercise.”

Scheiner noted that insulin reductions must be made carefully because too drastic a reduction can put individuals at higher risk for hyperglycemia, especially for those using a pump who take it off during activity. In addition, meal timing can play a large role in hyperglycemia related to exercise, with larger meals immediately preceding activity making post-exercise hyperglycemia more likely.

“If they ate something, let’s say within an hour … of the activity, a lot of that food is going to sit in their stomach and then digest and hit the intestines after the workout is over,” Scheiner said. “So it’s just a matter of if you can predict that sort of thing.”

Adequate planning can help someone with diabetes avoid diabetic ketoacidosis following physical activity, as well. If ketones are positive, exercise should be avoided. If there is unexplained high blood glucose level, individuals should reduce their correction bolus insulin by 50%, properly hydrate and limit the amount of time in which an insulin pump is disconnected, according to Scheiner.

Unforeseen obstacles

Continuous glucose monitoring can be incorporated into the exercise routine to improve glycemic management, including protecting against delayed-onset hypoglycemia, as the technology allows for foresight into future glucose levels.

“It’s probably the most valuable tool for anybody with diabetes who exercises,” Scheiner said. “You might have a great glucose for a workout, but if it’s dropping quickly, you know you’re going to need to eat or delay the workout a little bit. If it’s rising, your adjustments are going to be very different.”

For all the measures that can be taken to protect against highs and lows before, during and after exercise, there are outside factors that can make glycemic management more difficult. This includes extreme temperatures and insulin injection site.

“[There are] a lot of variables that patients have to contend with,” said Scheiner, who is collaborating with JDRF on a webinar series aimed at improved education about exercise in diabetes. “If we manage the major ones, if they adjust their insulin beforehand and during, if they use snacks intelligently and just make sensible choices … they have a much better chance of controlling their glucose effectively.” – by Phil Neuffer


Scheiner G, et al. S04. Presented at: American Association of Diabetes Educators; Aug. 9-12, 2019; Houston.

Disclosure: Scheiner reports no relevant financial disclosures.