Working with Active Individuals with Diabetes Who Use Insulin

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Given that in the United States alone, there are close to 30 million people who have diabetes and five to 10 percent of those have type 1 diabetes (and must use insulin), many of your clients may be insulin users. What’s more, a sizeable number of adults and youth with type 2 diabetes may take supplemental insulin as well. The reason that insulin use matters is that active individuals must balance out their blood glucose to be effective, and insulin can lower blood glucose too far and interfere with workouts and impair athletic performance.

As a fitness professional, how can you help these individuals be active? It is important that you understand a few key physiological concepts:

  • Blood glucose must be kept in a fairly tight range in order for individuals to be successfully active. This means that insulin and food may need to be adjusted to keep glucose from dropping too low or rising too high.
  • Insulin is the only hormone that the body uses to lower blood glucose, while five other hormones can raise it. Circulating levels of insulin during exercise can have a huge impact on how blood glucose reacts to being active because both insulin and muscle contractions cause muscles to take up and use blood glucose.
  • Hypoglycemia is typically the biggest threat to performing optimally and can cause people to fatigue early or underperform during athletic endeavors. On the flip side, having blood glucose levels well above normal (hyperglycemia) can also have a negative impact.
  • Carbohydrate is the body’s primary fuel during most moderate to vigorous activities. If an individual runs out of carbohydrate stores in muscles (glycogen) and “bonks” during an activity, performance will suffer.
  • A sizeable number of factors impact an insulin user’s blood glucose response to a given activity. Among other things, these include the type of activity, its intensity and duration, the frequency of being active, exercise timing, recent food intake, insulin “on board,” environmental conditions, previous bouts of hypoglycemia, hydration status, and other bodily concerns. In other words, responses can vary—even when someone does the same activity over again.

So, how can fitness professionals help these individuals the most?

  • Gain a basic understanding of how all these factors can impact exercise. No insulin user is going to expect his or her personal trainer, health coach, or other educators to understand the unique nuances of their management, but as the professional in the room, you should understand what is possible.
  • Learn to recognize the signs and symptoms of hypoglycemia and know when your client is most likely to experience it and know how to assist someone in treating hypoglycemia, should assistance be required.
  • Be ready to adjust their workouts when situations arise that warrant it. Some days they may simply feel better than others as a result of how their blood glucose has been managed before working out or while they are active.
  • Finally, keep in mind that while blood glucose responses may be somewhat predictable over time, every day is potentially a new day when it comes to balancing insulin use and exercise.


Sheri R. Colberg, PhD, FACSM, is the author of The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities (the newest edition of Diabetic Athlete’s Handbook), available through Human Kinetics (, Amazon (, Barnes & Noble, and elsewhere. She is also the author of Diabetes & Keeping Fit for Dummies. A professor emerita of exercise science from Old Dominion University and an internationally recognized diabetes motion expert, she is the author of 12 books, 28 book chapters, and over 415 articles. She was honored with the 2016 American Diabetes Association Outstanding Educator in Diabetes Award. Contact her via her websites ( and

FCEA Founding Member

Sheri Colberg, PhD, FACSM, is an author, lecturer, consultant, and professor emerita of exercise science at Old Dominion University and a former adjunct professor of internal medicine at Eastern Virginia Medical School. Having earned her undergraduate degree from Stanford University and a Ph.D. from the University of California, Berkeley, she has specialized in research on diabetes and exercise and healthy lifestyles and shaped physical activity recommendations for professional organizations, including the American College of Sports Medicine, American Diabetes Association, and American Association of Diabetes Educators. She has authored 12 books, 28 book chapters, and more than 400 articles on physical activity, diabetes, healthy lifestyles, and aging. In addition to her website, Diabetes Motion (, she provides education to fitness professionals working with people with diabetes through Diabetes Motion Academy ( and through her own website ( She is the 2016 recipient of the American Diabetes Association’s Outstanding Educator in Diabetes Award.

Author of: Working with Clients with Diabetes or Prediabetes Specialist Certificate Program / Working with Clients with Diabetes or Prediabetes Level 1 / Working with Clients with Diabetes or Prediabetes Level 2 / Working with Clients with Diabetes or Prediabetes Level 3.

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