By Sheri Colberg, PhD
Iatrogenic hypoglycemia (i.e., blood glucose levels of <70 mg/dl or <3.9 mmol/L caused by diabetes treatment) is one of the chief barriers to optimal glycemic control in people with type 1 diabetes (T1D)1.
Severe hypoglycemia is a common contributor to morbidity and mortality and a major fear for people with diabetes and their families. Fear of hypoglycemia and its avoidance are predominant limiting factors in achieving normal or near normal blood glucose levels 2,3.
In prediabetic individuals or those who have type 2 diabetes (T2D) controlled with diet and exercise alone, the risk of developing hypoglycemia related to physical activity is minimal. In individuals managing T2D with diet and exercise alone, the risk of developing hypoglycemia during or after any physical activity is minimal, even though undertaking longer duration and lower intensity exercise generally reduces glycemic levels4. In anyone who uses insulin or select insulin secretagogues (that stimulate the secretion of insulin) — whether someone with T1D, T2D, or gestational diabetes (GDM) — engaging in physical activity has the potential to significantly lower blood glucose levels both during and after exercise5,6. Since the absorption and release of injected insulin cannot always be effectively controlled or anticipated, the additive uptake of blood glucose by muscle contractions and excess insulin in anyone taking insulin may result in hypoglycemia.
Physical activity can cause hypoglycemia both during and following sessions, and its risk is affected by a number of factors, including exercise type, duration, and intensity; insulin and other medication doses (Table); and food intake. Diabetic individuals at higher risk of developing it will benefit from gaining a better understanding of its causes, symptoms, treatments and learning preventative measures. Both severe hypoglycemia and hypoglycemia unawareness are prevalent obstacles in its detection, treatment, and prevention. Various strategies and technologies currently are used to help detect and prevent it, including improved patient education, frequent self-monitoring of blood glucose (SMBG), use of rapid-acting and basal insulin analogs, insulin pump therapy, exercise-related insulin adjustments, and continuous glucose monitors1.
Table. Risk of Hypoglycemia with Use of Diabetes Medications
No Risk or Minimal Risk
(Generic name: Brand name)
(Generic name: Brand name)
Metformin and Combinations:
Exenatide: Byetta (daily), Bydureon (weekly)
Glipizide and Combinations:
Glucotrol, Glucotrol XL
Glyburide and Combinations:
DiaBeta, Glynase, Micronase, Pres Tab
Insulin: All types and delivery methods
All incidences of hypoglycemia should be treated with ingestion of rapidly absorbed carbohydrate sources, such as glucose tablets or gels, hard candy, regular soda, skim milk, cake icing, or juice1,7. Ingestion of 15–20 g of glucose is the preferred treatment for hypoglycemia when an individual is conscious, although any form of carbohydrate that contains glucose may be used. If blood glucose levels measured 15 min after treatment are still too low, the treatment can be repeated, and a later meal or snack may be needed to prevent recurrence.
If an individual is unable to self-treat with glucose ingestion or is unconscious, treatment with glucagon injection by a family member, friend, or caregiver instructed on its administration is advised. Individuals at risk for severe hypoglycemia are advised to keep glucagon on hand at all times. If no glucagon is available, medical treatment should be initiated with a phone call to emergency services.
In summary, detection, treatment, and prevention of hypoglycemia related to physical activity participation are critical and frequently require self-monitoring and diabetic regimen changes. Given that fear of hypoglycemia is a significant barrier to exercise participation, diabetic exercisers need to better understand its causes and how to prevent it effectively. Individuals may choose to reduce doses of certain insulin before, during, and after activities to accomplish this, or they may increase their intake of carbohydrates and other foods. Making appropriate regimen changes to compensate for prior physical activity may also be effective in preventing delayed-onset and overnight hypoglycemia.
- Realsen, J. M., and H. P. Chase: Recent advances in the prevention of hypoglycemia in type 1 diabetes. Diabetes Technol Ther 13 (12):1177–1186, 2011
- Brazeau, A. S., R. Rabasa-Lhoret, I. Strychar, and H. Mircescu: Barriers to physical activity among patients with type 1 diabetes. Diabetes Care 31 (11):2108–2109, 2008
- Ross, S. A., H. D. Tildesley, and J. Ashkenas: Barriers to effective insulin treatment: the persistence of poor glycemic control in type 2 diabetes. Curr Med Res Opin 27 (Suppl. 3):13–20, 2011
- Evans, E. M., S. B. Racette, L. R. Peterson, D. T. Villareal, J. S. Greiwe, and J. O. Holloszy: Aerobic power and insulin action improve in response to endurance exercise training in healthy 77-87 yr olds. J Appl Physiol 98 (1):40–45, 2005
- Arutchelvam, V., T. Heise, S. Dellweg, B. Elbroend, I. Minns, and P. D. Home: Plasma glucose and hypoglycaemia following exercise in people with Type 1 diabetes: a comparison of three basal insulins. Diabet Med 26 (10):1027–1032, 2009
- West, D. J., J. W. Stephens, S. C. Bain, L. P. Kilduff, S. Luzio, R. Still, and R. M. Bracken: A combined insulin reduction and carbohydrate feeding strategy 30 min before running best preserves blood glucose concentration after exercise through improved fuel oxidation in type 1 diabetes mellitus. J Sports Sci 29 (3):279–289, 2011
- Chu, L., J. Hamilton, and M. C. Riddell: Clinical management of the physically active patient with type 1 diabetes. Phys Sportsmed 39 (2):64–77, 2011
This article is excerpted from Chapter 12 of Exercise and Diabetes: A Clinician’s Guide to Prescribing Physical Activity, a case-study based book available through the American Diabetes Association in June 2013 and written by Dr. Sheri Colberg (find more information about the book online at www.shericolberg.com/exercise-diabetes.asp).
In addition, anyone wishing to earn free CME credits through the ADA for completing a new self-assessment program on exercise and diabetes may do so now through the ADA’s web site at http://professional.diabetes.org/ce.
Copyright © 2013 Diabetes In Control, Inc.