A 28-year-old woman with type 1 diabetes mellitus comes to the office to discuss insulin management. She anticipates participating in a 5-km (3.1-mi) jog to raise money for diabetes research. The patient was diagnosed with type 1 diabetes mellitus 3 years ago and takes 16 units of insulin glargine at bedtime and 4-6 units of insulin lispro before meals. She is regimented with her meal timing (breakfast at 5:30 AM, lunch at noon, and supper at 5:30 PM) and recently added a small bedtime snack to prevent nighttime hypoglycemia. The patient is generally aware of hypoglycemic symptoms but had an episode of severe hypoglycemia 3 months ago, requiring emergency department care and intravenous glucose. She has no history of pregnancy and her menstrual periods are regular. The patient does not use tobacco or alcohol. Her mother has type 1 diabetes complicated by proliferative diabetic retinopathy. Physical examination is unremarkable. Hemoglobin A1c is 6.9%. The jog is scheduled to start at 6:30 AM, and the patient expects it will take her 45 minutes to complete it. She intends to have breakfast at her usual time of 5:30 AM on that day. Which of the following is the most appropriate adjustment in this patient's insulin dose on the day of the walk?

Question

A 28-year-old woman with type 1 diabetes mellitus comes to the office to discuss insulin management.  She anticipates participating in a 5-km (3.1-mi) jog to raise money for diabetes research.  The patient was diagnosed with type 1 diabetes mellitus 3 years ago and takes 16 units of insulin glargine at bedtime and 4-6 units of insulin lispro before meals.  She is regimented with her meal timing (breakfast at 5:30 AM, lunch at noon, and supper at 5:30 PM) and recently added a small bedtime snack to prevent nighttime hypoglycemia.  The patient is generally aware of hypoglycemic symptoms but had an episode of severe hypoglycemia 3 months ago, requiring emergency department care and intravenous glucose.  She has no history of pregnancy and her menstrual periods are regular.  The patient does not use tobacco or alcohol.  Her mother has type 1 diabetes complicated by proliferative diabetic retinopathy.  Physical examination is unremarkable.  Hemoglobin A1c is 6.9%.  The jog is scheduled to start at 6:30 AM, and the patient expects it will take her 45 minutes to complete it.  She intends to have breakfast at her usual time of 5:30 AM on that day.  Which of the following is the most appropriate adjustment in this patient's insulin dose on the day of the walk?

Quizplus · Accepted Answer

Explanation: Physical activity promotes noninsulin-mediated uptake of glucose into skeletal muscles and increases the risk for hypoglycemia in patients with diabetes. This risk is greater in patients with type 1 diabetes mellitus and in those with type 2 diabetes treated with insulin or insulin secretagogues (eg, sulfonylureas). To reduce the risk of hypoglycemia during exercise, patients should decrease the dose of short-acting insulin within 1-3 hours prior to exercise, with the reduction proportionate to the intensity of exercise. If the exercise is expected to be prolonged (>60 minutes) or will occur in the morning before breakfast, the dose of basal insulin should also be reduced. However, basal insulin does not need to be reduced for shorter durations of exercise, as in this patient (Choice C). If blood glucose is <100 mg/dL before, during, or after exercise, additional carbohydrates (eg, fruit juice) should be consumed. Following exercise, a snack containing complex carbohydrates (eg, granola) can prevent delayed hypoglycemia. Additional measures include maintaining oral hydration and avoiding insulin injections into exercising limbs. (Choice A) Decreasing the dose of lispro before lunch may not be necessary for this patient as she will be able to eat her lunch after completion of the event. (Choice D) Completely skipping insulin doses in patients with type 1 diabetes can lead to severe hyperglycemia and possibly ketoacidosis. (Choice E) Keeping the same insulin regimen would increase the risk of hypoglycemia. Educational objective: In patients with diabetes mellitus treated with insulin, a reduction of the insulin dose before physical activity is recommended to prevent hypoglycemia, with the dose reduction proportionate to exercise intensity. Intake of additional carbohydrates can also reduce the risk of hypoglycemia. References: Insulin therapy and exercise. (http://www.ncbi.nlm.nih.gov/pubmed/21864755)

A 28-Year-Old Woman with Type 1 Diabetes Mellitus Comes to the Office