Diabetes Exercise Physiology 200 – Insulin

This is part two of what I learned from TeamWILD.

  • If you’re over-insulinized, you’re BG might not be low and you might not have the same symptoms as hypoglycemia, but it can lead to rapid drops in blood glucose and sub-optimal athletic performance. (Under-insulinization also leads to poor performance.)
    • Too much basal insulin often exhibits as a drop of 30-90 mg/dL (1.6-5.0 mmol/L) per hour during exercise.
    • Too much bolused insulin often causes a drop of 120-240 mg/dL (6.7-13.3 mmol/L) per hour.
  • Previous hypoglycemia and/or exercise changes insulin sensitivity and the amount of available glycogen for this workout, which can make hypoglycemia more likely. (More details about glycogen.)
  • The adrenaline response (for example, caused by race anxiety) can cause under-insulinization because it causes glucagon-like dumping of glucose from the liver.
  • Aim for blood glucose of 70-180 mg/dL (3.9-10.0 mmol/L) during exercise.
  • Be proactive. Make a fuel and insulin plan and then prepare for the unexpected.
  • Fuel exercise, not blood sugar. Get the insulin right for exercise first, then the diabetes.
  • For performance, favor fueling over insulin reduction. Match insulin to food.
  • Basal adjustments should not be needed for exercise of about 60 minutes or less. Never reduce more than 50%. Reduce 60-90 minutes prior to exercise.
  • Avoid bolusing during exercise. However, do mini-boluses for highs during exercise (> 200-250 mg/dL, 11.1-13.9 mmol/L).
  • Insulin on board (IOB) is the biggest predictor of BG changes during exercise.
  • Typical bolus adjustments for a pre-exercise meal (60+ grams of carb)
    • 1 hour before —> Reduce 50% (not recommended)
    • 2 hours —> 20-30%
    • 3 hours —> 10-20%
  • This is different for a pre-exercise snack, which probably won’t need any insulin at all.
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One Response to Diabetes Exercise Physiology 200 – Insulin

  1. StephenS says:

    I’ve been having a LOT of trouble with this lately. My endo basically told me that I’m tired all the time, and having trouble with hard, strong workouts because I’ve been over-insulinized lately. Thanks for spelling it out in terms I can understand. It’s a great reference. Thanks!

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