Insulin dose adjustment for physical exercise

David Kinshuck







Principles of exercise and activity

Exercise helps our general health. You can exercise as often as you like, and participate in a wide variety of sports and activities. For some dangerous activities, e.g. diving, you may need specialist advice.

A person without diabetic does not have hypos during exercise. Their body naturally reduces the amount of insulin releaaed.Also, increased activity of any sort will speed up the rate at which you use glucose, as it is burned up for energy. Therefore, it is important to plan ahead to prevent unnecessary hypos during or after your activity.

Exercise that is very much more than you are used to (either more vigorous or more prolonged) may keep your blood glucose low for up to 18 hours afterwards. This is due to the body replacing the glucose it had stored in its muscle, which was used for the exercise. This does not just apply to sport. It also applies at other times of increased physical activity e.g. spring cleaning, moving house, shopping, sex, or gardening.

Things to consider when planning physical activity or exercise:

Hypos can be prevented either by reducing your insulin or increasing carbohydrate intake during and/or after the exercise.


Options for activity and exercise


Planned physical exercise
aim to lose weight focus on reducing insulin
weight not an issue focus on increasing carbohydrate or reducing insulin
Unplanned activity or exercise
Only option is to increase carbohydrate



Insulin adjustment

It is not possible to give exact dose reductions. You need to determine the effect of exercise on your blood glucose by self-monitoring and adjusting your insulin dose.

If your diabetes is poorly controlled or your blood glucose is raised (e.g. over 13mmol/l) prior to exercise, the exercise probably will not lower your blood glucose level significantly. It is likely that your blood glucose level will rise....this is because you probably do not have enough insulin circulating in your body. Consider injecting an extra dose of quick-acting insulin to reduce the level before your exercise, and always check for ketones.

If ketones are present in your urine you need to avoid exercise until your blood level is below 13mol/l. Follow the advice given for positive ketone tests.


If the activity is less than 45 minutes duration
blood glucose level action
using a pump see with a pump
less than 7mmol/l take 2-3 CPs depending on how strenuous the activity is.
7-10mmol/l take 1-2 CPs depending on how strenuous the activity is.
  • no extra CPs needed.
  • Consider when you last ate?
  • Is your insulin running out?
  • If the activity is more than 30minutes, retest (you may need extra CPs as above)
more than 13 mmol/l Test for ketones. If ketones positive, postpone exercise and consider extra quick-acting insulin


Type of exercise


type of exercise example action
short-term--gentle walk to shop - 20 minutes do nothing, carry rapid action carbohydrate
medium-term--gentle bike ride -- 35-45 minutes additional 1-2 CPs
Prolonged/intense--upto 4 hours aerobic class 1 hour cycling 4 hours 30-50% reduction in insulin dose prior to exercise Extra CPs may be needed.
Prolonged exercise
longer than 4 hours
a day hiking
  • reduce both long acting and quick acting insulin before exercise by 50%
  • Reduce any insulin during exercise by 50%
  • Reduce dose immediately after by30-50%
  • Increase carbohydrate snacks may be be necessary

There is an increase risk of hypos for some time after exercise whilst the body is replacing its used energy stores. The background dose in the evening and possibly the following morning after prolonged exercise may also need to be reduced 10-20%.

For Lantus users you may need to focus on quick-acting insulin and/or eating more CPs, rather than reducing the Lantus. A twice day background insulin, such as Levemir, may be better. Lantus lasts nearly 24 hours or even longer, whereas Levimir is shorter acting, and so Levemir is easier to adjust for prolonged exercise.

'The Diabetic Athlete', Sheri Colberg gives expert advice, and is worth buying or reading (you can usually ask your local library to get a copy).

DK  recommends insulin pumps if you take a lot of exercise, particularly if you take a lot more on some days than others.  See for expert advice.


Advice from Good Hope

This is an extract from Dr Sharon Jones, Nov 2006, talk for professionals, here 5mb powerpoint : Exercise in diabetes. aerobic, anaerobic exercise. Improve/maintain health. Exercise helps even if no weight lost. Hypos and avoiding them, pregnancy, neuropathy. The athlete, pre-& post exercise. Fluids, monitor glucose level. Slow and steady, weight loss programs, housebound programs, case examples.

This author strongly recommneds insulin pumps and sensors for everyone with type 1 diabetes, butespecaially those taking regular exercise

Here are some of the case examples.

  1. Runner
    • uses novarapid  before meals and detemir twice daily
    • runs after after breakfast
    • sips a sugary drink during the run
    • reduces breakfast novarapid 25%, with lighter breakfast
    • Usual insulin with increase CHO for lunch
    • If exercises before breakfast- Less sugary drink during the run - just as needed - normal insulin with breakfast after run
  2. Football team, both midfield player and goalie have type 1 and are treated with basal bolus insulin
    • Pre match meal-- Midfielder reduces bolus insulin by 50-75% -- Goalie by 25%
    • Pretraining meal-- Both midfielder and goalie reduce insulin by 40% -- And basal by 10%
  3. Rower...training - reduce insulin, more so if cold, hot or windy
  4. Racing - check glucose pre-race and give extra units if raised anticipating further rise from anaerobic metabolism
  5. Tennis - greater reduction in dose if playing singles than doubles
  6. Golf - usual reduction of around 20% with snacks each hour (half banana) but even less insulin or more snacks if caddie fails to turn up