Keep a record
Testing your blood glucose levels before, during and after a training session requires a blood glucose meter that is easy to use while exercising. Keep a record of your readings in a training log, and record details of the distance and time of the session, the food eaten and insulin doses taken so that you can establish a pattern of likely insulin needs and glucose requirements for future sessions. You may also like to discuss these with your diabetes care team.
Test results
Depending on the results of your pre-activity blood glucose test, you may well need to eat some starchy carbohydrate food before you start. If the test shows that your blood glucose level is 13mmol/l or above, you must also test for ketones (test strips are available from your GP). Even if ketones are not present, there may still not be enough insulin for your muscles to be able to mobilise the energy needed to exercise. Your blood glucose level will rise further as a response to the activity and yet, without insulin, still not provide the muscles with energy. Delay the training session until your insulin has taken effect and your blood glucose level has come down.
If ketones are present, this indicates that fat is being metabolised for energy. If a positive ketone test accompanies a high blood glucose level, this may be a sign of ketoacidosis and you should seek medical help immediately.
Recovery time
It is important to realise that your body takes up to 36 hours to recover from strenuous activity. The process of muscle refuelling will continue to use up any carbohydrate that is eaten until the muscles are replenished. Be aware of the risk of hypos - not only overnight but also the following day. Have a bedtime snack and monitor your blood glucose level when you wake.