Exercise Carbohydrate Calculators

Dear Dani, Grace and Jude,

Note: This page is advice for Grace, Jude and John. For any other reader, it’s information only. No therapeutic relationship is formed – read this.

I have pulled the international guidance together into a PDF that allows you to personalise carb amounts and glucose targets depending on the CGM you are using.

Here is an example for Grace’s swimming.

Grace, you weigh 20kg, use a Dexcom G6 (mmol/L), and have a low hypoglycaemia risk. Therefore, I made this chart for you.

You need to click down to the second page to get the carb amounts. You will need to check 20 minutes before and every 20 minutes during exercise


Here are the Exercise Carbohydrate Calculators to download for different CGM devices.

You will need Adobe to be able to use them, which you can get for a ComputerAndroid device or Apple device.

Dexcom G6 – Exercise Carbohydrate Calculator

Libre 1 & 2 – Exercise Carbohydrate Calculator

Medtronic – Exercise Carbohydrate Calculator

Dexcom G6 with pump – Exercise Carbohydrate Calculator

The key features of the Exercise Carbohydrate Calculators include:

  • The safest exercise glucose range is 7.0-10.0mmol/L (140-180mg/dL)
  • It’s ok to start exercise in the 5.0-7.0mmol/L (90-140mg/dL) range but a few more carbs will be needed
  • Check 20 minutes before exercise and every 20 minutes during to decide what action to take
  • The maximum is usually 20g of glucose in 20 minutes, remember the intestine can usually only digest 1g per minute. However, when the glucose is rapidly falling during exercise it’s safer to increase closer to 1.5g per minute
  • The weight is capped at 60kg so the number of carbs can never be above 30g in 20 minutes (1.5g/min)
  • As weight goes up, so does the glucose required
  • Change the glucose amount based on glucose value and trend arrow

Does it always have to be glucose?

Glucose is not the only option to supplement with during exercise, it’s just the best. Glucose is absorbed within 20 minutes and does not get trapped in the liver (unlike fructose).

Therefore, when you check every the CGM every 20 minutes, you can be fairly confident there is not a backlog of glucose soon the be absorbed.

This is not the case If you decide to use sugar, fruit, biscuits or something similar. You run the risk of slow glucose absorption and going low before it kicks in, followed by glucose stacking up to catch you out later. I am sure it can be done, it just does not seem optimal.

Dani, regular teeth bruising and use of xylitol chewing gum will stop any dental issues

Next step. For John -Deep Dive