Using ExCarbs to prevent low blood sugars

Low blood sugars can be a challenging and frustrating part of exercise when you live with diabetes.

Often, preventing low blood sugars during/after exercise requires planning and adjustment of insulin. Even more challenging is when exercise is unplanned, and insulin has already been taken. In this case, extra carbs need to be taken to prevent low blood sugars.

If you are tired of guessing how much carb to take, or how much to reduce your insulin, try using the ExCarbs method to give you a more accurate way of planning your exercise and preventing low blood sugars.

What are ExCarbs?

ExCarbs are extra carbohydrates needed for exercise. Taking ExCarbs can help prevent low blood sugars during/after exercise. ExCarbs can also help adjust your bolus insulin at the meal before exercise to prevent lows. The idea is to eat the amount of carbs that you guess your body will use during that activity, with the end result being that your blood sugar stays relatively stable without dropping or spiking much.

How much ExCarbs do I need?

The amount of ExCarbs you will need depends on your weight and the type of activity you will be doing.

If you have access to an ExCarbs table then you can determine an approximate amount of carbohydrates, in grams, that you will need based on your weight and type of activity.

If you do not have access to a table or the activity that you are doing is not listed on the table, you can use a simple estimation of approximately 1g carbohydrate per kg body weight per hour. As an example, a 65kg person would need to take approximately 65g of ExCarbs per hour of activity.

Using ExCarbs to Reduce Bolus Insulin

If you prefer not to consume ExCarbs, you can plan ahead for exercise and use ExCarbs to calculate how much to reduce your bolus insulin dose by to prevent low blood sugars.

To do this, use the ExCarbs table or simple estimation (1g/kg/hr) to determine how many grams of ExCarbs are needed. Then, count the carbohydrate in the meal you will eat prior to exercise. Subtract the number of ExCarbs grams from the grams of carbohydrate from your meal. Now, use your carbohydrate ratio to determine the dose of rapid insulin you will need to cover the remaining grams of carbohydrate.

For example, a 150lb woman plans on walking 4.5mph for 1 hour just after eating her lunch. Based on the ExCarbs table, she will need 45g of ExCarbs for this activity. She is planning on eating 60g of carbohydrate at her lunch meal. Her insulin-to-carbohydrate ratio is 1:5.

60 (g of carb in meal)-45 (g of ExCarbs) =15g

15g (remaining)/5 (carb ratio) = 3

She will need to take 3 units of rapid insulin to cover this meal, instead of her usual 12 units if she did not account for ExCarbs.

The most important thing to remember about exercise, insulin and ExCarbs is that this is not a perfect science! You will still need to check your blood sugars regularly, including before, during and after exercise to see how your adjustment is working. Remember that ExCarbs estimation and the ExCarbs table are only approximate, and that you will need to adjust your plan based on experience.

Want to know more about ExCarbs? Check out these resources, or book an appointment with your diabetes educator.

Pumping Insulin Fourth Edition by John Walsh, P.A. C.D.E and Ruth Roberts, M.A.

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