Matching bolus insulin doses to carbohydrate food eaten
Artwork entered into the Life for a Child Art Competition by Mychel Montenegro, age 25, Bolivia
Dear Colleagues,
Management of type 1 diabetes is a balancing act with three major players – insulin, food and exercise. This is not easy, particularly for children and adolescents, with all the excitement and changes that are happening in their lives. But, when it is done well, young people with diabetes can lead normal and active lives and avoid long-term diabetes complications.
Life for a Child is slowly introducing Basaglar (insulin glargine) into our supported countries and is encouraging the transition to a basal-bolus regimen (also referred to as multiple daily injections or MDI regimen). This regimen allows for more flexible eating, and can reduce the risk of hypoglycaemia.
What is basal-bolus regimen?
Basal insulin
Long acting analog such as insulin glargine, also called basal insulin, is usually given once daily (at the same time every day) and provides an approximately 24-hour slow release basal coverage without a peak action as shown in the graph below.
Blood glucose level rise after each meal is shown in purple
Adapted from White JR, et al. Postgrad Med. 2003;113:30-36.
Bolus insulin and Insulin-to-Carbohydrate Ratio (ICR)
Short acting insulin such as Humulin Regular (R) – also called ‘bolus’ or ‘meal’ insulin - should be given before every meal that contains carbohydrate (see graph above). Ideally, the bolus dose should be calculated for the amount of carbohydrate in the meal. This is called the insulin-to-carbohydrate ratio (ICR). The initial ICR can be calculated by using the ‘500 rule’ i.e. 500 divided by the usual total daily dose (TDD = basal and bolus insulin).
Example: Patient is going to eat 45 grams of carbohydrate with his evening meal. His TDD is 36 units, therefore his ICR is: 500÷36=14 (rounded). This means 1 unit of Regular insulin will cover 14 grams of carbohydrate food. He is eating 45 grams of carbohydrate (45÷14) = 3.2 units; therefore, the patient needs 3 units of Regular insulin to cover the 45 grams of carbohydrate.
The insulin-to- carbohydrate ratio (ICR) indicateshow much carbohydrate (in grams) is covered by one unit of Regular insulin.
The bolus dose can then be adjusted according to blood glucose levels (BGL). Approximately fifteen minutes after eating ‘carbohydrate containing food’, the BGL starts to rise and reaches a peak around 1 hour and then slowly falls again. The BGL should be back to the target range of 5.0 - 10.0 mmol/l (90 - 180 mg/dl) within 2-3 hours after eating.
How much the BGL raises and falls depends on how accurately the bolus insulin dose is matched to the amount of carbohydrate eaten. In the graph above the bolus insulin dose is matched perfectly.
Tips for Regular (bolus) insulin
Regular insulin should be injected 20-30 minutes before the meal unless the BGL is under 5.6 mmol/L / 100 mg/dl - then take insulin right before eating
Keep Regular doses at least 3-4 hours apart to avoid “stacking” of insulin (which increases the risk of hypoglycaemia)
As Regular insulin lasts at least 5 and up to 8 hours, there is a risk of hypoglycaemia. Therefore, a carbohydrate snack may need to be eaten between meals (less than or equal to 15 grams), if there is more than 5 hours between meals
The BGL 2-3 hours after a meal is used to adjust the Regular dose for that meal in the future.
How to count carbohydrate (carbs) amounts in a meal?
Carbohydrate counting – also referred to as carb counting – is a way of estimating the amount of carbohydrate in different foods. This will help to more accurately match the insulin doses to the amount of carbohydrate food eaten and avoid extreme fluctuations in blood glucose levels.
Carbohydrate containing foods are:
Starchy foods such as grains (e.g. bread, cereals), starchy/root vegetables (e.g. potato, corn, yam, cassava), rice, pasta, and lentils, chickpeas and other legumes
Sugars such as the natural sugar in fruit and milk and the added sugar in soft drinks, sweets, biscuits, chocolates and many packaged foods.
Carbohydrates are measured in grams (g) and may be counted in grams, exchanges or portions.
To count carbohydrates:
Identify the foods in the meal or snack that contain carbohydrates (e.g. rice, lentils etc)
Measure the foods containing carbohydrates (using measuring cups, spoons or kitchen scales to measure how much of the carbohydrate food will be eaten e.g. 1 cup of rice and 2 oranges).
Calculate the amount of carbohydrates in grams (use suggested tools below)
Tools to help you count carbohydrates
Websites (just google ‘carbohydrate counting’ in your language)
Refer to food labels on packaged food
Smartphone apps (search Google Play store, Apple store)
Measuring cups and spoons, kitchen food weighing scales.
Using the patient’s hand is a simplified way of measuring carbohydrate portion sizes. Use the patient’s palm to have them describe how much carbohydrate they have at each meal.
Children and adults with diabetes can have the occasional treat/sweet just like other children so they don’t feel deprived and excluded. But they should calculate the carbohydrate amount and cover it with short acting insulin to avoid a high blood glucose level after eating a sweet.
A word on exercise
Remember that exercise utilises insulin more efficiently for many hours after. Therefore, before planned exercise insulin doses can be reduced or additional carbs eaten to prevent hypoglycaemia.
If you would like to work with a local dietitian and Life for a Child to produce a carbohydrate counting book like the one for India with your local foods and in your language, or have your own carb counting resource that you are willing to share, please contact me via email: [email protected]
