Counting carbohydrates is an important skill for people with diabetes to acquire to help keep blood glucose (glucose) levels under tight control, to help make more flexible and varied food choices, and to increase confidence in disease management.
- Counting carbohydrates helps keep blood sugar at target levels.
- Counting carbohydrates regulates the dose of insulin needed. The amount of insulin needed depends on the amount of carbohydrate consumed at a meal or snack. The insulin-to-carbohydrate ratio (ICR) is calculated using the formula to find the required insulin dose.
- Carbohydrate factors may be different for each person. Patients can record their diet and measure their blood glucose after each meal, and the physician can work with the patient to determine the appropriate value.
How do I calculate carbohydrates in my diet?
To calculate the carbohydrates for a meal, you need to know the carbohydrate content of each food. Be careful to count the whole food, down to a slice of bread, a plate of lettuce, or a spoonful of salad dressing. Most packaged foods will state on the label how many carbohydrates are in a serving. You can also ask a diabetes professional for information about carbohydrates.
To know the carbohydrate content of a non-packaged food, you need to know the standard carbohydrate content of the food. There are about 15 grams of carbohydrate per serving or standard serving. The carbohydrate content of each meal can be used to calculate the dose of insulin needed.
For example, your doctor recommends 1 unit of rapid-acting insulin for every 10 to 15 grams of carbohydrate you eat. If there are 50 grams of carbohydrates in a meal, 5 units of insulin should be injected to keep postprandial blood glucose at target levels.
The insulin-carbohydrate factor can change over time. Some people may have different coefficients for both lunch and dinner. For example, you need 1 unit of insulin for every 10 grams of carbohydrate at lunch, but only 1 unit of insulin for every 15 grams at dinner.
Remember these tips when counting carbohydrates:
- Control the amount.
- It’s important to control the amount. If the package says 2 servings of carbohydrates, you should double the amount per unit if you eat all of it.
- Protein, fat, and dietary fiber have little effect on blood sugar. The conversion of carbohydrates to glucose is slower when these foods are consumed in large amounts in a single meal.
- Higher-order carbohydrate calculations need to take into account the amount of dietary fiber or sugar alcohols in the food. If a food contains 5 grams or more of dietary fiber, you can subtract half the weight of the dietary fiber from the total carbohydrate of the food. For example, a food containing 30 grams of carbohydrate and 8 grams of dietary fiber is equivalent to a food containing 26 grams of carbohydrate. When using rapid-acting insulin, you also need to be careful if the food contains more than 5 grams of sugar alcohols. Halve the amount of sugar alcohols and subtract the corresponding value from the total carbohydrate.
- Exercise affects blood glucose. People who exercise have less insulin requirements than those who don’t exercise. However, the timing of exercise needs to be kept in mind. For example, if you exercise within 1 hour of a meal, your body needs less insulin to digest food than if you exercise 3 hours after a meal.
Record what foods you eat, measure your blood sugar after meals and exercise to see how protein, fat, dietary fiber and exercise affect your body’s insulin needs.