Intensive insulin therapy, using either an insulin pump or multiple daily injections, is the preferred treatment for people with type 1 diabetes. With the use of these regimens, an individualized carbohydrate-to-insulin ratio is required to allow greater flexibility in the timing, amount and frequency of meals. Since insulin is needed for the uptake of carbohydrate in the body, only foods that contain carbohydrates need to be counted. Hence it's called the insulin-to-carbohydrate ratio, which is the amount of carbohydrate you can have for each unit of insulin.
Step 1
Determine your total daily dose of insulin (TDD). TDD for an adult with type 1 diabetes can be estimated by multiplying the patient's weight in kg by 0.7. Adolescents may require more insulin, and older adults may require less. For example:
TDD for a 65 kg woman = 65 * 0.7 = 45.5 units
TDD consists of basal and bolus insulins. Basal insulin keeps blood glucose levels stable overnight and when the patient has not eaten, and bolus is the insulin needed for the uptake of carbohydrate after a meal.
Step 2
Calculate the insulin-to-carbohydrate (I:C) ratio using the 500 rule, a common method. This approach is based on the assumption that the average person consumes, from meals and snacks, and produces, via the liver, a total of approximately 500 grams of carbohydrate daily. The I:C ratio equals 500 divided by the TDD. For the above example:
I:C = 500 / 45.5 = 11 grams of carbohydrate covered by one unit of fast-acting insulin
Step 3
Fine-tune the method you use to achieve optimal blood glucose control. Different doctor or diabetes team may use different methods to calculate the I:C ratio depending on their experiences.
Step 4
Self-monitor your blood glucose for up to six to eight times (including before and 2 hours after meals) per day using the I:C ratio. Count your carbohydrate accurately and make note of any changes in your activities, stress level, unusual food intake, etc.
Step 5
Eat foods that are easier to count (e.g., baked potato instead of baked casserole) in the beginning. If you have the right I:C ratio, your blood glucose level should return to your premeal level 3 to 4 hours postmeal.
Step 6
Decrease your I:C ratio slowly if your blood sugar is below the expected range, and vice versa until you reach an optimal blood glucose level. For example, increase the number of carbohydrates by 5 grams for each unit of insulin. Fine-tuning is best done when you have a stable basal rate, that is, your blood sugar level remains steady overnight and when you fast during the day.
Tips and Warnings
- The success of finding the right I:C ratio depends on your motivation and willingness to work closely with the diabetes care team. The American Diabetes Association has information on carbohydrate counting on its website. A lot of the nutrition facts labels on food packages also include dietary exchanges.
- The 500 rule provides a rough estimate of your I:C ratio. Some people may be more insulin-resistant, and some may be more insulin-sensitive due to the difference in body composition. Even within the same individual, the I:C ratio may change due to change in lifestyle, growth, puberty, weight and the presence of other medical conditions. Check with your doctor and diabetes care team whenever you make adjustments to your insulin.
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