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U-M Health SystemThis information is approved and/or reviewed by U-M Health System providers but it is not a tool for self-diagnosis or a substitute for medical treatment. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition.

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Diabetes: Counting Carbohydrates Meal Plan

What is the counting carbohydrates meal plan?

Counting carbohydrates is a meal plan that involves matching your insulin dose to the amount of carbohydrates (carbs) you eat. Carbs supply energy for your body  and affect your blood sugar level more than any other nutrient. The main goal of this food plan is to balance your insulin dose with the carbohydrates you eat.

How is this plan different from the exchange or constant carbohydrate meal plans?

This plan is different because the insulin dose and carbohydrates are not always the same day to day. This plan is more flexible. Most people start using this plan after they are familiar with how their body responds to food choices and have become comfortable with insulin.

How does this plan work?

First, you and your health care provider need to figure out how much insulin you need to balance the amount of carbohydrate you eat. There are two ways to figure this out:

  • Units per carb choice (exchange): Count carbohydrates in portion sizes of 15 grams (this is called a carb choice or an exchange). You take a set number of units for every carb choice that you eat.

To find out how many carb choices you eat, divide the number of grams of carbohydrate in a food by 15. For example, if a container of yogurt with fruit has 45 grams of carbohydrate, it contains 3 carb choices.

You then take the units of rapid or short-acting insulin (Humalog/NovoLog or Regular) you need to match the number of carb choices you are eating. For example, if you need 1 unit of insulin for every carb choice, then for 3 carb choices, you need 3 units of insulin (1 x 3 = 3).

Units of insulin per carb choice x the number of carb choices = total units of insulin.

  • I/C ratio: Other people use an insulin-to-carbohydrate ratio (I/C ratio) to figure out how much insulin to take. If you use a ratio, you still need to count the grams of carbs but you do not need to convert the grams to carb choices. You base the dose on grams of carbohydrates.An example of an I/C ratio is 1 unit of insulin for every 10 grams of carbs you eat.

For example, if you plan to eat 60 grams of carbohydrate and your I/C ratio is 1/10 (0.10), then you need 6 units of insulin (60 X 0.10 = 6).

Grams of carb x I/C ratio = units of insulin.

You can work with your health care team to figure out your I/C ratio.

Will I need to make more adjustments to the insulin dose?

After you figure out the number of units of insulin you need to take for the amount of carbs you eat, you may need to adjust the dose further. These adjustments are based on planned exercise, blood sugar levels, or other factors that may affect blood sugar such as illness, stress, or menstrual periods. For example, you may need to reduce the dose of insulin if your blood sugar level is low (below 70 mg/dl). You may need to increase the dose if your blood sugar is too high (above 180 mg/dl). Your dietitian and health care provider will give you guidelines for making these adjustments. The insulin dose calculated from the I/C ratio is usually reduced if it is given before strenuous exercise or at bedtime.

Which foods have carbohydrates?

Carbohydrates are found in many foods including:

  • starchy foods (such as breads, cereals, rice, starchy vegetables, and pasta)
  • fruit
  • milk and yogurt
  • sweets.

To see a list of carb choices, you can order the Exchange List for Meal Planning from The American Diabetes Association and the American Dietetic Association (1-800-342-2383). Although this book is often used for the exchange diet, it lists the carbohydrate content for lots of foods and is very useful. Nutrition labels on food packages also list the grams of carbohydrate in a serving of food.

When should I take insulin?

In general, you need to take insulin at a time that allows the insulin to start working as carbohydrates are absorbed into the blood.  Your blood sugar starts to rise about 10 minutes after you start to eat.

  • Humalog/NovoLog begins working in 10 minutes. The peak activity of this insulin is 30 to 90 minutes after you take it. Take this insulin right before you eat.
  • Regular insulin begins working in 20 to 30 minutes. The peak activity is 2 to 4 hours after taking. Take this insulin 20 to 30 minutes before you eat.

How do I get started?

  1. Keep a careful record of food, insulin, blood sugar levels, and exercise for at least 3 days. Measure your blood sugar 2 hours before meals and 2 hours after meals. Record all doses of insulin or oral medicines you take.
  2. You and your health care team will analyze the report and decide how much insulin you need to take to balance the amount of carbohydrates you eat.
  3. Start counting carbs and give insulin to match. It helps to keep careful records for the first 1 to 2 weeks of:

·        the number of carbohydrates you eat at each meal or snack

·        your insulin doses

·        your blood sugar levels (especially 2 hours after meals).

  1. If the blood sugar values are not in your target range, then your insulin doses need to be changed.  Review your records with your team to see if any adjustments need to be made. Your insulin doses may need to be adjusted periodically.


Reviewed and updated by Martha Funnell, MS, RN, CDE, Michigan Diabetes Research and Training Center, August, 2004.

Abstracted from the book, "Understanding Diabetes," 10th ed., by H. Peter Chase, MD (available by calling 1-800-695-2873).
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright © 2003 McKesson Health Solutions LLC. All rights reserved.
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