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Diabetes: Counting Carbs if You Use Insulin

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Carbohydrate counting is an important skill to help you maintain tight control of your blood sugar (glucose) level when you have diabetes. It gives you the flexibility to eat what you want and increases your sense of control and confidence in managing your diabetes.

  • Carbohydrate counting helps you maintain your blood sugar at your target level.
  • Carbohydrate counting allows you to adjust the amount of insulin you take based on how many grams of carbohydrate you eat at a meal or snack. The formula used to determine the amount of insulin you need is called the insulin-to-carbohydrate ratio.
  • The insulin-to-carbohydrate ratio differs from one person to another. You and your doctor will calculate your ratio by recording the food you eat and testing your blood sugar level after meals.

Carbohydrate counting is a recommended method of meal planning for people who have diabetes. It involves matching your insulin dosage to the grams of carbohydrate in the foods you eat to keep your blood sugar level in your target range.

Carbohydrate—the body's main source of glucose—affects blood sugar more than any other nutrient. All forms of carbohydrate increase your blood sugar level. Foods that contain carbohydrate include:

  • Fruits and vegetables.
  • Milk and yogurt.
  • Starchy foods (such as breads, cereals, dry beans, and vegetables such as potatoes and corn).
  • Sugary foods (such as candy and cakes).

Contrary to what you may have heard, you can eat sugar when you have diabetes. But if foods that contain sugar make up a large part of your diet, you are probably not eating enough of other more nutritious foods.

Test Your Knowledge

Which of these foods contain carbohydrate?

Wheat bread, rice, peas, and oatmeal
Cheesecake, skim milk, and pears

Carbohydrate counting helps prevent low or high blood sugar levels, which can cause medical emergencies. Over time, high blood sugar levels can damage many body tissues and organs.

Counting carbohydrate grams allows you to match insulin to the food you eat every day to keep blood sugar at your target level. This method is effective because carbohydrate is the main nutrient that causes blood sugar to rise after meals, increasing the need for insulin. Carbohydrate turns into glucose within 2 hours after you eat.

If you use an insulin pump or take multiple insulin injections, you need to know how many grams of carbohydrate are in a meal to calculate how much rapid-acting insulin to take before you eat. A pump provides a continuous (also known as basal) rate of insulin throughout the day, but it must be programmed at meals to provide extra insulin to allow for the rise in blood sugar after meals. When you know how much carbohydrate you will eat, you can program extra units, or boluses, of insulin to cover your meals.

You figure out how much insulin to use based on your own insulin-to-carbohydrate ratio. This ratio may be different from one person to another, and even your own ratio may change over time. You and your doctor will calculate the ratio by recording the food you eat and testing your blood sugar after meals.

Test Your Knowledge

Carbohydrate counting helps me know how much insulin I need to take at meals.


To count carbohydrate grams at a meal, you need to know how much carbohydrate is in each type of food, whether it is a slice of bread, a bowl of lettuce, or a tablespoon of salad dressing. Fortunately, nearly all packaged foods have labels that tell you how much total carbohydrate is in a single serving. And you can get carbohydrate guides from diabetes educators and the American Diabetes Association.

To calculate the carbohydrate in food that is not packaged, you will need to know standard portions of carbohydrate foods. Each serving size or standard portion contains about 15 grams of carbohydrate.

When you know the number of grams of carbohydrate in a meal, you can figure out how many units of insulin to take based on your personal insulin-to-carbohydrate ratio.

For example: Your doctor may recommend that you take 1 unit of rapid-acting insulin for every 10 to 15 grams of carbohydrate you eat. So if your meal contains 50 grams of carbohydrate, and if your doctor has decided you need 1 unit of insulin for every 10 grams of carbohydrate, you would need 5 units of insulin to keep your post-meal blood sugar from rising above your target level.

Your insulin-to-carbohydrate ratio may change over time. In some people it will differ from one meal to another. You might take 1 unit of insulin for every 10 grams of carbohydrate for lunch but take 1 unit for every 15 grams at dinner. Keep the following in mind when counting carbohydrate grams:

  • Portion control is important. If a package says it contains two servings and you eat the whole package, you need to double the number of grams of carbohydrate listed for one serving.
  • Protein, fat, and fiber do not raise blood sugar very much. If you eat a lot of these nutrients in a meal, carbohydrate will convert to glucose more slowly than it would with a meal containing a small amount of protein, fat, and fiber.
  • Exercise affects blood sugar, allowing you to use less insulin than you would if you were not exercising. Keep in mind that timing makes a difference. If you exercise within 1 hour of a meal, your body may need less insulin for that meal than it would if you exercised 3 hours after the meal.

By keeping track of what you eat and testing your blood sugar after meals and exercise, you can learn to estimate the effect of protein, fat, fiber, and exercise on the amount of insulin you need.

Count carbohydrate grams and eat a balanced diet by:

  • Talking with a registered dietitian. He or she can help you plan the amount of carbohydrate to include in each meal and snack.
  • Measuring your food portions. You won't always have to measure your food, but it may be helpful when you are first learning what makes up a standard portion.
  • Counting either grams or servings of carbohydrate. A registered dietitian will help you plan how much carbohydrate, including sweets, to have in each of your meals and snacks.
  • Eating standard portions of foods that contain protein. Foods that contain protein (meat and cheese) are an important part of a balanced diet.
  • Limiting saturated fats. A balanced diet includes a limited amount of healthy fat. Talk with a registered dietitian about how much fat you need in your diet.

Other helpful suggestions

  • Read food labelsClick here to see an illustration. for carbohydrate content. Be careful to consider the serving size on the package.
  • Check your blood sugar level. If you do this before and 1 hour after a meal, you will be able to see how the food you eat affects your blood sugar level.
  • Record what you eat and your blood sugar results in a food recordClick here to view a form.(What is a PDF document?). At each regular visit with your registered dietitian or certified diabetes educator, or whenever you think your meal plan needs adjusting, you can review your food record.
  • Get more help. The American Diabetes Association offers booklets to help people learn how to count carbohydrate grams in their diet, to measure and weigh food, and to read food labels. But you will still need to talk with a registered dietitian to establish a plan that fits your needs.

Test Your Knowledge

I can eat only a certain amount of carbohydrate at one sitting, or my blood sugar will be too high.


Calculate the carbohydrate content in the following breakfast. Use the information in the "carbohydrate foods" and "foods that contain protein" links to calculate the carbohydrate. The breakfast includes 2 eggs, 1 cup of milk, 1 slice of toast, and 2 teaspoons of margarine.

30 grams of carbohydrate
35 grams of carbohydrate

Now that you have read this information, you are ready to plan regular meals and snacks and calculate the amount of carbohydrate in your diet.

Talk with your diabetes specialist (doctor or other health professional, registered dietitian, or certified diabetes educator). If you have questions about this information, take it with you when you visit your diabetes specialist.

If you need help with carbohydrate counting or meal planning, see a registered dietitian.

If you would like more information on meal planning for people who have diabetes, the following resources are available:


Academy of Nutrition and Dietetics
120 South Riverside Plaza
Suite 2000
Chicago, IL 60606-6995
Phone: 1-800-877-0877
Email: [email protected]
Web Address:

The Academy of Nutrition and Dietetics sets standards for all types of prescribed diets. The organization produces a variety of consumer information, including videos. This group will help you find a registered dietitian in your area who provides nutrition counseling.

American Diabetes Association (ADA)
1701 North Beauregard Street
Alexandria, VA 22311
Phone: 1-800-DIABETES (1-800-342-2383)
Email: [email protected]
Web Address:

The American Diabetes Association (ADA) is a national organization for health professionals and consumers. Almost every state has a local office. ADA sets the standards for the care of people with diabetes. Its focus is on research for the prevention and treatment of all types of diabetes. ADA provides patient and professional education mainly through its publications, which include the monthly magazine Diabetes Forecast, books, brochures, cookbooks and meal planning guides, and pamphlets. ADA also provides information for parents about caring for a child with diabetes.

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Other Works Consulted

  • American Diabetes Association (2008). Nutrition recommendations and interventions for diabetes. Diabetes Care, 31(Suppl 1): S61–S78.

  • American Diabetes Association (2013). Standards of medical care in diabetes—2013. Diabetes Care, 36(Suppl 1): S11–S66.

  • Campbell AP, Beaser RS (2010). Medical nutrition therapy. In RS Beaser, ed., Joslin's Diabetes Deskbook: A Guide for Primary Care Providers, 2nd ed., pp. 91–136. Boston: Joslin Diabetes Center.

ByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerRhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator
Last RevisedOctober 24, 2012

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