Diabetes: Counting Carbs if You Use Insulin
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.
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.
- Advanced carb counting takes into account the amount of fiber or sugar alcohols in a food. For example, if a food has 5 or more grams of fiber per serving, you can deduct half the amount of fiber from the total number of carbohydrate grams. A food that has 30 grams of carbohydrate and 8 grams of fiber would be counted as 26 grams of carbohydrate. If you use a rapid-acting insulin, you may want to consider sugar alcohols if there are more than 5 grams of sugar alcohol in the food. Divide the number of sugar alcohols in half and subtract that number from the total carbohydrate count.
- 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 (such as 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 labels 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 record (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.
Other Works Consulted
- American Diabetes Association (2013). Nutrition therapy recommendations for the management of adults with diabetes. Diabetes Care, 36(11): 3821–3842. DOI: 10.2337/dc13-2042. Accessed December 5, 2013.
- 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.
- Franz MJ (2012). Medical nutrition therapy for diabetes mellitus and hypoglycemia of nondiabetic origin. In LK Mahan et al., eds., Krause's Food and the Nutrition Care Process, 13th ed., pp. 675–710. St Louis: Saunders.
Last Revised: June 24, 2013
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