Carb Counting on Mealtime Insulin

Medically Reviewed By William C. Lloyd III, MD, FACS
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Lately, it seems like carbohydrate (carb) counting is all the rage when it comes to losing weight and staying healthy. Carb counting is exactly what you think it is—counting the number of carbohydrates you eat at a given meal.

It may be a weight loss technique, but carb counting is also beneficial for people living with diabetes, especially those who take insulin at mealtimes. In many cases, carb counting helps diabetics achieve better blood sugar control, because knowing the amount of carbs eaten allows diabetics to more accurately dose their mealtime insulin.

Plus, if you use mealtime insulin, counting carbs may help you learn which types of foods have a greater impact on your blood sugar. Before starting any type of carb counting regimen, it’s important to discuss your plan with your doctor. Your doctor will help you determine your initial dose of mealtime insulin and can recommend adjustments based on your results.

Carbohydrates: The Basics

Carbohydrates are one of the main nutrients you need to stay healthy, along with fats and proteins. There are many dietary sources of healthy carbohydrates, including whole grains, vegetables, and fruits. These healthy carbs provide your body with nutrients and energy. You can also find carbs in some unhealthy foods, such as those with added sugars. While still providing energy, these types of products generally don’t provide any useful nutrients.

All carbs contain sugars and starchy components. Every time you eat carbohydrates, your body breaks down the starches and sugars into glucose, which is the singular form of sugar your body uses for energy. A naturally-occuring hormone called insulin plays a key role during this process. After the carbs you’ve eaten are broken down into glucose, that glucose remains in the bloodstream. Insulin helps send glucose out of the bloodstream and into the tissues of your body to be used for energy. This way, your body gets the energy source it needs, and the level of glucose in your blood isn’t too high or too low—problems which can have serious consequences for your health.

When you have diabetes, your body is unable to use insulin effectively or it doesn’t make enough of it, resulting in high blood glucose levels. That’s why many diabetics take medications to help the body use insulin more efficiently or make more. Eventually, diabetics may need to give themselves insulin injections to replace the insulin their bodies aren’t making.

Your Carb Counting Plan

Your doctor may recommend carb counting as a way to help manage your blood glucose levels and reduce (and more accurately dose) the amount of insulin you take at each meal. If you take mealtime insulin, you’ll adjust your dosage depending on how many carbs you’ll consume. In essence, you need to take enough insulin to help process the carbs you eat. To begin, you should speak with your doctor or a registered dietitian to create a meal plan. Your personalized plan specifies how many grams of carbs you’ll eat at each meal throughout the day. Knowing how many grams to consume helps you plan your mealtime insulin dose accordingly.

Next, work with your doctor to learn how many carbohydrates are included in the foods you commonly consume. It’s important to be able to estimate the total amount of carbs in each food item you eat so that your mealtime insulin dose is calculated correctly. This skill also helps you determine how many total carbs you consume at each meal.

To stick to your meal plan, you may use certain items, like food scales or measuring cups, to weigh out food items into single portions. Controlling your portion size limits the amount of carbs you consume.

Your Mealtime Insulin Dose

Once your meal plan is created and you know how many carbs you consume in each meal, you can use this information to calculate your mealtime insulin dose. In general, one unit of short-acting insulin covers up to 15 grams of carbohydrates. However, your personal insulin needs may differ depending on other factors, like your sensitivity to insulin, your activity level, and your weight.

If your doctor determines one unit of insulin will cover 15 grams of carbs, you can calculate your mealtime insulin dose using simple math. For example, assume you eat 60 total grams of carbohydrates during a meal. Divide 60 by 15 to get four units of short-acting insulin needed to cover the amount of carbs in the meal. In this example, you would need to inject four units of insulin to keep your blood glucose levels stable after your meal.

Before adjusting your mealtime insulin dose, it’s very important to speak with your doctor about your plan. Each person’s insulin needs are different, and, for you, one unit of insulin may cover a different amount of carbohydrates in your meals. Carb counting may offer you more choice and flexibility when planning your meals while also helping you reduce the amount of insulin you depend on to stay healthy. Working with your doctor is the best way to count carbs effectively while making sure your diabetes is managed.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 29
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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