Diabetes and carbohydrates: What you need to know

Understanding the relationship between carbohydrates and diabetes management can help you recognize the effects of dietary choices on your blood sugar levels.  “Carb counting” or tracking the type, amount, and timing of carbohydrate intake can help you manage your metabolic control in the long run.¹ 

Carbohydrates, or carbs, may significantly impact diabetes management.² When you consume foods or drinks containing carbs, your body breaks them down into glucose, which raises the glucose level in your blood. This glucose serves as fuel to keep you energized.

After your body breaks down carbs into glucose, your pancreas releases insulin to help your cells absorb that glucose.²  If you're living with diabetes, this process is disrupted. In type 1 diabetes, the pancreas produces little or no insulin. In type 2 diabetes, the body doesn’t use insulin properly, and the pancreas may not produce enough. Combined with insulin resistance, this can lead to a build-up of glucose in the bloodstream.

Hyperglycemia, or high blood glucose levels, can occur when there isn't enough insulin in the body to promote the transport of glucose into cells or when cells don't respond effectively to the insulin, leaving excess glucose in the blood. Hypoglycemia , or low blood glucose levels, can result from insufficient carbohydrate intake or an imbalance in medications.³

To effectively manage your diabetes, it is crucial to achieve a balance in the carbs you consume.¹ If you have a target number of carbs to eat at each meal or snack, accurately estimating carbohydrates can help you keep your numbers within your target range.⁴

Keep in mind that these carb and blood glucose level targets aren't the same for everyone. What works for one person may affect another person's blood sugar levels differently. Discuss your ideal blood sugar levels and diet with your healthcare provider.

Carbohydrates can be classified into three main types: sugars, starches, and fibers.⁵ They are made up of sugar molecules, which are classified as simple carbohydrates or complex carbohydrates. Carbohydrates are not only important as an energy source but can also have a beneficial effect on overall health.⁶

Simple carbohydrates 

Simple carbohydrates, also known as simple sugars, are composed of sugars that have a basic chemical structure of one or two sugars.⁷ Single sugars (monosaccharides) include fructose and glucose, while double sugars (disaccharides) are sucrose, maltose, and lactose. 

Simple carbohydrates are often referred to as fast-acting carbs because they quickly convert into energy due to their basic chemical structure, resulting in a rapid increase in blood glucose levels.^7,8 

Complex carbohydrates

Complex carbohydrates, like fiber and starches, are made up of three or more sugars.⁷ These are called polysaccharides and can be found in grains, fruits, vegetables, and legumes. Complex carbohydrates are often called “slow-acting carbs” since they take longer to break down and don’t immediately affect blood sugar levels.⁸

It isn’t enough to just say that carbohydrates are simple or complex; you should also think about how they affect blood sugar and chronic illnesses.⁶ The glycemic index and glycemic load were developed to provide a more comprehensive understanding of the impact of carbohydrate-rich foods.⁹ 

Learn more about the different types of carbohydrates here.

Keeping track of the total grams of carbohydrates consumed is critical for controlling blood sugar levels.¹

At first, carb counting can be a little challenging. Foods with multiple ingredients make it hard to calculate totals, and official serving sizes often have no relationship to the servings people consume.

It can be easy to get overwhelmed by how many “healthy” foods are high in carbs and how many “unhealthy” foods aren’t. Remember that making small changes and sticking to them can have huge benefits.¹⁰

While there are several ways to count carbs, it’s really about personal preference. The best carb-counting method is one that addresses your personal, medical, and lifestyle needs. Talk to your healthcare team or seek the support of a registered dietitian, nutritionist, or Certified Diabetes Care and Education Specialist to determine what is best for you.

When it comes to actual carb counting, it’s important to include dairy products, fruits, and vegetables, along with grains and sweets. Approximately 15 grams of carbohydrates can be found in:¹¹

• Starches: 1 slice of bread, ⅓ cup of cooked pasta, ¾ cup of dry cereal, or 4-6 crackers
• Fruit: 1 small piece of fruit or ½ cup of fruit juice
• Milk: 1 cup of fat-free (skim) milk, or ¾ cup of yogurt
• Desserts: 2 small cookies or ½ cup of ice cream

Regardless of your meal plan's total carbohydrate content, it's key to focus on high-quality, nutrient-dense, fiber-rich, minimally processed carbohydrates.¹²

Carb counting tips

• Read the label: Sometimes, the carb count is easy to find. Take a moment to double-check the nutrition label.
• Understand serving sizes: Measure breakfast cereal or weigh pasta before adding it to the pot to get a sense of the recommended serving sizes.
• Make a mental note: Once it’s clear how a  ¾ cup serving of cereal fits into a bowl, for example, it’ll be easier to make decisions without needing to use measuring tools.
• Try a hand: A fist can help guide what a cup of food looks like. A cupped hand is approximately half a cup, whereas the palm measures about 85 to 115 grams, or 3 to 4 ounces.
• Use an app: Websites and apps can help by offering complete nutritional information.
• Glycemic Index/Load: You can further enhance your carb counting by considering the glycemic index and load of the foods you consume.

The glycemic index (GI) is a method for categorizing carbohydrate foods based on how quickly they are absorbed by the body and their impact on blood sugar levels.⁹ Foods ranked less than 55 are considered low glycemic index, foods ranked 56-75 are considered moderate, and foods ranked 76 and 100 are considered high.

• Low-glycemic index foods are absorbed more slowly, which reduces both the glycemic response and the corresponding insulin release.
• High-glycemic index foods are quickly absorbed and raise blood sugar levels more rapidly.⁹

A food's glycemic index is influenced by several factors, including its form, the way it is combined in a meal, cooking time, acidity, protein and fat content, and soluble fiber. All of these factors together influence how food impacts blood sugar levels.⁹

However, the glycemic index alone doesn’t fully reflect a food’s impact on your blood sugar levels. Other factors—such as how quickly glucose enters your bloodstream and the actual amount of glucose in a serving—also play a role, as GI doesn't take these into account.⁹ In this case, the glycemic load (GL) is useful for determining how a meal actually affects blood sugar levels. 

How to calculate glycemic load

Glycemic load is also measured on a scale, with values less than 10 considered low and those greater than 20 considered high.⁹ Multiply the glycemic index by the amount of carbs in a food and divide by 100 to get its glycemic load.

For example, one small apple has a glycemic index of 39 and 15 grams of carbohydrates, so to calculate its GL, you would multiply 39 by 15 and then divide by 100:

Some foods with a low glycemic index may have other components that are not necessarily healthy. Foods with added sugar or those that contain both saturated fat and carbohydrates (such as certain sweets) can still have a low glycemic index. GI and GL don’t account for other overall nutritional information about the food. For example, whole milk has a low GI and  GL value, but it's high in fats and calories.

The use of the glycemic index and glycemic load in meal planning for blood sugar control is a topic of debate, but it's considered a helpful tool for individuals with type 2 diabetes and weight concerns. ⁹

If you’re living with diabetes, counting carbs is an important part of managing blood glucose levels. This requires special attention to the carbohydrates section on nutrition labels. When it comes to carbs for people with diabetes, there’s no one rule for how much you can eat.  

Experts recommend consulting a doctor to develop an individualized meal plan that strikes the right balance of carbs and other nutrients tailored to your body’s specific needs.^1,14

It’s important to note that not all carbohydrates are equal. Here are a few different ways carb contents are addressed on nutrition labels.

Total carbohydrates

This line represents the total amount of carbs in one serving.¹⁵ This number is made up of both complex carbohydrates, like fiber and starch, and simple carbohydrates, like sugar.¹⁶

Dietary fiber

Some foods, like vegetables and many fruits, contain carbohydrates referred to as “dietary fiber.”¹ These complex carbohydrates slow the body’s absorption of sugar, which is very helpful for maintaining steady blood sugar levels. When it comes to fiber intake, aiming for approximately 35 grams per day is recommended. However, this amount can vary from person to person, so it's essential to monitor your blood glucose levels and consult with your healthcare provider for personalized advice on any changes.

Sugar alcohol

While sugar alcohols do add to the total carb and calorie count for a food serving, they are often included in “sugar-free” foods. Just like dietary fiber, sugar alcohols do not contribute to blood sugar as much as other forms of carbs can because they are not fully absorbed.¹⁸

Sugar

Sugar is the simplest kind of carbohydrate, which just means that it’s easiest for the body to absorb.⁵ As such, sugar has the most direct impact on blood sugar and is listed separately from total carbs to help anybody seeking to limit sugar, like people with diabetes, find foods that fit their diets.

Additional sugar:

Some newer food labels may include an additional line under “sugar” that lists any added ingredients beyond the natural sugars contained in the other ingredients in the food.¹⁵

With all of this in mind, choosing foods high in dietary fiber and low in sugar can help you maintain your ideal blood sugar range.¹ Everyone needs carbs, and it’s much easier to maintain a balanced diet when you choose the right carbs. Eat whole grains and foods high in dietary fiber, and consider the quality, quantity, and type of carbohydrates to help manage your blood sugar levels. Remember to monitor your blood glucose closely when you change your diet and discuss it with your healthcare provider for personalized advice.

Sources:

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16. Kristeen Cherney. Simple Carbohydrates vs. Complex Carbohydrates [Internet]. Healthline. 2023 May 23 [cited 2025 Jul 9]. Available from: https://www.healthline.com/health/food-nutrition/simple-carbohydrates-complex-carbohydrates  https://www.healthline.com/health/food-nutrition/simple-carbohydrates-c…
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19. Article on file.