What Are Carbs? And What to Know About Carbs and Blood Sugar

Carbohydrates (carbs) are an important part of a healthy diet, and keeping track of them is crucial for people with diabetes. 

You may wonder if it is possible to include carbs in a healthy diet, especially if you’re trying to control your blood sugar levels. (Spoiler alert: The answer is yes.) But it’s important to understand how each type of carb affects your body. 

What are carbohydrates?

Carbs are a macronutrient and the primary energy source for your body (along with proteins and fats). They include starches, sugars, and fiber. For the most part, fibers and starch are complex carbs, while sugars are simple carbs. Some familiar carbs are:

• Grains

• Pasta

• Bread

• Milk 

• Fruits

• Sweets

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Do carbs turn into sugar? ​​

In short, yes. When you eat carbs, your body breaks them down into glucose (sugar) and uses them for energy. Carbs first get broken down by the saliva in your mouth and then by your gut until they’re completely broken down into glucose. Once the glucose gets into your blood, it’s known as your “blood sugar.” 

Carbs affect your blood sugar level more than protein or fats do. When the body senses a large amount of glucose rushing into the blood, the pancreas releases a hormone called insulin to tell the cells to take in the glucose, keeping blood sugar levels from getting too high.  

However, some people’s cells may not respond well to insulin, including people with prediabetes or Type 2 diabetes. On the other hand, sometimes the pancreas can’t make enough insulin, and people need insulin injections instead. This is the case with people who have Type 1 diabetes and some people with Type 2 diabetes or gestational diabetes. For people with these conditions, it’s particularly helpful to know what food choices to make to keep blood sugar levels under control.

Is sugar a carb? ​​

Yes, sugar is one of the main types of carbs. Some foods contain naturally occuring sugars, like fructose (found in fruits) and lactose (from milk). But some foods have added sugars, which are incorporated during processing. These include:

• White sugar

• Brown sugar

• High fructose corn syrup

• Natural sweeteners, like honey and maple syrup

• Certain sugar alcohols, like xylitol and maltitol

Carbs can be classified into two main categories based on the number of sugars they contain: simple carbs and complex carbs. Regular or table sugar is a simple carb, while fiber and starch are more complex carbs. We’ll go into more detail below.

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Simple carbs vs. complex carbs ​​

On a basic level, simple carbs are those that are quickly broken down by the body. Complex carbs take longer to break down. 

The speed at which a carbohydrate moves through your digestive system has a significant impact on your blood sugar. Simple carbs raise your blood sugar more quickly. Complex carbs lead to a more steady increase in blood sugar. 

Because of this, the general recommendation is to eat mostly complex carbs and limit simple carbs. But not all simple carbs raise blood sugar faster than all complex carbs (more on this later). 

Let’s dig a little deeper below.

What are simple carbs?

Simple carbs include natural sugars and the processed sugars that are added to foods like cakes, breakfast cereals, and ultra-processed foods. 

Examples of common foods containing simple carbs include:

• Fruit

• Honey

• Fruit juices and sugar-sweetened beverages

• Milk

• Ice cream

• Most baked goods

• Most breakfast cereals

Keep in mind that not all foods that contain simple carbs raise your blood sugar equally. For example, because fruit contains fiber, you’ll absorb its sugar more slowly, causing a less dramatic rise in blood glucose levels than, say, if you drank a sugary soda.

What are complex carbs?

Complex carbs include starches and fiber and are usually found in whole or unprocessed foods. 

Some examples of foods that contain complex carbs include:

• Whole grains such as quinoa, brown rice, and millet

• Starchy vegetables such as sweet potato and corn

• Non-starchy vegetables such as zucchini, okra, and jicama 

• Beans and legumes such as chickpeas and lentils

Many foods that contain complex carbs also contain important nutrients such as vitamins and minerals. Although fiber has no nutritional value itself, it is essential for:

• Maintaining healthy bacteria in the large intestines

• Promoting regular bowel function 

• Lowering cholesterol

• Preventing sharp increases in blood sugar

• Helping you feel full and satisfied after a meal

Is starch a carb?

Yes — specifically, it’s a complex carb. But keep in mind that complex carbs can refer to any starches, including “refined” starches found in some foods. 

Refined starches, like white flour or white rice, are broken down more quickly than unprocessed starches and can cause a fast rise in blood sugar. It’s best to limit foods that contain refined starches, as they are also low in nutrients. Some examples include:

• White bread

• Most baked desserts, including cakes, doughnuts, and cookies

• Sweetened cereals

• Bagels

Apart from knowing the differences between simple carbs and complex carbs, there are other tools that can give you an idea of how a carb can affect your blood sugar. 

What is the glycemic index?

The glycemic index (GI) gives us a way to measure how different carbs affect our blood sugar levels. 

GI is a value that shows how fast your blood sugar may rise when you eat a food compared to eating pure glucose, which has a GI value of 100. Foods with a higher rating may cause your blood sugar to rise faster than foods with a lower glycemic index score.  

Low GI: 1-55

Medium GI: 56-69

High GI: 70 and higher

The chart below shows the GI values of some common foods:

Keep in mind, how you prepare a food can also impact its GI. For example, preparing foods with extra-virgin olive oil can help lower their GI. Making pasta? One study found that cooking pasta al dente (firm and not over-cooked) can lower its GI.

What is glycemic load?

The glycemic load (GL) of a food is different from its GI — and understanding both is important. While knowing the GI of a food will tell you the rate at which it will raise your blood sugar, it doesn’t tell you how high your blood sugar could go. That’s what GL tells you.

Low GL: 10 and lower

Medium GL: 11-19

High GL: 20 and higher

For example, watermelon and donuts have the same GI, which means the sugars they contain will make your blood sugar rise at about the same rate. But a serving of watermelon contains fewer carbs than the same amount of donut. So the watermelon has a lower GL. Carrots are another example of a high GI and low GL food. 

GI and GL don’t just affect diabetes. Eating a diet of high GI and GL foods has been associated with an increased risk of cardiovascular disease, and a low GI diet has been shown to lower cholesterol.

What are some options for balancing carbs?

It is important to note that while the GI and GL are useful tools to assess the effect of foods on blood sugar, there are several other factors to consider as well. For example, protein and fiber content in a specific food can affect blood sugar, and so can other foods that you consume at the same time. 

Sticking to balanced portions of fresh, non-processed foods, as opposed to processed and high-sugar foods, is an easy way to make sure you’re getting healthy carbohydrates. 

That said, both carb counting and the plate method are also useful for people looking for more precise ways to monitor their carb intake. 

Counting carbs

For people with diabetes, counting carbs simply involves figuring out how many grams of carbs are in a food and matching that with an appropriate dose of insulin. For foods that come in a package, you can figure out the amount of carbohydrates in a serving by looking at the nutrition facts label under “Total Carbohydrates.” You multiply that amount by the number of servings you’re having to find out how many grams of carbs you’re eating.  

For foods that do not come in a package, such as fruits and grains, there are apps and other sources of food data that can help you determine how many grams of carbs you’re eating. In diabetes meal planning, one serving of carbs is about 15 g.  

Below are some examples of about 15 g of carbs in a few common foods:

• ½ large banana

• ¾ cup blueberries

• ⅓ cup cooked rice or pasta

• 1 slice of toast

• ¼ large bagel

Precise carb counting is important for people with diabetes who are on mealtime insulin regimens. For everyone else, carb counting is a helpful tool to help you get an idea of how many carbs you’re eating. It might be a lot more than you think.

The plate method

The plate method is a tool that helps people with diabetes manage their blood sugar by creating balanced meals. Following the plate method can help keep your blood sugar stable and keep you full for longer. This approach emphasizes nutrient-rich foods, like non-starchy vegetables, whole grains, and legumes. It also helps you avoid refined grains and highly processed products.

The plate method can be just as effective as carb counting when taught by a diabetes professional.  

To learn more, reach out to your healthcare team and get connected with a registered dietitian or certified diabetes care and education specialist. Medical nutrition therapy (MNT) and diabetes self-management education and support (DSMES) are covered by most insurances for people with diabetes.    

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Written by:

Lindsay Boyers, CHNC

Lindsay Boyers, CHNC, is a functional nutritionist, licensed esthetician, writer, and editor with over a decade of experience in evidence-based health, wellness, and skincare writing.

Edited by:

Samvida Patel, MNSP, INHC

Samvida Patel, MNSP, INHC, is a health editor at GoodRx. She is a nutritionist and integrative nutrition health coach with over 8 years of experience in health communications.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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