Blood sugar, also known as blood glucose, comes from the food you eat. Your body digests some of the food you eat into sugar that then circulates in your bloodstream.

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Blood sugar is used for energy. Excess sugar in your blood gets stored in cells for later use.

Too much sugar in your blood can be harmful. Type 2 diabetes is a disease where you have higher levels of blood sugar than typical limits. Unmanaged diabetes can lead to problems with your heart, kidneys, eyes, and blood vessels.

The more you know about how eating affects blood sugar, the better you can protect yourself against diabetes. If you already have diabetes, it’s important to know how eating affects your blood sugar.

This article explains how what you eat affects your blood sugar and how to understand your blood sugar levels.

Your body breaks down everything you eat and absorbs the food in its different parts. These parts include:

The carbohydrates you consume turn into blood sugar. The more carbohydrates you eat, the higher the levels of sugar will be released into your body as you digest and absorb your food.

Carbohydrates in liquid form consumed by themselves absorb more quickly into your body than those in solid food. So, soda will cause a faster rise in blood sugar levels than a slice of pizza.

Fiber is one component of carbohydrates that isn’t converted into sugar. This is because it can’t be digested. Fiber is important for health, though.

Protein, fat, water, vitamins, and minerals don’t contain carbohydrates. Carbohydrates have the greatest effect on blood glucose levels.

If you have diabetes, carbohydrate intake is the most important part of your diet to consider when managing your blood sugar levels.

The foods that cause the biggest spike in your blood sugar are high in processed carbohydrates. These foods include:

  • white grain products, such as pasta, rice, and bread
  • cookies
  • cold processed cereals
  • sugared drinks

You don’t have to avoid these foods if you’re watching your carbohydrate intake. Instead, you’ll need to be careful about portion size and substitute with whole grains when possible. The more food you eat, the greater the sugar you’ll absorb.

Eating mixed meals is helpful. Protein, fat, and fiber help slow the digestion of carbohydrates. This will help reduce spikes in blood sugar after meals.

How often you eat during the day is also important. Keep your blood sugar levels consistent by eating every 3–5 hours. Three nutritious meals a day plus a couple of healthful snacks can usually keep your blood sugar steady.

If you have diabetes, your doctor may recommend the amount of carbohydrates you can have for meals and snacks. You may also work with a dietitian familiar with diabetes who can help plan your meals.

Your health, age, and activity level all play a part in setting your dietary guidelines.

Exercise can have a big effect on your blood sugar levels because blood sugar is used for energy. When you use your muscles, your cells absorb sugar from the blood for energy.

Depending on the intensity or duration of exercise, physical activity can help lower your blood sugar for many hours after you stop moving.

If you exercise regularly, the cells in your body may be more sensitive to insulin. This will help keep your blood sugar levels within typical ranges.

Insulin is an important hormone that helps regulate your blood sugar levels. The pancreas makes insulin. It helps manage your blood sugar levels by assisting the cells that absorb sugar from the bloodstream.

If you have type 1 diabetes, your body doesn’t make insulin. This means you have to inject insulin every day.

If diet and exercise aren’t enough to manage blood sugar, those with type 2 diabetes may be prescribed medications to help keep blood sugar levels within target ranges.

If you have type 2 diabetes, your body produces insulin but may not use it properly or produce enough of it. Your cells don’t respond to insulin, so more sugar keeps circulating.

Exercise can help the cells respond better and be more sensitive to insulin. The proper diet can also help you avoid spikes in blood sugar. This can help keep your pancreas functioning well since high blood sugar levels decrease pancreatic function.

If you have diabetes, the frequency of testing your blood glucose level depends on your treatment plan, so follow your doctor’s advice at the appropriate times.

Common times to check are in the morning, before and after meals, before and after exercise, at bedtime, and if you feel sick. Some people may not need to check their blood sugar daily.

What you eat and do for physical activity affects your blood sugar. But you cannot know their effect unless you test your blood sugar.

Blood glucose meters are used to test blood sugar levels so you can see if your levels are within the target range. Your doctor will also work with you on your individualized range.

Here are some frequently asked questions about eating and blood sugar levels.

What should your blood sugar level be after eating?

According to the British Heart Foundation, a person without diabetes should have a blood sugar level between 80 and 130 milligrams per deciliter (mg/dl) pre-meal and less than 180 mg/dl after eating.

Is 200 mg/dL blood sugar normal after eating?

Blood sugar greater than 100–125 mg/dL before meals and greater than 140–180 mg/dL 2 hours after meals is classified as prediabetes or glucose intolerance.

Carbohydrates are the component in food that affects blood sugar the most. However, carbohydrates are not the only component that provides calories. Foods also contain proteins and fats.

If you consume more calories than you burn in a day, your body will convert those calories into fat and store them.

The more weight you gain, the less sensitive your body becomes to insulin. As a result, your blood sugar levels can rise.

In general, you want to avoid or minimize your intake of sweetened beverages and foods that are highly processed, high in carbohydrates and unhealthy fat, and low in healthy nutrients.

For example, a brownie may have as many carbohydrates as a banana, but the fruit also has fiber, potassium, and vitamins your body needs. Brownies don’t have those benefits.

If you have diabetes or you’ve been told you have high blood sugar levels, talk with your doctor or a dietitian about what you can do to eat smarter and healthier.