Common Causes of Blood Sugar Spikes

Medically Reviewed by Michael Dansinger, MD on December 06, 2020

Because you have type 2 diabetes, you know it’s a must to keep your blood sugar levels under control. But do you know what makes them spike?

Check this list of common culprits, plus ways to help you stay healthy and feel great.

1. Your Diet

Watch what you eat since that's one of the most important things you can do to control your blood sugar, also called blood glucose.

That’s because of the impact that carbohydrates -- the sugars and starches in foods -- can have.

It’s fine to eat them in moderation. But choices that have too many carbs can cause your blood sugar to soar -- white rice, pasta, and highly processed or fried foods are examples. Some fruits are high in sugar, such as bananas. It’s OK to have fruit, just not too much.

Choose good carbs, like whole-grain bread and cereal, unprocessed grains such as barley or quinoa, beans, whole wheat pasta, brown rice, fruit, yogurt, and vegetables.

Fiber helps because it lowers blood sugar. Good choices are whole grains, fruits that are lower in sugar (apples and blueberries), veggies, and legumes.

2. Too Little Sleep

Not getting enough rest does more than make you groggy. It also affects how well your body can control and break down blood sugar.

In one study, researchers asked healthy adults to sleep just 4 hours a night for 6 days. At the end of the study, their bodies’ ability to break down glucose was 40% lower on average. Why? Doctors believe that when you enter deep sleep, your nervous system slows down and your brain uses less blood sugar.

Get your shut-eye. Remember all the things that help: Stick to a regular schedule, don't use your phone or tablet close to bedtime, and relax before you hit the hay.

3. Too Much (or Too Little) Exercise

Even a mild workout, like walking or doing light housework, can lower your blood sugar and improve how your body responds to insulin.

When you don’t move around enough, your glucose levels can rise. Too much exercise can have the same effect. Tough activities, like bench-pressing weights, or competitive ones, like running a race, can raise your blood sugar.

That doesn’t mean you can’t sweat it out. Exercise is one of the best things you can do for your whole body. But ask your doctor what changes you may need to make in your treatment plan to keep your blood sugar in the right range.

4. Stress

This is your fight-or-flight response. It prompts your body to act like it’s under attack.

When this happens, your hormone levels go up. Your body burns its stored energy sources -- glucose and fat -- to meet the threat. When you have diabetes, insulin can’t break through the cells to break down the glucose, and your levels rise.

Stress can also cause blood sugar to rise indirectly. You may be less likely to take care of yourself by eating right, exercising, or taking your medicine when you’re stressed out.

Learn to relax. Try meditation, yoga, or massage.

5. Some Medications

You know that insulin can bring your blood sugar down. But if you miss a dose or take the wrong dose of your medicine, you could cause your levels to spike. Some drugs, such as corticosteroids, can have the same effect. Other meds that could raise your glucose include:

  • Diuretics (“water pills”)
  • Drugs used to treat depression
  • Blood pressure medicines

If you’re on any of these medicines and you notice your blood sugar is high, talk to your doctor. They may adjust your diet or medications.

6. Not Brushing and Flossing

If you have diabetes, you’re more likely to get gum disease. And serious gum disease can make it harder to keep your blood sugar under control. Like all infections, it may cause your glucose to rise. That, in turn, can make other infections more likely. Make sure you not only brush and floss your teeth but also rinse with an antiseptic mouthwash daily.

Keep up with your dentist visits, work on managing your blood sugar, and, if you have gum disease, treat it -- and any other infection in any part of your body -- ASAP.

7. Smoking

If you light up, you raise your chances of getting diabetes. If you already have diabetes, you’re more likely to have trouble finding the right dose of insulin and controlling your blood sugar. Smoking makes it harder to keep your blood sugar levels down.

The lesson here: If you smoke, quit.

Blood sugar levels go up from time to time. But knowing what can cause these spikes can help you control them -- and avoid health problems down the line.

WebMD Medical Reference


SOURCES: “Carbohydrates and Diabetes.”

Cleveland Clinic: “Good Carbs.”

National Sleep Foundation: “Sleep Longer to Lower Blood Glucose Levels.”

University of California, San Francisco: “Exercise & Blood Sugar.”

Joslin Diabetes Center: “Why Can’t I Exercise With Ketones?”

BD Diabetes Learning Center: “Common Medications That Can Cause High Blood Sugar.”

NHS Choices: “Hyperglycaemia (high blood sugar).”

American Diabetes Association: “Diabetes and Oral Health Problems,” “Stress.”

American Dental Association: “Diabetes and Your Smile.”

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