Does exercise lower blood sugar?

One in 3 adults in the U.S. has prediabetes, and 80% aren’t even aware of it. This means your blood glucose (sugar) levels are higher than normal but not yet at diabetes levels. Prediabetes increases your risk for more severe and life-threatening diseases, such as heart disease, stroke, and Type 2 diabetes. In fact, without intervention, many people with prediabetes will likely have diabetes within five years. 

A sedentary lifestyle and being overweight, especially around the mid-section, are major risk factors for prediabetes and some signs that you might already have high blood sugar levels. Regular physical activity is key to reducing long-term health risks, boosting overall well-being, improving insulin sensitivity, and keeping blood glucose levels healthy.

However, the relationship between exercise and blood sugar is complex. Read on to learn expert tips on the best activities for glycemic control, how the timing of your meals and workouts can affect your blood glucose levels, and strategies for safely managing your blood sugar with exercise.

RELATED: What are normal blood sugar levels? 

How does exercise help lower blood sugar?

High blood glucose levels can have serious consequences for people with prediabetes or diabetes. One of the benefits of exercise is that it can quickly bring blood glucose down to a safer level, says Saurabh Sethi, MD, a board-certified internal medicine physician in the San Francisco Bay Area. 

Your muscles require energy to work, and glucose is the body’s primary energy source, so simply put, exercising uses the glucose in your system, lowering the glucose levels in your body. There are a few fundamental mechanisms at work when you exercise that improve your blood sugar:

• Exercise increases muscle cells’ insulin sensitivity, enabling them to work better with insulin to process glucose during and after exercise.

• When your muscles contract during exercise, your cells are able to take up glucose and use it for energy, whether insulin is available or not. 

“When you work out, your muscles need energy, so they start using up the glucose in your bloodstream,” he says. This typically decreases blood sugar levels during exercise and immediately afterward, as well as up to 24 hours after exercise

How much can exercise lower blood sugar? 

The amount that exercise can lower blood sugar varies from person to person, says Dr. Sethi. “It depends on factors like how intense and how long one exercises, how fit the individual is, and their body’s sensitivity to insulin.” In general, the longer you exercise, the longer it will reduce your body’s glucose levels. 

However, the effects of exercise on blood glucose levels are short term—that is, one exercise session will immediately improve blood glucose by making the body more sensitive to insulin for an immediate duration. According to William Dixon, MD, co-founder of Signos, a continuous glucose monitoring system, one session of exercise can lower blood glucose for up to 24 hours or more.

Can exercise stabilize blood sugar in the long-term?

While the immediate effects of one workout are short term, research shows that regular moderate-intensity exercise also helps to lower blood sugar levels over time.

One tool that individuals and healthcare providers use to show changes in their blood sugar levels over time is an A1C blood test, which assesses how much sugar has attached itself to your hemoglobin over the previous three months. Having higher A1C levels is associated with diabetes complications, so if you have prediabetes or diabetes, it’s important to work with your healthcare team to manage your A1C goals. 

Does exercise lower A1C levels?

“Regular exercise can help bring down A1C levels,” Dr. Sethi says. When a patient “makes exercise a habit, it improves how the body responds to insulin, which helps to control blood sugar better and eventually leads to lower A1C levels.”

Dr. Dixon cites a study published in the journal Diabetes Therapy, which found that resistance training lowered blood sugar over the long-term—reducing A1C levels by 0.5% and increasing muscle strength by 38% in people older than 60. With consistency, he says, you will be able to see the improvements in an improved A1C.   

Is all exercise good for lowering blood sugar? 

Patients should be aware that in some cases, when exercise is too strenuous, or done on an empty stomach, it can cause blood sugar levels to spike temporarily. 

“How exercise affects [one’s] glucose depends on the type of exercise, when and what you’ve eaten, and potentially other factors,” Dr. Dixon explains. 

In particular, high-intensity exercise such as sprinting and heavy weightlifting can cause the body to produce stress hormones such as adrenaline. These can raise blood glucose levels by inducing the liver to release glucose, according to the American Diabetes Association (ADA). 

However, this is only a temporary response, and if you don’t have diabetes, this shouldn’t be too much of a cause for concern.

If you do have diabetes, you should develop your exercise regimen under your healthcare provider’s guidance. They will likely recommend you check your blood glucose levels before and after exercise to avoid any dangerous spikes or dips.

While exercise can lower your blood sugar, you can also make it drop too fast if you’re not careful. You want to avoid low blood sugar, also known as hypoglycemia, just as much as you want to avoid high blood sugar. This can sometimes happen if you’ve gone too long without eating before exercise.

And while exercise can quickly raise or lower blood sugar levels, the goal for most patients is to maintain it at a consistently healthy level and avoid potentially harmful spikes and dips.

RELATED: Blood sugar charts by age, risk, and test type

What types of exercise are best for blood sugar control?

For the best health benefits, healthcare providers generally recommend at least 150 minutes of exercise a week. To stabilize blood sugar, stick to moderate-intensity aerobic exercise that raises the heart rate without causing stress.  

Experts also suggest resistance and circuit training with light weights or body weight exercises that involve many repetitions to improve insulin sensitivity in muscles, which makes them more effective at using glucose for energy over time.

For best health results, most healthcare providers recommend a combination of the two types of exercise: aerobic and resistance.

The following exercises could help keep blood sugar levels in check:

• Brisk walking 
• Resistance or weight training with many reps and light weights
• Yoga
• Biking 
• Jogging or running
• Gardening
• Aerobic exercise

It’s important to talk to your healthcare provider to develop a plan that combines cardio and weights in a way that suits your individual needs and accounts for any existing health conditions you may have. 

When is the best time to exercise for blood sugar control?

If you are looking to get the most impact on your blood sugar out of your exercise, there are a few times that you should consider working out.

After 8 a.m. 

According to the ADA, if you have a natural rise in blood sugar between 4 a.m. and 8 a.m, this is known as the “dawn phenomenon,” and it can result in higher levels during early morning exercise.

In the afternoons

A recent study in the journal Diabetes Care found that people with Type 2 diabetes who did moderate exercise in the afternoon as opposed to other times of the day had more stable glycemic levels over four years. They were also the most likely of the study population to be able to stop taking glucose-lowering medications.

After eating

Your blood glucose levels are affected by what you’ve eaten recently, so coordinating your exercise schedule with your meals is a good way to keep them in check.

“A short walk 10-15 minutes after eating a carbohydrate-filled snack will likely prevent one’s glucose from rising as high as it might otherwise,” Dr. Dixon says. “The same walk on an empty stomach might increase one’s blood sugar a bit as the body makes energy for the muscles to use.” 

When your healthcare provider recommends

Blood sugar reactions can vary, and each individual is different. “Some people find that exercising in the morning helps them keep their blood sugar levels in check throughout the day,” Dr. Sethi says. “But others might benefit more from exercising after meals to prevent any [blood sugar] spikes.” 

For those with diabetes, it’s essential to keep a close eye on blood sugar levels and work with a healthcare team to find the timing that works best.  

Whenever you can

Ultimately, any time is better than not exercising at all. Prioritizing exercise whenever you can schedule it is more important than getting the timing just right, emphasizes Dr. Dixon.  

Takeaway

Exercise is an essential component of blood sugar control and diabetes management or prevention. Healthcare providers recommend regular light to moderate workouts and a combination of aerobic and resistance training to lower your blood sugar in the short and long term. The type of exercise you do and coordinating your exercise and meal schedules can also influence your blood sugar. However, individual glucose levels and responses vary from patient to patient, so speak with your healthcare provider for advice before undertaking any exercise routine.