Food Timing and Exercise With Hypoglycemia

Throughout the day, your blood sugar levels fluctuate. Usually, you will not notice these changes unless they drop below the normal range. Then, you may start to feel a bit shaky, dizzy, and sweaty. This is known as hypoglycemia, or low blood sugar.

Although, hypoglycemia can occur at any time, it is sometimes brought on by exercise. When this occurs, it is due to lack of balance between your training volume, nutrition, temperature, altitude, and other external influences. Because hypoglycemia can be a rather common occurrence in people who exercise regularly, it is better to prevent hypoglycemia rather than treat it, and there are steps you can take to exercise safely.

What you eat and drink—and the timing of it—can help manage your blood sugar during exercise. Here we explain what to eat before and after a workout to help prevent hypoglycemia, whether you have diabetes or not.

What Is Hypoglycemia?

Blood sugar levels naturally fluctuate throughout the day and can be affected by food, beverages, exercise level and more. Some natural variation is normal, but when blood sugar drops below 70 mg/dL, it's considered hypoglycemia.

Low blood sugar triggers the hormone adrenaline, which causes rapid heart beat, sweating, and anxiety. If blood sugar continues to drop, it can result in more serious symptoms, such as blurred vision, coordination problems, and seizures. It's important to notice the early warning signs, monitor blood sugar levels carefully, and act quickly if hypoglycemia is detected.

Hypoglycemia can be treated quickly by taking 15 grams of a fast-acting sugar source, such as juice, soda, candies, or honey. Remember the "15-15 Rule." This rule suggests taking 15 grams of sugar, and check blood sugar levels after 15 minutes. If it's still below 70 mg/dL, take 15 grams of sugar again.

Hypoglycemia is common in people with type 1 diabetes, who may experience a few episodes of low blood sugar each week. It can also occur in people with type 2 diabetes who are taking insulin or certain medications.

While hypoglycemia is often related to diabetes, people can also have low blood sugar in the absence of diabetes. This condition is known as non-diabetic hypoglycemia and is considered rare.

Exercise-Induced Hypoglycemia

Sometimes, exercise will cause a spike in insulin, which can cause exercise-induced hypoglycemia (EIH), which simply means low blood sugar during or after exercise. People who do not have diabetes may get exercise-induced hyperinsulinemic hypoglycemia, and feel shaky, nervous, and dizzy. Like non-diabetic hypoglycemia, it's also considered a rare condition.

More commonly, EIH will happen to people who have diabetes. Exercise increases the need for glucose (sugar), which fuels muscles during activity. People are more likely to experience EIH if they take insulin, have low blood sugar from diabetes medication, or do an intense workout that uses up a lot of glucose.

"Exercise can improve your insulin sensitivity," says dietitian and certified diabetes educator Justine Chan, MHSc, RD, CDE, from Your Diabetes Dietitian.

This means the insulin works better and lowers blood sugar levels quicker than usual when you exercise. It's great for diabetes management, as long as hypoglycemia is managed too.

What to Eat Before a Workout

Eating on an empty stomach can trigger hypoglycemia, and should be avoided. Instead, eat a snack consisting of a protein and a carb beforehand.

"Since physical activity can lower your blood sugar, it is important to have a snack before working out," explains Vandana Sheth, RDN, CDCES, FAND, a Los Angeles-based registered dietitian and diabetes care specialist.

Sometimes hypoglycemia occurs because you didn't eat enough before exercise. Chan says that general (not diabetes) guidelines recommend a minimum of one gram of carbohydrate per kilogram of body weight to prevent hypoglycemia, 1 to 4 hours before any workout that will last 1 hour or more.

For people with type 1 diabetes, aim for 10 to 20 grams of glucose if blood sugars are less than <90mg/dl and 10 grams of glucose if blood sugars are 90 to 124mg/dl before a workout.  People with type 2 diabetes who take medication should check their blood sugar levels before exercise. If it's below 100 mg/dl, they should have 15 to 20 grams of carbohydrates to increase their blood glucose before exercise starts.

What to Eat After a Workout

Refueling after a workout is especially important if you are doing any type of endurance training, a competitive sport, or intense exercise over 60 minutes, Sheth says.

"A good post-workout option includes carbs, protein and some fat," she adds.

This combination will help your blood sugar level stay more stable. You can try a smoothie, apple with peanut butter, or berries and cottage cheese. It's also important to continue to check blood sugar levels.

"For people with type 1 diabetes, hypoglycemia can occur within 45 minutes of exercise, with its effect lasting up to 24 hours," says Chan.

If you are physically active in the late afternoon or evening, there's an increased risk of overnight hypoglycemia in people with type 1 diabetes. To reduce this risk, you may need to adjust your bedtime injected insulin dose or overnight basal insulin infusion rate. Speak with a healthcare provider for more specific guidelines.

How to Choose the Best Exercise With Hypoglycemia

Aerobic and resistance exercises are beneficial for diabetes management, but it is optimal to do both. You also may wonder if there is a better type of exercise if you are prone to hypoglycemia. In people with type 1 diabetes, high-intensity interval exercise is associated with less risk for hypoglycemia compared with continuous aerobic exercise.

"Strength training with high-rep workouts that raise your heart rate will lower blood sugar," says Sheth. "However, a strength training routine that is low-rep will most likely not cause a significant rise in your heart rate and may not affect your blood sugar as much."

Everyone’s blood sugar response to exercise is different, adds Chan. Monitoring blood sugars before, during, and after exercise will help better guide decisions around type of exercise, insulin dose adjustments, and carbohydrate intake for future sessions. Chan also suggests exercising in the morning, when insulin sensitivity is typically lower.  

A Word From Verywell

Hypoglycemia can be managed with some planning and foresight. What you eat before and after a workout can help keep blood sugar levels balanced and reduce the risk of EIH. If you often deal with hypoglycemia, work with a healthcare provider or registered dietitian to create a plan that works for you.