Why do I feel nauseous after working out?

You’re midway through your run, but then you start to feel queasy. It’s unpleasant, sure. But you may be wondering, “Why do I feel nauseous after working out?” The good news is that most cases of post-workout nausea are not serious. During exercise, the body sends blood to major muscle groups, which reduces blood flow to abdominal organs. This can lead to nausea. Post-workout nausea may also stem from elevated blood pressure, poor hydration, or working out too soon after a meal.

Here’s everything you need to know about nausea after exercise, including common causes and management and prevention tips.

Is it normal to feel nauseous after working out? 

It is not uncommon to experience nausea after working out, according to Kayley Myers, MS, RDN, a registered dietitian nutritionist in Springfield, Missouri. “It is most common in long-distance runners and other endurance athletes,” adds Erin Nance, MD, board-certified orthopedic surgeon in New York City.

What causes nausea after working out?

Nausea after working out is common—but certainly unpleasant. Sometimes post-workout nausea also comes with dizziness, vomiting, or diarrhea. Below, Myers and Dr. Nance weigh in on common causes of nausea after high-intensity exercise.

1. Exercising too soon after eating

“Eating too close to a workout can increase your risk for nausea,” says Myers. “Because there is less blood flow to your stomach, it can take longer for your food to digest. 

Think of it this way: Less circulation in the digestive system slows overall food digestion and may cause gastrointestinal stress. If you still have food in your stomach at the beginning of a workout, that food is likely to stick around for longer, potentially sloshing around during activity and causing an upset stomach. In some cases, the nausea can even make you vomit.

2. Eating heavy, slow-digesting foods before a workout

Many athletes and fitness enthusiasts consume pre-workout supplements or snacks to fuel their sweat sessions. But not all snacks are created equal. “Eating heavy or spicy meals prior to a workout can cause indigestion and nausea,” Dr. Nance. Research suggests that eating fatty foods before a workout can also lead to nausea.

RELATED: Does exercise help with digestion?

3. Not hydrating properly

Most people are aware of the risk of dehydration during strenuous exercise. But Myers says both too little and too much fluid can make you feel nauseous after working out.

Proper hydration is vital for feeling and performing your best during a workout. However, that doesn’t mean you should chug a bottle of water before hitting the treadmill. Flooding your stomach with fluids can trigger reflux, vomiting, and nausea. Drinking water consistently throughout the day is better than trying to hydrate all at once.

“Overhydrating can throw off your sodium levels and also cause nausea,” Myers explains. Known as hyponatremia, overhydrating can also cause low blood pressure, headache, fatigue, and confusion. Overhydrating is rare, but serious. 

4. Low blood sugar

“Low blood sugar, also known as hypoglycemia, can cause nausea during or after a workout,” Myers says. “While this can happen to anyone, people who take diabetes medications like insulin are at higher risk.”

Hypoglycemia also causes side effects such as lightheadedness, dizziness, and rapid heart rate. Most healthcare professionals recommend treating mild low blood sugar with a portion of fast-acting carbohydrates such as glucose tablets, fruit juice, or even sugary candy. It is important to have some on hand when you exercise.

5. Heat exhaustion

Nausea is a warning sign of heat-related sickness, according to the Centers for Disease Control and Prevention (CDC). So if you feel nauseous after a hot yoga session or running in the midday sun, consider the possibility that your body might have overheated.

If your post-workout nausea is caused by heat exhaustion, you might also experience these other symptoms:

• Heavy sweating
• Cool, clammy skin
• Muscle cramps
• Weakness
• Headache
• Rapid or weak pulse

If you’re experiencing these symptoms after a strenuous workout, move to a cool location, start hydrating, and get help immediately if you begin to vomit.

Should I stop working out if I feel nauseous?

If you feel like you’re going to vomit during a workout, take a break and slowly sip water. Consider taking more time to warm up or starting with a lower-intensity workout next time.

“If the cause of the nausea is purely exercise-induced or a symptom of dehydration, the nausea should stop after a period of rest or rehydration,” says Dr. Nance. “Prolonged nausea (lasting more than one day) should be evaluated by a doctor to rule out causes related to your gallbladder, pancreas, or heart.”

Talk to your healthcare provider if you feel nauseous after every workout or even when performing non-strenuous activities. Dangerous conditions such as a heart attack can cause nausea, according to Dr. Nance, so it’s always best to get checked out if queasiness has become a constant companion.

How do I stop feeling nauseous after working out?

“Relief from post-workout nausea depends on the cause,” says Myers. “A good first step is to slow down or stop your workout.” Taking a break could allow your body to divert blood flow back to your GI tract and relieve nausea related to slow digestion. 

If your nausea is caused by dehydration, sipping on water or a sports drink should help you feel better quickly. 

If your nausea is related to low blood sugar, Myers recommends consuming 15 grams of carbohydrates every 15 minutes until your blood sugar is at or below 70 mg/dL. “It is important to talk to your doctor if you believe this may be the cause of your post-workout nausea,” she adds. 

Most cases of post-workout nausea should resolve with rest and hydration, according to Dr. Nance. If you’re still feeling nauseous 24 hours after exercising, consult a healthcare professional.

RELATED: Nausea relief medications and home remedies

Preventing nausea after working out 

If you feel nauseous after working out, the best thing you can do is rest in a cool environment and rehydrate until you feel better. But that doesn’t mean you should avoid exercise forever. Physical activity is an important part of overall wellness. 

Try these tips for preventing nausea after your next workout (though remember that the efficacy will depend on what is causing your nausea in the first place):

• Avoid full or heavy meals before exercise. Meals high in fat and fiber are best avoided before a workout, says Myers. Dr. Nance recommends waiting two hours after a big meal before exerting yourself. 
• Prioritize carbs in your pre-workout snack. Eat a snack with carbohydrates and protein one to four hours before your workout, recommends Myers. She suggests simple snacks such as fruit and yogurt, a bagel with peanut butter, or tuna with crackers. 
• Drink water regularly. “Make sure that you are well-hydrated prior to your workout,” Myers says. “This can help reduce the chances of becoming nauseous from dehydration after your workout.”
• Try electrolytes. “If you tend to sweat a lot or work out for more than one hour at a time, consider using an electrolyte sports drink to help replenish fluid, sodium, and glucose,” says Myers. 
• Vary exercise intensity. Exercise-induced vomiting and feeling nauseas after working out are more common with strenuous physical activity. Try lowering the intensity of your workout. This may decrease nausea after exercising—and you’ll still enjoy the surge of feel-good endorphins.
• Discuss blood sugar concerns. If you are experiencing consistently low blood sugar and do not have a diagnosis, discuss your symptoms and concerns with a healthcare professional. 

Exercise-induced nausea is common, but that doesn’t mean you have to suffer. Plan at least two hours between meals and workouts, stay hydrated throughout the day and pay careful attention to the severity and frequency of your post-workout nausea. 

If you’re concerned about low blood sugar or an underlying condition, talk to your healthcare provider. They can help you find a treatment that will allow you to continue enjoying exercise.