8 Reasons You Might Feel Nauseous After a Workout — and How to Avoid It

1. Exercising right after you eat

When you exercise, blood flows away from your gut and toward the muscles you’re working. This shift lets your muscles get the oxygen and nutrients they need. But it’s also believed to be one of the main reasons exercise-induced gastrointestinal (GI) problems occur.

Less blood flow to your stomach and intestines can slow digestion and trigger nausea, vomiting, and diarrhea. If you eat right before a workout, your body won’t have enough time to fully digest your food. This can lead to stomach upset during or after your workout.

2. Eating slow-digesting foods before exercise

Well-timed preworkout nutrition powers your body, enhances your performance, and aids recovery. But it’s best to avoid certain foods before you exercise.

“Too much protein, fatty or greasy foods, and fiber take longer to digest,” said Elizabeth Ray, a dietitian and nutritionist. “So your body can’t break those ingredients down into nutrients you can use for energy by the time you exercise.”

These slow-digesting ingredients can make you feel too full or nauseous while exercising. Instead, choose preworkout snacks or small meals with lean protein and carbs, Ray said. 

Examples of these include:

• A banana with nut butter

• Oatmeal with berries

• A small, skinless grilled chicken breast with sweet potatoes

3. Drinking too much or too little water

Drinking water helps you stay hydrated and keeps your muscles working at their best while you exercise. And it offers a range of additional health benefits. 

“Water regulates your body temperature and supports healthy joints,” said Kelsey Sackmann, a dietitian and the founder of Kelsey and Cooper’s Kitchen. “It also helps your digestive system function properly.”

When you don’t get enough water, it can hurt your performance during exercise and cause symptoms like nausea and lightheadedness. Because of this, you might be tempted to guzzle water right before you work out. But drinking too much water can also contribute to nausea, Sackmann said.

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It’s easier to stay hydrated when you hydrate throughout your day Sackmann said. “Plan to drink water before, during, and after a workout, rather than loading everything up preworkout,” she suggested.

Consider drinking a beverage with electrolytes during your workout if you’re doing intense exercise or for more than an hour. This strategy will help you replace fluids lost through sweat, Sackmann added. If you’re working out in the heat, this is especially important.

4. Taking new medications or supplements

Medications and supplements can affect your workouts, whether you’re taking a new prescription or vitamin. That’s especially true if you take them on an empty stomach, said Ali Mesiwala, MD, a neurosurgeon and sports specialist at DISC Sports and Spine Center.

“A range of medications have known side effects, like nausea, that can interfere with your workouts,” he said.

Examples of medications and supplements that can cause exercise issues are: 

• Antibiotics

• Antidepressants

• Prescription and over-the-counter (OTC) pain medications, like opioids and ibuprofen 

• Mineral supplements and vitamins

• Some preworkout supplement blends, particularly if you dry scoop

Dr. Mesiwala recommended following the directions for your medication, including taking it with food if indicated.

5. Starting or stopping your workout abruptly

Dynamic warmups do more than prepare your muscles for a workout. This preworkout movement lets your entire body, including your gut, adjust to increased physical activity. 

“Suddenly going from zero to high-intensity interval training in a few seconds is likely to throw anyone off,” said Aaron Leventhal, a certified strength and conditioning specialist and the founder of Fit Studio. 

The same goes for cooldowns, which help your body return to its baseline. “Sudden, intense movement and abrupt stops are jarring to the body, including your stomach,” Leventhal said. “Add just a few minutes of cooldown time, even if you’re stopping in the middle of a workout.”

6. Working out too hard

In some parts of the fitness world, feeling sick after exercise is considered admirable. But that isn’t the sign of a successful workout.

“It’s a terrible idea to work out with such intensity that you have to vomit,” Dr. Mesiwala said. He added that nausea shouldn’t be treated like a normal part of working out. “Queasiness, dizziness, and other symptoms can signify overexertion,” he said.

Although exercise of any intensity can trigger nausea, strenuous workouts may increase your risk. That’s why exercise-induced GI distress — which can include nausea, vomiting, and diarrhea — is common among runners. If you’re regularly nauseated when you increase your exercise intensity, you’re probably trying to do too much too soon. And that can sabotage your progress instead of fueling it.

Certain types of exercise can also lead to postworkout nausea. Running or jumping on a trampoline, for example, involves a lot of bouncing and up-and-down movements that can make you queasy.

7. Exercising in the heat

Although your body is very efficient at regulating its temperature, exercising in the heat and humidity can throw off this balance, Dr. Mesiwala said. This is especially true if you’re dehydrated, hungover, or wearing clothes that don’t let your sweat evaporate.

“It’s the evaporation of sweat that cools you down, not just sweating itself,” Dr. Mesiwala said. “If sweat sticks to your body, that affects your temperature-regulation system.”

He added that nausea, dizziness, and muscle cramps are common symptoms of heat exhaustion. Other signs include headache, excessive sweating, rapid pulse, and thirst.

If you experience nausea while exercising outside or in other high-heat environments, Dr. Mesiwala suggested taking a break immediately and finding a cool resting spot, ideally in air conditioning. Often, nausea and other symptoms will resolve quickly. If they don’t, and especially if they get worse, you should seek medical care.

8. Wearing clothing that’s too tight

Form-fitting activewear can be supportive –– and make a fashion statement –– while you exercise. But if your clothing is too tight, it could also make you feel sick. 

Tight garments that press on or dig into your belly can cause digestive issues or worsen conditions, like gastroesophageal reflux disease (GERD), that cause nausea.

Tight clothing also traps heat, making it harder for your body to cool down. If you’re exercising in hot weather, you’re already at risk for heat exhaustion –– and the nausea that comes with it. Tight clothing can make an uncomfortable situation even worse. 

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