Why Do I Feel Sick After Working Out?

That moment mid-workout when your stomach suddenly drops or you get a lump in your throat and you think, am I about to be sick? Yeah, we've all been there.

Research shows gastrointestinal symptoms affect at least 20% of athletes, with some studies putting that figure closer to 70%. Symptoms can range from upper GI issues (nausea, reflux, burping, vomiting) to lower GI discomfort like cramps, gas or diarrhoea.

The most common causes are dehydration, training intensity, meal timing, overheating, and reduced blood flow to your digestive system. When you exercise, your body redirects blood to your muscles to deliver oxygen and nutrients where they're needed most, which means your gut takes a back seat. Totally normal, but that's what can sometimes cause the problems.

Plenty of factors play a role, including your age, sex, training history and level of fitness. But the good thing is that most causes are fixable. Here's where to start.

If you try the changes below and still can't shake it, it's worth checking in with your healthcare provider.

Timing your food around your workouts

What and when you eat before exercise makes more of a difference than most people realise. Food takes time to move through your stomach and into your intestinal tract, so eating too close to a session is basically a fast track to nausea. On the flip side, training on empty can leave you lightheaded and queasy too.

Research from 2014 has highlighted how important nutrition timing is for reducing gastrointestinal symptoms during exercise. Because blood flow to your digestive system drops during a workout (your muscles are calling), getting your meal timing right becomes essential.

Aim to eat a proper meal at least 90 minutes before you exercise. Studies show your stomach takes around two hours to empty, so giving yourself that buffer matters. If you're having a small pre-workout snack, keep it light and carb-based. Protein and fat-heavy foods take longer to digest than carbohydrates, so save those for later. Think a banana, a slice of toast, some crackers or a bit of granola.

Dairy is worth watching too, as it can cause sensitivity for some people. Keeping a short food journal, even just for a couple of weeks, can help you spot patterns and nail down what works really well (or really badly) for your body.

Wondering about workout timing in general? Find out the best time to work out here.

Watch how you're hydrating

Hydration is one of those things that sounds simple until you realise both too much and too little can make you feel terrible mid-session.

Chugging a large volume of water right before or during a workout is a common culprit for nausea, so try taking small, regular sips during your rest periods instead of gulping it down all at once. The same goes for after your session. Even if you're thirsty and sweaty, sip slowly to avoid that sloshy, nauseous feeling.

On the other end, dehydration is a very real trigger for dizziness and nausea during exercise. Make sure you're drinking enough water throughout the day, not just in the hour before you work out. Your hydration going into a session matters just as much as what you drink during it.

Don't skip your warm-up (or your cool-down)

Life is busy, and yes, sometimes the warm-up is the first thing to get sacrificed when you're short on time. But if nausea is an issue for you, this is actually one of the easiest things to fix.

Even three to five minutes of gradual movement before you start gives your body time to redirect blood flow from your digestive organs to your muscles, and lets your gut adjust to what's coming. Launching straight into a high-intensity workout from a standing start can be genuinely jarring for your system.

The same applies at the other end. Stopping abruptly after a hard session without cooling down can cause a blood pressure drop that makes nausea worse. A few minutes of gentle movement to bring your heart rate down makes a real difference, and your warm-up primes your muscles for performance too. It's not just about nausea.

Exercising in the heat

Working out in hot conditions adds a whole extra layer of stress to your body. Heat exhaustion and heat stroke are real risks during strenuous exercise, and both can leave you sweaty, lightheaded, dehydrated and nauseous, often all at once.

When temperatures are high, try to shift your workouts to earlier in the morning or later in the evening to avoid the worst of the heat. If you're training outdoors, find shade where you can. An air-conditioned indoor space is a solid backup. Moisture-wicking fabrics help your body regulate temperature more efficiently, and staying hydrated is even more important when you're sweating more than usual.

Could you be pushing too hard?

There's a real difference between a workout that challenges you and one that leaves you sprinting for the bathroom. As much as we love seeing you hit your goals, nausea is a sign your body is telling you something.

Research shows gastrointestinal symptoms during exercise are most common in people doing strenuous, sustained effort. Reducing intensity or duration, even temporarily, can make a significant difference.

Another study found nausea scores were higher during high-intensity exercise than lower-intensity activity, and especially high when training at intensity shortly after eating. So meal timing and effort level are a bit of a double act here.

If you're ramping up the intensity of your training, do it gradually. Your body needs time to adapt, and going from zero to full throttle is a reliable way to feel really gross, really quickly.

Certain exercises are more likely to trigger nausea

It's not just about how hard you're working; it's also about what you're doing. Some training styles put more mechanical pressure on your abdominal organs than others, which can make nausea more likely regardless of intensity.

Exercises to watch include heavy lifting, core-heavy movements, plyometrics, and anything that involves a lot of heavy breathing or a hunched posture. Each of these can physically compress or jostle your digestive organs in a way that your body isn't always that happy about.

If a particular exercise reliably makes you feel sick, it's worth swapping it out for a variation that achieves a similar training effect without the side effects. There's always an alternative, and there's an easy to use exercise substitutions feature in the Sweat app any time you want to switch something out.

Check your activewear fit

This one's easy to overlook, but worth checking: if your waistband is digging into your stomach, your sports bra is too tight around your ribs, or your top is restricting your movement, that physical compression can absolutely contribute to nausea and stomach discomfort during a workout.

Getting the fit right doesn't have to mean spending a fortune. It just means paying attention to where you're feeling restricted. Whether you prefer a great sports bra, baggy layers or a more fitted look, comfort is the actual goal here.

Post-workout nausea is genuinely common, but that doesn't mean you should just put up with it. If it's happening regularly, something in your routine is worth adjusting, whether that's what you eat beforehand, how hard you're pushing, how you're hydrating, or all three.

Start with the simplest changes first. Most people find that meal timing, hydration and intensity are the biggest levers. Feeling sick after a tough session every now and then isn't anything to stress about, but if you've tried the adjustments and regular post-workout nausea is still an issue, that's when it's worth getting a proper check-in with your healthcare provider to rule out anything else going on.

Working out should leave you feeling good. Full stop.