Drinking water does not make diarrhea worse. In fact, replacing lost fluid is one of the most important things you can do when you have diarrhea, because the real danger isn’t the diarrhea itself but the dehydration it causes. What can cause problems, though, is drinking only plain water in large amounts without replacing the salts and minerals your body is also losing. The distinction matters, and understanding it will help you recover faster.
Why It Feels Like Water Makes Things Worse
When you drink a glass of water during a bout of diarrhea, you might notice another trip to the bathroom shortly after. This can create the impression that water is fueling the problem. But what’s actually happening is that your gut is already in a state where it’s pushing contents through too quickly or secreting extra fluid into the intestine. The water you drank didn’t cause that. Your intestines were going to move things along regardless.
There are two broad types of diarrhea, and they behave differently. Osmotic diarrhea happens when something in your gut (like undigested lactose or certain sweeteners) pulls water into the intestine. This type actually stops when you stop eating. Secretory diarrhea, caused by infections or toxins, continues whether you eat or drink or not. In neither case does drinking water itself trigger more diarrhea. The underlying cause is what’s driving the loose stools.
How Your Gut Absorbs Water
Your small intestine doesn’t just passively soak up water like a sponge. It relies on a transport system that moves sodium and glucose from inside the gut into your cells, and water follows along with them. A specific transporter protein called SGLT1 handles this process, shuttling glucose and water together through the same pathway. Research published in The Journal of Biological Chemistry confirmed that water molecules essentially ride along the same route as glucose through this transporter.
This is why plain water alone isn’t absorbed as efficiently as water paired with a small amount of salt and sugar. Your intestine needs those ingredients to pull water across the gut wall and into your bloodstream. When you’re healthy, your normal diet provides plenty of both. But during diarrhea, when you may not be eating much and you’re losing sodium rapidly, plain water sits in the gut longer and gets absorbed less effectively.
The Real Risk: Losing Salt, Not Gaining Water
The actual concern with drinking large volumes of plain water during diarrhea isn’t that it worsens the diarrhea. It’s that diarrhea causes you to lose sodium, and if you replace only the water without the sodium, your blood sodium levels can drop too low. This condition, called hyponatremia, is uncommon in adults drinking normal amounts, but it becomes a real possibility in specific situations.
When your body loses fluid from diarrhea, it triggers a hormone that tells your kidneys to hold onto water. At the same time, your kidneys start retaining sodium aggressively. If you then drink a lot of plain water or low-solute fluids like tea, you’re adding water back without enough sodium to match. In mild cases this causes headaches and nausea. In severe cases, particularly in young children or elderly adults, it can cause confusion or seizures. This is why health organizations emphasize rehydration solutions over plain water for significant diarrhea episodes.
What to Drink Instead of Plain Water
The gold standard for rehydration during diarrhea is an oral rehydration solution. The formula recommended by the World Health Organization contains 75 millimoles per liter each of glucose and sodium, with a total concentration slightly lower than your blood. This specific ratio takes advantage of that glucose-sodium transport system in your gut, maximizing water absorption even when the intestine is inflamed or irritated. You can buy ORS packets at most pharmacies, or make a rough version at home with six teaspoons of sugar and half a teaspoon of salt dissolved in a liter of clean water.
Coconut water is a reasonable natural alternative. It contains about 33 milliequivalents per liter of sodium and 51 milliequivalents per liter of potassium, along with a small amount of natural sugar. That’s less sodium than a proper ORS, so it’s not a perfect substitute for severe diarrhea, but it’s significantly better than plain water for mild cases. Sports drinks fall somewhere in between: they contain electrolytes and carbohydrates, but many commercial versions have too much sugar, which can actually pull more water into the gut and worsen loose stools.
Plain water is still fine to drink. You don’t need to avoid it. The goal is simply to make sure it’s not the only thing you’re consuming. Alternating between plain water and something containing electrolytes, or sipping broth, gives your body what it needs to actually retain the fluid you’re taking in.
Eating During Diarrhea
The old advice to stick to bananas, rice, applesauce, and toast (the BRAT diet) is no longer recommended as a strict regimen. While those foods are gentle on the stomach, they lack the vitamins and nutrients your body needs to recover. The American Academy of Pediatrics has specifically moved away from recommending BRAT for children, noting that following it for more than 24 hours may actually slow recovery by depriving the gut of the nutrition it needs to heal.
A better approach is to eat bland, soft foods when you feel able to, and gradually return to a normal diet as your symptoms improve. Your body needs calories and protein to repair the intestinal lining. Avoiding greasy, spicy, or very high-fiber foods for a day or two makes sense, but restricting yourself to four nutritionally limited foods does not.
Signs That Rehydration Isn’t Working
Even when you’re drinking the right fluids, it helps to know what dehydration actually looks like so you can catch it early. In adults, the clearest sign is dark urine or urinating much less frequently than normal. Dry mouth, dizziness when standing, and a lack of tears when crying are other reliable indicators.
In children and infants, watch for fewer than four wet diapers in 24 hours, no tears, dry mouth and tongue, sunken eyes, or grayish skin. Infants may also develop a sunken soft spot on the top of the head. Bloody or black stools, or vomiting that continues beyond four to six hours, are signs the situation has moved beyond what fluids alone can manage.