Drinking water does help with diarrhea, but not in the way you might expect. Water won’t stop the diarrhea itself, but it replaces the fluid your body is rapidly losing through loose stools. That replacement is critical: dehydration is the main danger of diarrhea, not the diarrhea itself. However, plain water alone isn’t ideal, and drinking too much of it without replacing lost salts can actually create a new problem.
Why Diarrhea Drains Your Body So Fast
Your intestines normally absorb the vast majority of the fluid that passes through them. A healthy adult’s stool contains only about 200 grams of water per day. During diarrhea, that absorption process breaks down. Infections damage the cells lining the intestinal wall, making them unable to pull water back into the body. Food intolerances work differently but have the same result: undigested sugars like lactose draw water into the intestinal space through osmosis, producing watery stool.
Either way, each loose bowel movement can flush out a significant volume of water along with sodium, potassium, and other electrolytes your body needs to function. Multiple episodes per day can push you toward dehydration within hours, especially in children, older adults, and anyone who isn’t actively replacing what’s being lost.
The Problem With Drinking Only Plain Water
Plain water replaces volume but not the salts and minerals leaving your body with every loose stool. If you drink large amounts of water without any electrolyte intake, you risk diluting the sodium in your blood, a condition called hyponatremia. A case published in the Canadian Medical Association Journal illustrates this clearly: a 72-year-old woman developed dangerously low sodium levels after trying to replace diarrheal losses by drinking 2 to 3 liters of plain water per day during a bout of viral gastroenteritis. Her body was retaining the water but couldn’t hold onto enough sodium to keep pace.
This doesn’t mean water is bad. It means water works best when paired with something that contains electrolytes. For mild diarrhea in an otherwise healthy person, alternating water with salty broth or an electrolyte drink is usually enough. For prolonged or severe episodes, an oral rehydration solution (a precise mix of salts, sugar, and water) is more effective because the glucose in the solution actually helps your intestines absorb sodium and water together.
What to Drink and What to Avoid
Your best options during diarrhea include:
- Oral rehydration solutions: Available at most pharmacies, these contain the right balance of sugar and salts to maximize fluid absorption.
- Broth: Naturally contains sodium and is easy on the stomach.
- Electrolyte drinks: Sports drinks work in a pinch, though they contain more sugar than medical rehydration solutions.
- Coconut water: Research suggests young coconut water can serve as a home rehydration option for mild diarrhea, though its electrolyte balance isn’t perfect.
- Diluted fruit juice and weak tea: Gentle options that provide some variety.
What you should avoid: full-strength soda, undiluted fruit juice, and other high-sugar beverages. The fructose in these drinks acts as an osmotic agent in your gut, pulling even more water into the intestinal space and making diarrhea worse. Cola, in particular, has been shown to cause osmotic diarrhea and worsen potassium losses. Coffee and alcohol are also poor choices because both can stimulate the gut and increase fluid loss.
How Much Fluid You Actually Need
There’s no single number that works for everyone, but a practical rule is to drink a cup (about 240 ml) of fluid after each loose bowel movement, on top of your normal daily intake. Sip steadily rather than gulping large amounts at once, which can trigger nausea and make things worse. If you’re vomiting alongside the diarrhea, ice chips and very small, frequent sips are easier to keep down than full glasses.
For children, the same principle applies on a smaller scale. Infants and toddlers dehydrate faster than adults, so keeping up with losses matters even more. Watch for dry lips and tongue, and in infants, fewer than six wet diapers a day is a warning sign. In toddlers, no urination for eight hours signals the child is falling behind on fluids.
Signs You’re Getting Dehydrated
Mild dehydration shows up as thirst, darker urine, a dry mouth, and a dry cough. You might feel lightheaded when standing up. As dehydration worsens, you may stop sweating, produce very little urine, or feel confused. These more severe signs mean your body has lost enough fluid that it’s struggling to maintain basic functions, and oral fluids alone may not be enough to catch up.
What to Eat While Recovering
You may have heard of the BRAT diet (bananas, rice, applesauce, toast), but following it strictly is no longer recommended. The American Academy of Pediatrics advises against it for children because it’s too low in nutrients and may actually slow recovery if followed for more than 24 hours. For adults, those foods are fine for the first day or two at your sickest, but they lack protein, calcium, vitamin B12, and fiber.
A better approach is to eat as tolerated, starting with bland, easy-to-digest foods. If you’re actively vomiting, stick to liquids until that settles. Once you can keep things down, try brothy soups, oatmeal, boiled potatoes, saltine crackers, or dry cereal. As your stomach stabilizes, work in more nutritious options like scrambled eggs, skinless chicken, and cooked vegetables. Smaller, more frequent meals tend to sit better than large ones.
The core takeaway: water helps, but it’s not the whole answer. Pair it with electrolytes, eat when you can, and pay attention to how your body responds. Most bouts of diarrhea resolve within a few days, and staying ahead of fluid losses is the single most important thing you can do during that window.