Water is essential when you have diarrhea, but plain water alone isn’t enough. Each loose stool pulls water, sodium, potassium, and other electrolytes out of your body, and replacing only the water without those minerals can actually make things worse. The best approach combines water with electrolytes and small amounts of sugar, either through an oral rehydration solution or a mix of clear fluids and salty foods.
Why Plain Water Isn’t Enough
Diarrhea doesn’t just drain water from your body. It disrupts the sodium-potassium exchange system in your intestines, which is the main mechanism your gut uses to absorb fluid. When that system breaks down, you lose significant amounts of sodium, potassium, magnesium, and chloride with every trip to the bathroom. Severe or prolonged episodes can also deplete bicarbonate, pushing your blood chemistry toward dangerous territory.
Drinking only plain water replaces the fluid but dilutes the sodium that remains in your bloodstream. This creates a condition called hyponatremia, where cells begin to swell as sodium concentrations drop. Mild cases cause nausea, headache, fatigue, and muscle cramps. Severe cases, where sodium plummets rapidly, can lead to confusion, seizures, and in rare situations, coma. Children are particularly vulnerable: the Canadian Paediatric Society warns that giving a child only water during frequent diarrhea can cause dangerously low blood sugar or sodium levels.
What to Drink Instead
Oral rehydration solutions (ORS) are the gold standard. These are specific mixtures of water, salts, and glucose designed to be absorbed even when your gut is losing large volumes of fluid. The formula recommended by the World Health Organization contains 75 milliequivalents per liter each of glucose and sodium, with a total concentration low enough to pull water into your cells rather than push it out. You can buy pre-mixed ORS products at most pharmacies, or use ORS powder packets dissolved in water.
The glucose in these solutions isn’t just for energy. It activates a co-transport system in the intestinal lining that carries sodium and water along with it, essentially creating a back door for absorption when the normal route is compromised. This is why the sugar-to-salt ratio matters so much, and why homemade alternatives can be tricky to get right.
For adults with mild diarrhea, you can also stay hydrated with a combination of water, broth, and small amounts of salty crackers or pretzels. The goal is to get both fluid and electrolytes in. Aim to drink between 100 and 240 milliliters (roughly half a cup to one cup) of rehydration fluid after each loose bowel movement.
Drinks That Make Diarrhea Worse
Sugary drinks are a common mistake. Fruit juice, soda, sweetened tea, and sports drinks with high sugar content can actually pull more water into your intestines, loosening stools further. Sugar stimulates the gut to secrete water and electrolytes, which is the opposite of what you need. Fructose is one of the biggest culprits: many people who consume more than 40 to 80 grams of fructose per day will develop diarrhea even when they’re healthy. A single 16-ounce cola contains close to 30 grams of fructose, so it doesn’t take much to cross that threshold during an illness.
Broth and rice water, while often suggested as home remedies, also lack the correct balance of salts and sugar to effectively replace what you’re losing. They’re not harmful in moderation, but they shouldn’t be your primary source of rehydration.
Hydration Guidelines for Infants and Children
Babies under 12 months should not be given plain water during diarrhea. Breast milk and formula already contain the right balance of fluids and nutrients, and adding extra water can dilute an infant’s already low sodium reserves. For breastfed babies, nurse more frequently. For formula-fed babies, offer formula at the usual concentration but more often.
For older infants and toddlers with frequent watery stools, an oral rehydration solution is the safest option. Fruit juice should be avoided entirely, as the high sugar content worsens diarrhea in small children. If a child cannot keep down enough fluid or ORS to stay hydrated, that’s a situation requiring prompt medical attention.
Signs Hydration Isn’t Working
Even with the right fluids, some episodes of diarrhea outpace what your body can absorb. Watch for these signs that dehydration is setting in despite your efforts:
- Extreme thirst or dry mouth that doesn’t resolve with drinking
- Dark-colored urine or urinating much less than usual
- Dizziness, lightheadedness, or unusual fatigue
- Skin that stays pinched when you pull it up and release it, rather than snapping back flat
- Sunken eyes or cheeks
In infants, the warning signs include no wet diapers for three hours or more, no tears when crying, a sunken soft spot on the skull, and unusual drowsiness. Any of these signals mean oral rehydration has fallen behind and professional help is needed.
A Practical Rehydration Plan
For most adults with a short bout of diarrhea, a simple plan works well. Start sipping an ORS or clear broth as soon as symptoms begin, rather than waiting until you feel thirsty. Thirst is a late signal, meaning you’re already mildly dehydrated by the time you notice it. Drink a cup of rehydration fluid after each loose stool, and take small, frequent sips between episodes rather than gulping large amounts at once, which can trigger nausea.
Plain water is fine as part of your overall fluid intake, but it shouldn’t be the only thing you’re drinking. Pair it with sources of sodium and potassium: salty crackers, bananas, or an ORS. If diarrhea lasts more than two days in an adult, or if you notice any dehydration symptoms, the situation has moved beyond what home hydration can manage on its own.