If your baby is showing signs of dehydration, the most important step is to increase fluids right away, typically through more frequent breastfeeding, formula feeding, or an oral rehydration solution designed for infants. Mild dehydration is common during illness and usually responds well to extra fluids at home. But if your baby seems unusually sleepy, has no tears when crying, or has deeply sunken eyes, that points to moderate or severe dehydration, which needs medical attention fast.
How to Spot Dehydration in a Baby
Babies can’t tell you they’re thirsty, so you have to read physical cues. The earliest and most reliable sign is a drop in wet diapers. A healthy baby older than about four days typically produces at least six wet diapers in 24 hours. Fewer than that, especially during an illness with vomiting or diarrhea, is the first signal that fluid intake isn’t keeping up with losses.
Other signs of mild dehydration include a dry or sticky mouth and tongue, fewer tears than usual when crying, and a slightly sunken soft spot (fontanelle) on top of the head. Your baby may seem fussier than normal or more eager to drink when offered fluids. At this stage, dehydration is very manageable at home.
As dehydration gets worse, the signs become more obvious. Moderate dehydration looks like noticeably sunken eyes, a dry tongue, very few or no tears, and your baby acting restless or unusually tired. You can also check capillary refill: gently press on your baby’s thumbnail or big toenail for about three seconds until the pink color fades, then release. The pink should return in under two seconds. If it takes two to three seconds, that suggests moderate dehydration. Longer than three seconds points to something more serious.
When Dehydration Is an Emergency
Severe dehydration is a medical emergency. A baby with severe fluid loss will look very sick. The signs include extreme drowsiness or limpness, deeply sunken eyes and fontanelle, completely absent tears, a parched mouth, and cold or mottled hands and feet. If you pinch the skin on the back of your baby’s hand and it takes more than two seconds to flatten back out, that’s another red flag.
A rapid heart rate is one of the body’s earlier responses to significant fluid loss. By the time blood pressure actually drops, organ perfusion is already compromised. If your baby is limp, unresponsive, breathing rapidly, or has cool and blotchy skin, go to the emergency room immediately. Don’t try to rehydrate at home at this point.
Rehydrating a Mildly Dehydrated Baby
For babies who are breastfeeding, the best first step is simply to nurse more often. Offer the breast every one to two hours, even if feedings are shorter than usual. Breast milk provides the right balance of fluids, sugars, and electrolytes, and a sick baby’s stomach may tolerate frequent small feeds better than large ones.
For formula-fed babies, continue offering formula at full strength. Don’t water it down unless specifically told to by a healthcare provider, because diluted formula throws off the electrolyte balance your baby needs. Offer smaller, more frequent bottles if your baby is vomiting.
If your baby has been vomiting or has diarrhea and isn’t keeping breast milk or formula down well, a pediatric oral rehydration solution (sold over the counter at most pharmacies) is the go-to option. These solutions are specifically formulated with the right concentration of salts and sugars to help a small body absorb fluid efficiently. For mild to moderate dehydration, the general guideline is 50 to 100 milliliters per kilogram of body weight over three to four hours. For a 7-kilogram baby (about 15 pounds), that works out to roughly 350 to 700 ml over that window, given in small, frequent sips or spoonfuls.
If your baby keeps vomiting, try offering just a teaspoon or two every few minutes rather than a full bottle. Many babies who refuse a bottle will accept small amounts from a syringe or spoon. Patience matters here. Slow and steady intake often stays down better than a large volume at once.
Fluids to Avoid
Plain water is not safe for rehydrating babies under six months and is a poor choice even for older infants during illness. A baby’s kidneys aren’t mature enough to handle large volumes of plain water, and it contains no electrolytes. In documented cases, infants given large amounts of water developed dangerously low sodium levels, leading to seizures. This condition, water intoxication, is entirely preventable by sticking to breast milk, formula, or oral rehydration solutions.
Juice, soda, and sports drinks are also off the table. Their high sugar content can actually pull more water into the intestines and make diarrhea worse, a process called osmotic diarrhea. Sports drinks are designed for adult athletes, not infants. They contain sugar levels that can worsen fluid loss and electrolyte concentrations that don’t match what a baby needs.
What Causes Dehydration in Babies
The most common trigger is a stomach virus that causes vomiting, diarrhea, or both. Babies lose fluid faster than older children and adults because they have a higher surface-area-to-body-weight ratio and their kidneys are less efficient at conserving water. A few hours of vomiting can tip a small baby into dehydration surprisingly quickly.
Fever also increases fluid loss through the skin, even when you can’t see obvious sweating. Babies who are too congested to nurse well, or who refuse bottles because of a sore throat, can become dehydrated simply from not taking in enough. Hot weather without adequate fluid intake is another common cause, particularly in younger infants who depend entirely on milk for hydration.
Tracking Recovery at Home
Once you’ve started increasing fluids, the clearest sign that rehydration is working is an increase in wet diapers. You’re looking for a return to at least six wet diapers in 24 hours, with urine that’s pale yellow rather than dark or concentrated. Other encouraging signs include a moist mouth, tears returning when your baby cries, and improved alertness or energy.
If your baby isn’t producing any wet diapers over a six-to-eight-hour stretch, won’t take fluids, or seems to be getting worse despite your efforts, that’s the point to call your pediatrician or head to urgent care. Moderate dehydration that doesn’t improve with oral fluids sometimes requires IV rehydration in a clinical setting, which works quickly and is very routine in pediatric care.
Keep in mind that the underlying illness, usually a virus, may take a few days to resolve. Your goal during that window is simply to keep fluid intake ahead of losses. Smaller, more frequent feeds are almost always better tolerated than large ones, and persistence with a spoon or syringe can make a real difference when a baby is reluctant to drink.