Dehydration in babies can happen quickly, especially during diarrhoea, vomiting, fever, poor feeding, or hot weather, and it is important to recognise the signs early. Common signs of dehydration in babies include dry mouth or lips, crying with very few or no tears, sunken eyes, reduced urine or fewer wet diapers than usual, unusual sleepiness, irritability, weakness, and poor feeding. In young babies, the soft spot on the head may also appear slightly sunken. Mild dehydration can often be improved by continuing breastfeeding or formula feeding frequently and giving small amounts of ORS (oral rehydration solution) if advised by a doctor. Fluids should be given slowly and regularly, especially after loose motions or vomiting. Avoid giving sugary soft drinks or packaged juices because they may worsen diarrhoea. It is very important to seek medical help immediately if the baby is unable to drink, keeps vomiting everything, has a very high fever, fast breathing, no urine for several hours, severe sleepiness, cold hands or feet, blood in stool, seizures, or appears very weak and difficult to wake up, because severe dehydration can become dangerous quickly in babies. Even if symptoms seem mild, babies can worsen faster than adults, so early medical advice is always safer if you are worried. With quick attention, proper fluids, and treatment of the underlying cause, most babies recover well.