It is best to give the oral rehydration solution frequently and in small volumes. Too much fluid at one time may cause vomiting. Give as much fluid as the child will take. Most children with no or only some dehydration will drink as much oral rehdration fluid as they need to replace the fluid lost. Children with some dehydration are usually very thirsty. However, children with severe dehydration are very ill and may refuse to drink. Usually 25 ml (5 teaspoons) can be given every 10 minutes. If the child vomits, try again in another 10 minutes. If the child refuses the fluid or continues to vomit the fluid, nasogastric or intravenous therapy may be needed. This is particularly important if a vomiting child appears to be dehydrated.