How effective is oral rehydration therapy for dehydration?

An oral rehydration solution combines water with glucose and salts in proportions that help the small intestine absorb fluid. This makes it more useful for dehydration caused by diarrhoea or vomiting than plain water alone, because those illnesses also remove electrolytes.

It works only if enough solution is absorbed and the underlying fluid loss is being managed. Marked dehydration, ongoing heavy losses, reduced alertness, shock, or an inability to drink may need assessment and fluids through a vein. Read more about [Dehydration](/conditions/dehydration/) and the treatment itself at [Oral Rehydration Therapy](/treatments/acute-and-urgent-care/oral-rehydration-therapy/).

Choose a prepared oral rehydration solution. Follow the mixing instructions exactly, because adding too much or too little water changes its salt concentration. Take small, regular sips; after vomiting, restart slowly. Continue breastfeeding, and return to light food as tolerated.

Monitor practical signs such as improving thirst, a less dry mouth, more normal urine, and better alertness. Do not use sports drinks or very sweet drinks as a substitute when diarrhoea or vomiting is significant.

Get urgent medical help for fainting, confusion, severe weakness, very little urine, inability to keep fluids down, blood in vomit or stool, fast breathing, or worsening symptoms. Infants, older adults, pregnant people and those with kidney or heart problems should seek advice early.

Ask what caused the dehydration, which solution is appropriate, how much and how often to drink, which signs show recovery, and whether medicines or intravenous fluids are needed.