If you need to rehydrate fast, healthdirect's advice for mild dehydration is to take small, frequent sips of water or an oral rehydration solution and move somewhere cool. Sipping steadily works better than gulping a litre at once, and an oral rehydration solution replaces the salts you lose through vomiting or diarrhoea as well as the water.
I build a water tracker, so I spend a lot of time reading what health bodies actually say about drinking. Below is that advice in one place, with links to the sources.
At a glance: how to rehydrate fast
| Situation | What to drink | How |
|---|---|---|
| Mild dehydration (hot day, missed drinks) | Water | Small, frequent sips somewhere cool |
| Vomiting or diarrhoea | Oral rehydration solution | Sip clear fluids every 5 to 10 minutes |
| Long, sweaty exercise | Water, plus food or a sports drink | Drink steadily during and after |
| Hangover | Water | Sip steadily; only time clears the alcohol |
What's the fastest way to rehydrate?
- Sip, don't chug. Small, frequent sips are easier on your stomach and are healthdirect's first piece of advice for mild dehydration.
- Get somewhere cool and rest, so you stop losing more fluid as sweat.
- Use an oral rehydration solution (ORS) if you're losing fluid through vomiting or diarrhoea. healthdirect says these work better than plain water because they contain the right concentration of salts to replace both fluids and electrolytes.
In Australia you can buy oral rehydration solutions at pharmacies and supermarkets, as powders, tablets or ready-made drinks. healthdirect also gives a home recipe if you can't get to a shop: 1 litre of water, 6 level teaspoons of sugar and half a teaspoon of salt. Measure carefully, because the balance matters.
How long does it take to rehydrate?
There's no single number, because it depends on how much fluid you've lost. Cleveland Clinic says the signs of mild dehydration can start to improve in as little as five to ten minutes of drinking. Feeling fully back to normal usually takes longer, so keep sipping until the signs in the rehydration checklist below have cleared.
Children follow a slower, measured plan. For a child over 10 kg with mild dehydration, the Royal Children's Hospital Melbourne suggests up to about 100 ml (half a cup) an hour for four hours, then reassessing. If a child isn't improving, see a doctor.
Water, oral rehydration solution or sports drink?
| Drink | When it helps | Watch out for |
|---|---|---|
| Water | Most mild dehydration, everyday top-ups | Drinking a lot very quickly (see overhydration) |
| Oral rehydration solution | Vomiting, diarrhoea, gastro | Mix powders exactly as the pack says |
| Sports drink | Long or very sweaty exercise, hours in the sun | healthdirect advises avoiding them when you're dehydrated from illness |
| Soft drink or juice | Not recommended for rehydrating | Sugary drinks can make diarrhoea worse |
| Milk | Hydrates well (see the FAQ below) | Not a substitute for ORS during gastro |
| Alcohol | Never | Works against you while you rehydrate |
Sports drinks are where the advice gets confusing. For an hour or less of moderate exercise, Cleveland Clinic says water is enough; for longer sessions or hours in the heat, a sports drink may help replace electrolytes. But healthdirect lists soft drinks and sports drinks among the drinks to avoid when you're dehydrated, particularly with gastro, where an oral rehydration solution is the better choice. Our guide to drinking for exercise and heat goes further, and does coffee count as water? covers everyday drinks.
How do you rehydrate after vomiting or a hangover?
After vomiting or diarrhoea: sip clear fluids every 5 to 10 minutes, as healthdirect suggests, rather than drinking a lot at once. An oral rehydration solution is the best choice because it replaces salts as well as water.
After a big night: there's no quick cure for a hangover. healthdirect says time is the only way to remove alcohol from your body, though drinking water helps with the dehydration side of it. Better Health Channel notes hangovers generally last up to 24 hours. Sip water through the morning, eat when you can, and skip the "hair of the dog".
How do you know you're rehydrated?
- Your urine is pale yellow or straw-coloured. healthdirect says that usually means you're well hydrated. Cleveland Clinic adds that completely clear, colourless urine can mean you're drinking more than you need.
- You're weeing normally again, not just once or twice a day.
- Thirst, a dry mouth, headache and dizziness have gone.
When is dehydration an emergency?
healthdirect says severe dehydration needs urgent medical attention. Signs include:
- fast breathing or a fast heart rate;
- confusion;
- cold hands and feet;
- sunken eyes;
- passing little or no urine, or feeling faint when you stand up.
In an emergency in Australia, call 000. If you're not sure, you can call healthdirect on 1800 022 222 (NURSE-ON-CALL in Victoria) any time. Babies and young children dehydrate quickly; Better Health Channel advises taking a child you think is dehydrated straight to a hospital emergency department.
How do you stop it happening again?
Most dehydration happens slowly: a hot day, a long meeting, a forgotten water bottle. The fix is boring but it works. Drink steadily through the day instead of catching up at night, and drink more when it's hot or you're active. Our 12 habits for drinking more water make that easier, and the free water intake calculator gives you a daily number to aim for.
That's the problem I built Hydration Hero to solve. It sets a personal daily goal, reminds you at intervals you choose, and its weather and activity Power Ups update your goal on hot or active days. It's on iPhone and Apple Watch and Android.
Frequently asked questions
Is milk better than water for rehydrating?
In a 2016 study of 72 healthy men who were not dehydrated, skim and full-fat milk and an oral rehydration solution were held in the body longer than still water over four hours. It wasn't tested on people who were already dehydrated, so for vomiting or diarrhoea an oral rehydration solution is still the better choice.
Can you rehydrate too fast?
Yes. Drinking a large amount of plain water in a short time can dilute the sodium in your blood, a rare but dangerous condition called hyponatraemia. Cleveland Clinic says more than about a litre an hour is probably too much. Sip steadily instead.
Do electrolyte tablets work?
Some tablets and powders sold in Australian pharmacies are oral rehydration solutions, which are designed for vomiting and diarrhoea. Others are sports electrolyte products. Cleveland Clinic notes most people get all the electrolytes they need from food. If you are unsure which to buy, ask a pharmacist.
How much water should I drink after being dehydrated?
There is no fixed amount. Keep sipping until your urine is pale yellow and you are weeing normally, and avoid drinking more than about a litre an hour. For a daily target, Australian guidelines suggest about 2.6 litres of fluids a day for men and 2.1 litres for women, more in the heat.
Does coconut water rehydrate you?
Coconut water contains potassium, sodium and magnesium, but Cleveland Clinic says it may not be any better than water. It isn't made to the salt and sugar balance of an oral rehydration solution, so use a proper solution if you have vomiting or diarrhoea.
Read next
- Signs of dehydrationThe early symptoms, and when it's serious
- OverhydrationHow much water is too much
- Water for exercise and heatHow much extra you need when you sweat
- Does coffee count as water?Which drinks help and which work against you
Sources
- Dehydration, healthdirect
- Vomiting, healthdirect
- Gastroenteritis, healthdirect
- Drinking water and your health, healthdirect
- How alcohol affects your health, healthdirect
- How alcohol affects your body, Better Health Channel
- Water: a vital nutrient, Better Health Channel
- Dehydration fact sheet, Royal Children's Hospital Melbourne
- Dehydration, Cleveland Clinic
- A randomized trial to assess the potential of different beverages to affect hydration status (Maughan et al., 2016), American Journal of Clinical Nutrition
- The health benefits of coconut water, Cleveland Clinic
Last updated 14 November 2026. This is general information, not medical advice. If you have a heart, kidney or liver condition, or have been told to limit fluids, follow your doctor's advice. In an emergency in Australia, call 000.