What to drink when you're sick: fever, vomiting, diarrhea

2026-10-30

When you're sick, keep drinking, little and often. With a fever or a cold, water, diluted squash, herbal tea and broth are all fine. With vomiting or diarrhea you lose salts as well as water, so an oral rehydration solution (ORS) from the pharmacy is the best choice once you're losing a lot. Avoid fruit juice and fizzy drinks, which can make diarrhea worse. Get medical help if you can't keep fluids down, or if you see signs of serious dehydration.

Why illness dries you out

Being ill raises the amount of fluid you lose and often lowers how much you take in:

Fever raises your body temperature, and you lose more water through sweating and breathing. The NHS advice on fever in adults is to drink plenty of fluids, water being best, and to drink enough that your pee is light yellow and clear.
Vomiting and diarrhea remove water and electrolytes (sodium, potassium) quickly. That is why they cause most illness-related dehydration, and why they need more than plain water.
Feeling unwell blunts appetite and thirst. Food normally supplies part of your daily water, so a day without meals is also a day with less fluid.

Fever, colds and flu

For a fever or a respiratory infection, there's no special drink. Aim for steady, normal intake rather than forcing liters down:

Water, diluted squash, herbal or weak tea, warm water with lemon and honey, and clear soups all count.
Warm drinks can soothe a sore throat; cold drinks or ice lollies can help when you're hot.
Pace yourself: a glass at each waking hour is easier than trying to catch up at night.

How much extra is "enough"? Nobody has a precise figure. A Cochrane review looked for trials testing whether extra fluids help people with acute respiratory infections and found none, so "drink lots of fluids" is sensible advice rather than a proven treatment. The practical goal is simply to avoid dehydration: pale urine, no strong thirst, no dizziness when you stand up.

Vomiting: small sips, not big gulps

If you're vomiting, a large drink often comes straight back up. Small amounts stay down far better:

Give your stomach a short rest after vomiting, then start with a sip or two.
Take a small sip every few minutes. CDC guidance for children with gastroenteritis suggests about 5 ml (a teaspoon) every 5 minutes, increasing gradually; adults can follow the same idea with slightly larger sips.
If that stays down for an hour or so, increase the amount.
If you vomit again, pause and start over with smaller sips.

Ice chips or frozen ORS lollies are another way to get fluid in slowly.

Diarrhea: when to use oral rehydration salts

Mild diarrhea in a healthy adult usually needs nothing more than extra water and normal food when you feel able. The NHS recommends drinking plenty, such as water or squash, with small sips if you feel sick.

When you're losing a lot of fluid, though, you need to replace sugar and salts too. That's what oral rehydration solutions are for. The WHO describes ORS as a mixture of clean water, salt and sugar; the small amount of glucose helps your gut absorb sodium and water together. You buy them as sachets of powder at the pharmacy and mix them with the stated amount of water.

ORS is worth using if:

you have frequent watery diarrhea or repeated vomiting
you notice signs of dehydration (dark urine, peeing less, dizziness)
you're older, have a long-term condition, or are caring for a young child

Follow the packet's mixing instructions exactly. A pharmacist can tell you which product suits you or your child.

What about sports drinks, juice and soda?

Sports drinks: the CDC says drinks without caffeine or alcohol can help with mild dehydration but may not replace important nutrients and minerals. They contain less sodium and more sugar than ORS. Fine for mild cases; ORS is better for heavy losses. More in sports drinks vs water.
Fruit juice and fizzy drinks: the NHS advises avoiding them, because they can make diarrhea worse. Children especially shouldn't have them while ill.
Caffeine and alcohol: best avoided until you're better. Alcohol in particular makes it harder to stay hydrated.
Milk: fine for most people once vomiting has stopped, unless it upsets your stomach.

What about food?

Eat when you feel able. Plain foods like toast, rice, soups and bananas are easy to tolerate, and the NHS suggests avoiding fatty or spicy food at first. Soups and broths are useful because they provide fluid and some salt at the same time. For babies and young children, carry on with breast milk or formula; the WHO stresses continued feeding during diarrhea.

Signs that you're getting dehydrated

Watch for:

dark yellow, strong-smelling urine, or peeing less often
thirst, dry mouth and lips
headache, tiredness
dizziness or light-headedness, especially when standing up

A fuller list, including what to look for in children and older adults, is in signs of dehydration in adults.

When to get medical help

Most stomach bugs and fevers pass on their own. The NHS says vomiting usually stops within 1 or 2 days and diarrhea within 5 to 7 days. Get medical advice (your doctor, or NHS 111 in the UK) if:

you keep vomiting and can't keep fluids down
you still have signs of dehydration after using rehydration sachets
you have bloody diarrhea or bleeding from the bottom
diarrhea lasts more than 7 days or vomiting more than 2 days
a high temperature isn't getting better with home treatment, or is getting worse

Seek emergency care if someone has confusion, is unusually sleepy or hard to wake, has difficulty breathing, has cold or blotchy skin, or vomits blood or something that looks like coffee grounds. These can be signs of serious illness or shock. Babies, young children, older adults, pregnant women and people with kidney disease, heart disease, diabetes or a weakened immune system get dehydrated faster: contact a doctor sooner, and ask before changing fluid intake if you've been told to restrict fluids.

A simple plan for a sick day

Keep a drink within reach at all times, ideally something you like.
Sip a little every 10 to 15 minutes rather than drinking large amounts at once.
Switch to ORS if diarrhea or vomiting is frequent.
Check your urine color a few times a day; aim for pale yellow.
Keep track of roughly how much you've had, especially if you're caring for someone else and need to tell a doctor.

That last point is easier than it sounds. In Water Tracker, you can log each small amount with a tap from a widget or your Apple Watch without getting out of bed, then see the day's total at a glance.

Bottom line

When you're ill, drink steadily and in small sips. Water is fine for fevers and colds; use oral rehydration salts when vomiting or diarrhea are heavy, and skip juice, soda and alcohol. Watch your urine color, and don't wait to get help if you can't keep fluids down or show signs of serious dehydration.

This article is general information, not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor how much you should drink.