The short answer
- An oral rehydration solution is the fastest optionA sachet from a pharmacist, mixed with water, replaces salt and water together and is what the NHS points people towards when someone is older or otherwise more at risk of dehydration.
- Salt and sugar help the gut absorb water fasterPlain water is not pulled into the body as quickly, which matters most when a lot of fluid has been lost quickly.
- Skip fruit juice, fizzy and sports drinks if it's a stomach bugNHS guidance says fruit juice and fizzy drinks can make diarrhoea worse, and sports drinks have too much sugar for the salt they provide.
- Know when home fluids are not enoughCertain signs mean same-day GP advice, and others mean 999, rather than another drink and waiting to see.
Once your relative is drinking normally again, the target to stay ahead of it is at least 1,600ml (about 3 pints) a day for women and 2,000ml (about 3½ pints) for men, according to the British Dietetic Association.
What to reach for first
Oral rehydration fluids, in small sips, offered often
If your relative is dehydrated or heading that way, from a stomach bug, a hot day, or simply not drinking enough, the fastest way back is not a bigger glass of water. It is the right fluid, in small amounts, offered often. Here is a rough order of what to reach for.
An oral rehydration solution
Best first choiceA sachet from a pharmacist, mixed with water. It replaces salt and water together in a measured ratio, and the NHS points people who are older, or otherwise more at risk of dehydration, towards a pharmacist for one.
Water, in small sips, offered often
Reliable, and often enough on its ownFor everyday dehydration this is usually enough, especially alongside a bit of food. If your relative feels sick, small sips work better than a large glass, which is more likely to come straight back up.
Milk, a diluted squash or a decaf tea
Fine to mix inAll count towards fluid intake in NHS guidance, and can be easier to manage than a large glass of water when a big drink feels like too much.
Coconut water
Use with cautionIt supplies potassium but not the sodium balance of a proper rehydration solution, and is not part of NHS or pharmacist advice for treating dehydration. Anyone on a medicine that affects potassium, common in later life, should check with a pharmacist first.
Fruit juice, fizzy drinks or sports drinks
Avoid if it's a stomach bugNHS guidance for diarrhoea and vomiting is to avoid fruit juice and fizzy drinks, since they can make diarrhoea worse. Sports drinks are made for exercise, not illness, and have too much sugar for the salt they provide.
A pharmacist can recommend an oral rehydration solution and explain how to make it up: most are a sachet stirred into 200ml of water, taken after every episode of sickness or a loose stool, or through the day if the cause is simply not drinking enough. If your relative cannot manage a drink at all, water-rich food such as soup, melon or a homemade ice lolly made from a diluted squash can help in between. What are the symptoms of dehydration in the elderly? is worth checking first if you are not certain dehydration is what you are dealing with, and this sits inside the wider picture of elderly care.
Why it works faster
Why salt and sugar help the gut pull in water faster than plain water alone
This is not folk wisdom. It is how the gut absorbs fluid, and it is the reason a rehydration solution outpaces water on its own once someone is properly dehydrated.
Sodium + glucose
An oral rehydration solution pairs salt with a small amount of sugar in a measured ratio. The two are absorbed together through the gut wall, and water follows them into the bloodstream faster than it would on its own.
Guy's and St Thomas' NHS Foundation Trust, oral rehydration salts
Plain water still helps, and for everyday dehydration it is usually enough alongside a bit of food. It works more slowly because there is no salt to draw it through the gut wall in the same way, which matters most when your relative has lost a lot of fluid quickly, through a stomach bug, a fever or a hot day. Milk, a diluted squash or a decaf tea all count too, and are gentler on the stomach than a large glass of anything. Does tea count as water intake? covers tea and coffee, including the old worry about caffeine, which does not hold up at ordinary drinking levels.
What slows it down
What to leave out if the cause is a stomach bug or the heat
Some of what looks like an obvious choice for fluids either slows rehydration down or works against it, so it helps to know what to reach past as well as what to reach for.
What helps
- An oral rehydration solution from a pharmacist if sickness or diarrhoea is the cause
- Small sips, offered often, rather than a full glass at once if your relative feels sick
- Water, milk, diluted squash or a decaf tea for everyday dehydration
- Extra fluids and a closer eye on an older relative during a spell of hot weather
What to leave out
- Fruit juice or fizzy drinks if diarrhoea or vomiting is the cause, which NHS guidance says can make diarrhoea worse
- Sports drinks as a stand-in for a rehydration solution: made for exercise, with too much sugar for the salt they provide
- Coconut water in place of a rehydration solution, since it does not have the same sodium balance
- A large glass forced down quickly if your relative feels sick, which is more likely to come straight back up
Hot weather raises the risk on its own, and older people are less efficient at recognising and responding to it. The Met Office's advice for keeping older people safe in hot weather is to check in on a relative, friend or neighbour who lives alone during a warm spell, and to keep fluids going even if they do not ask for a drink. How can I get my elderly relative to drink more fluids? has more ways to build this into an ordinary day rather than a single push.
When to get more help
When home fluids are not enough
Most dehydration is put right at home within a day. Sometimes it needs more than a drink, and it helps to know what that looks like before you are in the middle of it.
- 1
Offer small sips of the right fluid
NowStart with an oral rehydration solution if you have one, or water, milk or a diluted squash if not. Little and often works better than a large glass, especially if your relative feels sick. - 2
Call NHS 111 or ask for an urgent GP appointment
Same dayIf your relative is dizzy on standing and it does not settle, breathing faster than normal, or passing noticeably less urine, this is the point to get same-day advice rather than waiting to see. - 3
Call 999 or go to A&E
EmergencyPale, grey, blue or blotchy skin, skin that feels cold, difficulty breathing, sudden confusion, or being unusually sleepy and hard to wake all mean this stage. Severe dehydration is sometimes treated with fluids given directly into a vein, which only happens in hospital and works faster than anything that can be done at home.
How serious is dehydration in the elderly? has the full list of signs by stage, and what to do if an elderly person is dehydrated covers the wider picture once you know which one applies. A carer who visits regularly is useful too, not instead of medical help but alongside it, because the same person notices sooner when a drink has gone untouched. Companion carers on PrimeCarers charge £15 to £20 an hour with our fee included, and how much does a companion carer cost? has the detail.
Questions
Questions families ask about hydrating an elderly relative quickly
An oral rehydration solution, a sachet from a pharmacist mixed with water, taken in small sips often. It replaces salt and water together, which the gut absorbs faster than plain water on its own. If you do not have one, water, milk or a diluted squash offered often is the next best option. How serious is dehydration in the elderly? has the signs to watch for as you go.
Not as a first choice. Sports drinks are made for exercise, not illness, and carry too much sugar for the salt they provide. Coconut water is high in potassium but does not have the sodium balance of a proper rehydration solution, and anyone on a medicine that affects potassium should check with a pharmacist first. A pharmacist-recommended oral rehydration solution is the better choice.
Mainly if the cause is a stomach bug. NHS guidance for diarrhoea and vomiting is to avoid fruit juice and fizzy drinks, because they can make diarrhoea worse. For everyday hydration in hot weather, or simply not drinking enough, fruit juice is fine as one of several drinks through the day.
Enough to reach the daily minimum and then keep going: at least 1,600ml (about 3 pints) a day for women and 2,000ml (about 3½ pints) for men, according to the British Dietetic Association, from ordinary drinks and food together. If your relative is unwell, a pharmacist or GP can advise on how much rehydration solution to take on top of that.
When it reaches the point of pale, grey, blue or blotchy skin, cold skin, difficulty breathing, sudden confusion, or being unusually sleepy and hard to wake. Severe dehydration is sometimes treated with fluids given directly into a vein, which is faster than anything that can be done at home and only happens in hospital. How serious is dehydration in the elderly? sets out the full list of signs by stage.
Yes. A carer who visits at the same times each day notices sooner when a drink has gone untouched, and can offer fluids as part of an ordinary visit rather than a special effort. Companion carers on PrimeCarers charge £15 to £20 an hour with our fee included. How much does a companion carer cost? has the detail.