Dehydration
Dehydration is not an illness in itself but a state: the body has lost more water and salt than it has taken in.
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Medicines commonly prescribed for Dehydration
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: ORAL SOLUTION/SUSPENSION, -Active substance: Oral rehydration salt formulationsManufacturer: Casen Recordati S.L.Prescription not requiredDosage form: ORAL SOLUTION/SUSPENSION, 43.6 mg / 24 mg / 258 mg / 32 mg / 149 mg / 5 g / 58.5 mg / 71 mgActive substance: Oral rehydration salt formulationsManufacturer: Laboratorios Ern S.A.Prescription requiredDosage form: ORAL SOLUTION/SUSPENSION, 20 g / 1.5 g / 3.5 g / 2.9 gActive substance: Oral rehydration salt formulationsManufacturer: Casen Recordati S.L.Prescription not required
Dehydration is not an illness in itself but a state: the body has lost more water and salt than it has taken in. There is nearly always a cause behind it — a gut infection, hot weather, a high fever, poorly controlled diabetes. The treacherous part is that a person holds out for a long time on reserves and then goes downhill fast. The blood thickens, blood pressure drops, and the kidneys and the head are the first to suffer. It is hardest on those who cannot ask for a drink or simply do not feel thirst: babies and older people. What follows is how to spot a shortage of fluid before it turns dangerous, what to rehydrate with, and the point at which home measures stop working.
How to tell that fluid is running short
Urine changes before wellbeing does. If there is noticeably less of it, if it has darkened to the colour of strong tea and smells sharp, the body is short of fluid however lively the person feels. The rest follows:
- dry mouth, flaking lips, a sticky tongue, almost no saliva;
- dizziness or a swimming head, especially on standing up from a chair or a bed;
- sluggishness, difficulty gathering your thoughts, everything done more slowly than usual;
- a dull headache that lifts once the person has had a proper drink;
- eyes that look sunken and a drawn face;
- skin on the back of the hand that is slow to flatten out after being pinched into a fold.
In a baby the same thing looks different, and a parent has to go by indirect signs: the soft spot on the top of the head sinks, crying comes without tears, the nappy stays dry for several hours in a row, and the child is either unusually sleepy and limp or, the other way round, cannot be settled at all, feeds weakly at the breast or turns away from the bottle.
Thirst deserves a word of its own. It is a poor guard: it turns up once the losses are already sizeable, and in older people and in anyone taking a diuretic it may not turn up at all. So in hot weather, with diarrhoea or with a high fever, you drink by the clock rather than when you feel like it.
When it becomes a matter of hours
Call an ambulance — 112 across Europe, or your local emergency number — without waiting for the morning if an adult or a child shows any of the following:
- confusion, odd behaviour, slurred speech, the person is hard to wake or does not respond the way they normally would;
- no urine for eight hours or more, or a baby whose nappy has stayed dry through several changes in a row;
- a fast, weak pulse, fast deep breathing, skin that is cold, pale or blotchy;
- fainting, or vision going dark and not clearing even once the person is lying down;
- vomiting that has gone on for more than a day, with not even a sip of water staying down;
- bloody diarrhoea, black stools, vomit with blood in it, or green vomit in a child;
- a seizure;
- in someone with diabetes: high blood glucose, breath smelling of acetone, noisy deep breathing, abdominal pain;
- in a baby under three months, any temperature above 38 °C (100.4 °F) together with refusal to feed.
Nobody drives in this state: ask to be taken, or call an ambulance. Bring a list of your medicines — the doctor needs to see straight away the diuretics, the blood pressure drugs and the glucose-lowering ones, because with dehydration some of them have to be stopped for a while.
Why more fluid leaves than comes in
Most often the loss is obvious: vomiting and diarrhoea from a gut infection, work or training in the heat, a high fever that burns extra water for every degree. A large amount of alcohol belongs here too — it suppresses the hormone that holds water back, and half of the morning-after wreckage is plain dehydration. Diuretics and some blood pressure and diabetes drugs push more fluid out, which people do not always keep in mind.
There is a second group of causes worth knowing about, because in those dehydration is the first thing anyone notices. If thirst has become unquenchable, if urine comes in large volumes and looks pale, and the person is losing weight and strength, that is a reason to have blood glucose measured. The result comes back in mmol/L and is read together with the symptoms, not on its own. This is how diabetes announces itself, and left alone it ends in a severe state with acetone on the breath and deep laboured breathing. Less commonly, stubborn thirst and heavy urine output point to a failure of the hormone that keeps water in the kidney, to a raised blood calcium, or to adrenal insufficiency. All of this is sorted out with tests, not by drinking more.
What to rehydrate with, and how
With mild losses ordinary drinks are enough: water, weak tea, diluted juice. But when fluid is going out with vomiting and diarrhoea, sodium, potassium and sugar go with it, and water alone will not fix that — it thins the blood further. What is needed then is a ready-made oral rehydration sachet from the pharmacy, mixed so that water is absorbed in the gut together with salt and glucose. The pharmacist will point out the right version for an adult and a separate one for a child; the amounts are printed on the box.
- Drink in small sips and often, a couple of spoonfuls every few minutes. A full glass downed at once, with nausea in the picture, almost always comes straight back.
- If it has been vomited up, wait ten minutes and start again with the smallest portions.
- Keep the solution cool but not ice-cold, and mix it exactly as the instructions say: a concentrated solution does harm.
- Sugary fizzy drinks, energy drinks, undiluted juice and strong coffee are no use for rehydrating — they draw water into the bowel and make diarrhoea worse.
- Alcohol is out entirely for those days.
- Eat as soon as you feel like it: going hungry does not speed recovery up.
When the one who is dehydrated is a child
A baby carries on with the breast or with formula, offered more often than usual but for shorter spells. Formula is not watered down: diluted, it delivers too little salt and too few calories and only makes things worse. Between feeds give the rehydration solution by the spoonful, and to an older child a few sips after every loose stool. Usual food stays: cereal and vegetables can remain on the plate.
What is better not given: fruit juice and sweet fizzy drinks, which make diarrhoea worse; home-mixed salt solutions made by eye, since getting the salt concentration wrong in a child is easy and dangerous; and antidiarrhoeal medicines that no doctor has prescribed. A child needs to be seen by a doctor if diarrhoea and vomiting have not settled within a day, if they are limp, if they refuse to drink, if the nappy is dry, or if they are under six months old.
Older people: a case of their own
Past sixty-five the sense of thirst dulls and the kidneys hold water less well. Many drink little on purpose, because of incontinence or to avoid getting up so often at night. Add diuretics to that, and one hot week brings it all together. In older people dehydration shows itself atypically: not as thirst but as sudden confusion, weakness, a fall, or simply the person having "gone strange". Confusion like that is often taken for dementia when replacing the fluid would have been enough.
If you are caring for an older person, simple things help: keep the drink in sight and in a light cup, offer it with every meal and every round of tablets, turn tea into a reason to sit down together. Foods with plenty of water in them work well — soup, broth, jelly, yoghurt, watermelon, melon, cucumber. And it is worth glancing once a day at the colour of the urine: it is the quickest way to know whether enough is going in.
Keeping it from getting that far
There is one guide and it is simple: urine should be pale, the colour of straw, and the toilet should be visited several times a day. Dark urine is a signal to drink more; completely clear urine in large volumes means you can drink less. There is no universal figure in litres — the need depends on weight, on the weather, on how hard you are working, and on heart and kidney conditions, where the fluid allowance is agreed with the doctor separately.
Drink more than usual, and ahead of time, in hot weather, during sport, with fever, vomiting and diarrhoea, and also on a flight and in a dry heated room. If you are sweating hard for a long stretch, water on its own is not enough: you need drinks with salt in them, or ordinary food alongside the drink. Offer a child a drink every hour on a hot day without waiting to be asked, and take water with you on a walk and on the road.
Online consultation
Remotely you can settle the main question: whether you will manage at home or it is time to go in. The doctor works through how many days fluid has been going and by what route, judges from your description of the urine and of how you feel how deep the losses are, says what to rehydrate an adult or a child with and in what amounts, and explains which signs to watch over the next twenty-four hours. A separate and important part of the conversation is medication: which of your drugs are better paused while you are ill, so as not to load the kidneys. And if thirst has been there for weeks without diarrhoea and without heat, the doctor will say which tests to have done so that diabetes is not missed. The signs in the emergency section are not dealt with remotely — with those you call an ambulance straight away.
This material is for information only and does not replace medical advice.
Consult with a doctor about Dehydration
Discuss your symptoms and possible next steps with a doctor online.
Online doctors for Dehydration
Discuss your symptoms and possible next steps for Dehydration with a doctor online.
