Try a glass of water once, then look further

You are tired or foggy, maybe with a headache, and someone has told you to drink some water. For some people that is a quick, free fix. For others it is grating, because they drink plenty and are still tired. Both are describing something real, and the page below is for working out which one you are in.

Drink one glass of water slowly and see whether you feel any different; if you are tired every day, or the glass changes nothing and your urine is already pale, look beyond water and see a doctor; if you are ill, dizzy or confused, use the safety box instead.

Many people say a glass of water is the first thing to try when you feel flat, foggy or headachy, before reaching for a coffee. Some people say it lifts them almost straight away. Some people push back that “just drink water” brushes off real suffering when you are already well hydrated, and that tiredness has many causes besides thirst. What decides it, they say, is whether the tiredness comes from being short of fluid or from something else. A glass costs nothing and tells you part of that. The rest of the page is the part the glass cannot tell you.

Is water a fair first try for you?

The NHS lists tiredness among the signs of dehydration, next to thirst, a dry mouth, headache, light-headedness, dizziness, dark urine and passing less urine. So it is a fair first try if that sounds like you and there is a reason for it: a hot day or hot work, sweating, a stomach bug, a long stretch without a drink. Some people say that swapping a lot of coffee for water was what lifted their tiredness and faintness. If dizziness when you stand up does not go away, it is on the NHS’s list of reasons to call 111 or get an urgent doctor’s appointment, so do not treat it as a water problem.

Your urine is the cheap check. The NHS says to aim for a clear pale yellow, and dark urine is a sign to drink. One person corrects the idea that any yellow means you are dehydrated: pale yellow is the target, and it does not have to be clear. If your urine is already pale and you have been drinking normally, you are probably drinking enough, and running short of water is unlikely to be what is wrong with you.

How to try it

Drink one glass, slowly, over a few minutes. The NHS says to start with small sips if you feel sick. Gulping a large amount quickly is the part to avoid: some people warn that it can bring on nausea and vomiting, and say that sipping is the safer way. One person, answering advice to finish a litre in ten minutes, says the body can only take in so much at a time and that the rest is wasted or comes back up, and that it is better to drink slowly over an hour. One person says a pint is a bit much and suggests a little less, over a few minutes, for less bloating and less water passing straight through.

Then judge the glass by the bigger question and not by the next ten minutes. If you have been drinking enough all along, and the colour of your urine says so, thirst was never the problem, and the glass was never going to fix it. How long relief takes when thirst was the problem is not covered here.

One thing to know before you credit the water. One person says the lift may come from getting up and walking to the bathroom as much as from the fluid, and says it is unlikely that an ordinary day leaves you short enough to cause tiredness.

The afternoon dip

Some people say mid-afternoon tiredness is a normal dip in the day and not a sign of thirst; one person ties it to the body clock, to eating a meal and to hours of looking at a screen. Others say it is thirst and that water fixes it. What decides it, they say, is whether you have actually been under-drinking or are just meeting the usual dip. One person says a short nap beats both water and coffee for the dip. One person says the tiredness that comes from hours of steady attention at a computer is its own kind, and is easy to mistake for general tiredness.

When water is not the answer

If you drink enough and are tired every day, more water will not fix it. The NHS says that if you cannot explain why you are tired, and it has gone on for a while and is not getting better, it may be a sign of a medical condition. It says to see a GP (in the US, a primary care doctor) if you have been tired for a few weeks and are not sure why, if the tiredness gets in the way of your daily life, or if it comes with other things such as weight loss, changes in mood, or noises in your breathing when you sleep.

Some people say the cause of long tiredness can be something water cannot touch: iron storage problems, a salt imbalance, endometriosis, an underactive thyroid. The NHS lists tiredness among the common signs of an underactive thyroid and says a blood test checks the thyroid hormones, and it lists low energy, heart palpitations and breathlessness among the signs of iron-deficiency anaemia. One person says to ask about iron, magnesium, B12 and vitamin D when you are being checked for tiredness. There is a page here on asking for the right blood tests by name.

Some people say sleep apnoea can be the cause and that a sleep study is how to check for it, and one person says it can be there even when blood tests are normal. The NHS lists breathing that stops and starts, gasping or snorting noises, daytime tiredness and morning headaches, and says someone else who has seen the symptoms can come with you to the GP. It also says sleep apnoea is not only an overweight person’s condition: it also lists getting older as a risk factor, and says children and young adults can also get it. Some people say the same, that being fit does not rule it out.

The NHS also lists poor sleep, stress, depression, some illnesses and some medicines as causes of tiredness, and recommends a healthy diet, regular exercise and a steady sleep routine. One person says regular exercise raised their energy after being tired all the time.

Some people say that searching your symptoms online ends at the worst possible reading, so a check-up is better than a search. One person warns that a family doctor may not know how to investigate tiredness step by step. If a first visit finds nothing, that is a reason to go back and ask what was checked and what could be checked next, and not a reason to stop.

More water is not better

Some people say that if you are healthy and have water within reach, drinking when you are thirsty is enough and a rigid schedule is not needed. The NHS’s 6 to 8 cups is a guide, not a target to force down.

Some people warn that drinking a lot of plain water, for instance until your urine is completely clear, can wash out salts and make the tiredness worse. This page could not check a health authority on how much water is too much, so it gives no figure. What it can say, from a US National Library of Medicine page, is that low blood sodium, whatever the cause, can bring headache, tiredness, muscle cramps, confusion and convulsions, and that you should call your provider right away if you have symptoms. If you have been drinking a lot and feel a headache, nausea or confusion, stop drinking and get medical advice the same day; confusion or a seizure is an emergency (999 in the UK, 911 in the US) rather than drinking more.

After vomiting, diarrhoea or a lot of sweating, one person who explains the biology says plain water is not the best fluid, because salt and sugar help the gut take in water. The NHS says a pharmacist can recommend oral rehydration sachets that replace the lost salts and sugars. Severe dehydration is a medical matter: see the safety box above.

Who this page is not for

If you are tired every day and have been for weeks, skip the glass of water and see a doctor; the test above is for the tiredness that came on with a reason. If you are also very thirsty, peeing more often than usual (particularly at night) and losing weight, see a GP (in the US, a primary care doctor) and do not just drink more: the NHS lists that group of signs as a possible sign of diabetes.

If you have been told to limit fluids, for kidney or heart trouble for example, your doctor’s limit comes before anything here.

If you are ill and cannot keep fluids down, or the person who is tired is a baby, a child under 5 or an older adult, get medical advice rather than trying a glass of water first. This page was written for an adult who is tired and otherwise well.