General
Excessive thirst
A persistent, abnormal thirst that is not satisfied by drinking — which can simply follow heat, exercise or salty food, but when constant, especially with passing lots of urine and weight loss, is an important warning sign of diabetes.
Education and reference only. This explains the common causes of excessive thirst and the warning signs that need urgent help, in plain language — it is not a diagnosis or a substitute for advice from a clinician. If you feel very unwell or are worried, seek medical help.
Quick answer
What is excessive thirst?
Feeling thirsty is a normal response to losing fluid through heat, exercise, salty or spicy food, or alcohol, and it usually settles once you drink. Thirst becomes a symptom worth investigating when it is persistent and excessive — a dry, unquenchable thirst that drives you to drink large amounts and is not relieved by doing so, particularly when it comes with passing large volumes of urine, especially needing to get up at night to pass water.
- Get urgent help: Call 999 if excessive thirst comes with drowsiness, confusion, deep or heavy breathing, tummy pain and vomiting — especially in a child — as this can mean diabetic ketoacidosis, a life-threatening emergency. Seek a same-day appointment for new, persistent thirst with passing lots of urine, unexplained weight loss and extreme tiredness, which can mean newly developed diabetes.
- Self-care: When thirst follows hot weather, exercise, alcohol or salty food, the remedy is simply to rehydrate with water and to moderate salt, caffeine and alcohol, which all increase fluid loss.
About excessive thirst
Feeling thirsty is a normal response to losing fluid through heat, exercise, salty or spicy food, or alcohol, and it usually settles once you drink. Thirst becomes a symptom worth investigating when it is persistent and excessive — a dry, unquenchable thirst that drives you to drink large amounts and is not relieved by doing so, particularly when it comes with passing large volumes of urine, especially needing to get up at night to pass water. This combination is one of the classic warning signs of diabetes, in which a high level of sugar in the blood draws water out through the kidneys, causing both heavy urination and the thirst that follows. Unexplained weight loss, tiredness and blurred vision can accompany it. Less commonly, persistent thirst reflects dehydration, certain medicines, or other hormonal problems. Because new, persistent thirst with frequent urination can be the first sign of diabetes, it should be checked rather than ignored.
When to get help
Call 999 or go to A&E if excessive thirst comes with any of these warning signs:
- Call 999 if excessive thirst comes with drowsiness, confusion, deep or heavy breathing, tummy pain and vomiting — especially in a child — as this can mean diabetic ketoacidosis, a life-threatening emergency.
- Seek a same-day appointment for new, persistent thirst with passing lots of urine, unexplained weight loss and extreme tiredness, which can mean newly developed diabetes.
- Seek urgent help if thirst is accompanied by signs of severe dehydration such as a very dry mouth, dizziness, sunken eyes and passing little urine.
- Get checked promptly if a child is suddenly drinking and wetting far more than usual, or becoming tired and losing weight.
When to see a doctor
Thirst that settles after you rehydrate and that has an obvious cause such as heat or exercise needs no medical attention. You should arrange to be seen, however, if you have a persistent, excessive thirst that is not relieved by drinking, particularly if you are also passing large amounts of urine, getting up at night to pass water, losing weight without trying, or feeling very tired or noticing blurred vision — these can be the first signs of diabetes and warrant a same-day or prompt appointment and a blood or urine test. Treat thirst with drowsiness, confusion, heavy breathing and vomiting, especially in a child, as a 999 emergency.
Not sure how urgent it is? It is always OK to call NHS 111 for advice, day or night.
What can cause it
Common causes of excessive thirst
Excessive thirst has many possible causes. Each links to a full, plain-language guide to that condition — what it is, how it's treated and when to seek help.
What helps
Self-care and what you can do
When thirst follows hot weather, exercise, alcohol or salty food, the remedy is simply to rehydrate with water and to moderate salt, caffeine and alcohol, which all increase fluid loss. Sipping water steadily through the day, rather than gulping large amounts at once, keeps you comfortably hydrated. The important caution is that persistent, excessive thirst is not a problem to manage by drinking ever more — if your thirst is constant, you are passing a lot of urine, getting up repeatedly at night, losing weight without trying, or feeling unusually tired, these are signs to be tested rather than self-treated. While you arrange a check, keep drinking water normally to avoid dehydration, but do seek medical advice promptly.
Answers
Excessive thirst: frequently asked questions
Why am I always thirsty even though I drink lots?
A persistent thirst that is not relieved by drinking, especially with passing large amounts of urine, can be a sign of diabetes, in which a high blood sugar level draws water out through the kidneys. This warrants a prompt check.
Is excessive thirst a sign of diabetes?
It can be. Constant thirst together with frequent urination, unexplained weight loss, tiredness and sometimes blurred vision are classic early warning signs of diabetes and should be tested rather than ignored.
When is thirst an emergency?
Thirst with drowsiness, confusion, deep or heavy breathing, tummy pain and vomiting — particularly in a child — can mean diabetic ketoacidosis, which is life-threatening. Call 999 in this situation.
Can dehydration alone cause excessive thirst?
Yes. Heat, exercise, salty or spicy food and alcohol all increase fluid loss and cause thirst that settles once you rehydrate. Thirst that is constant and not relieved by drinking, though, needs to be checked.
Sources
Where this is drawn from
- NICE CKS: Diabetes - type 2.
- Diabetes UK: signs and symptoms.
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