MedDroidSymptom guide
Excessive thirst: causes, warning signs & what to do
Written & medically reviewed by Dr. Sanjay Anbu, MBBS · Last reviewed
Medically reviewedFeeling thirsty after heat, exercise or salty food is normal. Constant thirst that does not go away despite drinking — especially with passing a lot of urine — is a classic sign of high blood sugar.
Possible causes
Common causes of excessive thirst
- High blood sugar from diabetes — thirst plus frequent urination and tiredness
- Dehydration from heat, sweating, diarrhoea or vomiting
- Dry mouth from medicines, mouth-breathing or Sjögren’s syndrome
- High calcium levels, or kidney problems
- Medicines such as water tablets (diuretics)
- Rare hormone problems that affect how the kidneys hold water (diabetes insipidus)
Self-care
What you can do now
- Drink water regularly; avoid sugary drinks, which make high sugar worse
- Notice whether you are also passing much more urine, or waking at night to urinate
- In hot weather, add an oral rehydration solution if you are sweating heavily
- If you have diabetes, check your sugar reading when you feel unusually thirsty
Red flags
When to see a doctor urgently
- Thirst with vomiting, stomach pain, fast breathing or drowsiness (possible diabetic emergency) — call your local emergency number (108/112 in India)
- Confusion, fainting or very little urine with dehydration
- Extreme thirst in a child, with weight loss or bedwetting that is new
- Thirst lasting more than a few days without an obvious reason
Checks
Tests a doctor may suggest
Depending on your history and examination, a doctor may suggest some of these. Your doctor decides which, if any, you need.
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Related pages
References
Sources & further reading
Frequently asked questions
Is constant thirst a sign of diabetes?
It can be. Excessive thirst together with frequent urination, tiredness and weight loss are common signs of high blood sugar. A sugar test is quick and cheap.
Why am I always thirsty even after drinking water?
Diabetes, dehydration, a dry mouth from medicines, and less commonly high calcium or hormone problems can cause it. See a doctor if it persists.
How much water should I drink in a day?
Needs vary with weather, activity and health. Pale-yellow urine is a simple guide. People with heart or kidney disease may need a limit set by their doctor.