Excessive thirst

Category: General & Whole-Body Symptoms · All general symptoms

What it can feel like

Excessive thirst means feeling thirsty most of the time even though you are drinking plenty — waking at night to drink, or always wanting a drink at hand. It often goes together with passing more urine than usual and a dry mouth.

Possible causes

A symptom can have many causes, and most are not serious. The lists below group conditions this symptom can be associated with — common causes first. They are possibilities to discuss with a clinician, not a diagnosis.

Common causes

Thirst can be associated with hot weather, exercise, salty food, alcohol, fever and simply not drinking enough. It is also a side effect of some medicines, and of breathing through the mouth at night.

Other possible causes

Persistent excessive thirst can be associated with raised blood sugar from diabetes — the classic pairing is thirst with passing lots of urine, tiredness and weight loss. Less commonly it relates to raised calcium levels, kidney problems or rare hormone conditions affecting water balance.

Red flags — when to seek help promptly

Thirst with vomiting, stomach pain, rapid breathing or drowsiness — this can be a diabetes emergency
Thirst with passing very large amounts of urine day and night
Thirst with unexplained weight loss and blurred vision
A child with new heavy thirst, bedwetting and weight loss

What a clinician may do

A clinician will ask how much you drink and pass, examine you, and check your blood sugar — often there and then — plus blood tests for kidney function, calcium and salts, and a urine test. The pattern of these results usually points to the cause.

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Frequently asked questions

How much drinking is too much?

There is no single number, because needs vary with weather and activity. The pattern that matters is a clear change — drinking much more than your household around you, waking repeatedly at night to drink, and passing much more urine than usual.

Is thirst with frequent urination always diabetes?

Diabetes is the first thing clinicians check, because it is common and treatable, but it is not the only cause — medicines, calcium levels and kidney conditions can produce a similar pattern, which is why blood and urine tests are arranged.

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Please note: This page is educational information about a symptom. A symptom alone cannot diagnose any condition, and the causes listed here are possibilities, not a diagnosis. If you are worried about a symptom — especially one that is new, severe, getting worse or not going away — please see your own clinician, who can examine you and arrange tests. In an emergency, call your local emergency number.