What to notice

How long the increased thirst has been present
Whether drinking seems to relieve the thirst
Whether you have recently been exercising more, sweating heavily or spending time in hot weather
Whether you are also urinating more often than usual
Whether you wake at night because of thirst or urination
Whether there is fatigue, unexplained weight change or another new symptom
Whether any medicines or supplements recently changed

Common cause groups

Dehydration and fluid loss

Hot weather, exercise, sweating, vomiting or diarrhoea can increase the body's need for fluids and make you feel more thirsty.

Diet and daily habits

Salty foods, changes in eating habits and some drinks can temporarily increase thirst.

Medicines and other health factors

Some medicines and illnesses can affect fluid balance or cause a dry mouth that feels like increased thirst.

Blood glucose or metabolic causes

Persistent thirst can occur when blood glucose is high, particularly when it happens together with frequent urination, although thirst alone does not mean that diabetes is present.

Associated signs

Frequent urination
Fatigue
Dry mouth
Night-time urination
Unexplained weight change
Dizziness or weakness

How it may be assessed

A doctor will usually ask how long the thirst has been present, how much you are drinking, whether you are urinating more often and whether there have been changes in medicines, activity or general health. If the thirst is persistent or unexplained, blood glucose and selected kidney-related tests may be considered.

Assessment and investigations

Blood Glucose

A blood glucose test may help assess whether current blood sugar levels could be relevant when excessive thirst occurs together with symptoms such as frequent urination.

HbA1c

HbA1c provides information about average blood glucose over a longer period and may be considered when diabetes or ongoing blood-sugar changes need assessment.

Kidney Function Test

Kidney-function testing may be considered when persistent thirst occurs with urinary changes or when broader fluid and kidney health needs assessment.

When to get checked

Consider medical assessment if excessive thirst persists despite normal drinking, keeps returning, noticeably changes how much you drink, or occurs together with frequent urination, fatigue, unexplained weight change or other new symptoms.

Urgent warning signs

Seek prompt medical care if excessive thirst occurs with severe weakness, confusion, repeated vomiting, inability to keep fluids down, or signs of significant dehydration or rapidly worsening illness.

Frequently asked questions

Why am I always thirsty?

Feeling unusually thirsty can happen because of dehydration, hot weather, exercise, diet, medicines or some health conditions. Persistent thirst, especially with other symptoms, may be worth assessing.

Can excessive thirst be a sign of diabetes?

Excessive thirst can occur with diabetes, particularly when it is accompanied by frequent urination, but thirst has many possible causes and cannot diagnose diabetes by itself.

What is polydipsia?

Polydipsia is the medical term for excessive or unusually persistent thirst and drinking. The reason for it depends on the person's symptoms, fluid needs and overall health.

Screening context

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