Polyuria refers to the production of abnormally large amounts (more than 2.5 litres per day for adults) of urine. Normal urine production in an adult is 1 to 2 litres. Urine volume is influenced by factors such as fluid intake, blood pressure, dietary habits, temperature, medications, mental state and general health. As people age, their kidneys become less effective and urinary symptoms become more common. Polyuria is a fairly common symptom which is often noticed when it occurs at night. Polyuria is often accompanied by excessive fluid intake (polydipsia).
Polyuria is a commonly experienced symptom.
It can be caused by any of the following:
- Too much fluid intake, particularly fluids containing caffeine or alcohol.
- Too much salt or glucose (if diabetic).
- Drug use, especially diuretics.
- Diabetes (both diabetes insipidus and diabetes mellitus).
- Psychogenic polydipsia, most common in women over age 30.
- Renal failure.
- Radiographic tests that use a contrast media (urine volume will increase for up to 24 hours following the dose). If the excessive urination occurs over several days, and it is not explained by medications or increase in fluids, you should see your doctor.
The doctor will perform a thorough history and physical examination. They may want to do some tests to investigate the cause of the polyuria, which may include:
- Urinalysis (analysis of the urine): for diabetes (looking for glucose, ketones) and signs of renal disease.
- Urine culture (testing for infections).
- Blood glucose levels.
- Blood electrolyte balance (test for renal function).
- 24 hour urine volume.
- Fluid deprivation test (the intake of fluids is restricted to see if the urine volume decreases). Further specialist investigations may be needed, such as renal ultrasound or biopsy, if the cause is not clear.
Polydipsia refers to excessive fluid intake. It is often associated with polyuria. When investigating polydipsia, patients are usually asked to keep a record of drinks taken for the day, with a view to reducing fluids if this is proven to be the cause of the excess amount of urine production. Thirst is an important symptom which is useful in deciding if the cause of the polydipsia is due to a medical condition or for social reasons.
Polydipsia may be due to:
- Diabetes mellitus
- Diabetes insipidus
- Raised calcium levels in the blood (Hypercalcaemia)
- Phosphorus poisoning
- Compulsive water drinking (habit)