Polyuria is a condition where the body urinates more than usual and passes excessive or abnormally large amounts of urine each time you urinate.
Polyuria is defined as the frequent passage of large volumes of urine – more than 3 litres a day compared to the normal daily urine output in adults of about 1 to 2 litres.
It is one of the main symptoms of diabetes (both type 1 and type 2 diabetes) and can lead to severe dehydration, which if left untreated can affect kidney function.
Causes of polyuria
Polyuria is usually the result of drinking excessive amounts of fluids (polydipsia), particularly water and fluids that contain caffeine or alcohol.
It is also one of the major signs of diabetes mellitus. When the kidneys filter blood to make urine, they reabsorb all of the sugar, returning it to the bloodstream.
In diabetes, the level of sugar in the blood is abnormally high. Not all of the sugar can be reabsorbed and some of this excess glucose from the blood ends up in the urine where it draws more water.
This results in unusually large volumes of urine.
Other causes of polyuria include:
Diabetes inspidus – a condition unrelated to diabetes mellitus that affects the kidneys and the hormones that interact with them, resulting in large quantities of urine being produced
Kidney disease
Liver failure
Medications that include diuretics (substances that increase the excretion of water from the body/urine)
Chronic diarrhoea
Cushing’s syndrome
Psychogenic polydipsia – excessive water drinking most often seen in anxious, middle-aged women and in patients with psychiatric illnesses
Hypercalcemia – elevated levels of calcium in the blood
Pregnancy
Polyuria as a symptom of diabetes
As well as being one of the symptoms of undiagnosed diabetes, polyuria can also occur in people with diagnosed diabetes if blood glucose levels have risen too high.
If blood glucose levels become too high, the body will try to remedy the situation by removing glucose from the blood through the kidneys. When this happens, the kidneys will also filter out more water and you will need to urinate more than usual as a result.
