Excessive urination (polyuria): causes, red flags and when to see a GP

Before looking at causes, it helps to work out which kind of problem this is. Polyuria means passing an unusually large total volume of urine over the day, often with strong thirst. Frequency, by contrast, means going many times, often with small amounts, urgency or discomfort. The NHS page on diabetes insipidus gives a reference point: most healthy adults pass urine 4 to 7 times in 24 hours, and it advises seeing a GP if you are peeing more than normal or needing to pee small amounts at frequent intervals.

Keeping a record helps the clinician. The NHS enlarged prostate page says doctors usually ask for a record, kept for at least 3 days, of how much you drink and how often and how much you pee. A simple chart of times and approximate volumes, including night-time trips, can separate a fluid-balance problem from a bladder one.

Many ordinary things increase urine production: drinking more fluid, caffeine and alcohol, and medicines that make you pee. The more medically important causes are below.

For people with diabetes, the NHS lists thirst, needing to pee more often, stomach pain, nausea or vomiting, deep breathing, fruity breath, tiredness, sleepiness, confusion and blurred vision as symptoms of diabetic ketoacidosis. It says to call 999 or go to A&E if blood ketones are over 3 mmol/L or urine ketones above 2+, or if you do not know your ketone levels but have these symptoms, or if you have these symptoms and have not been diagnosed with diabetes.

The NHS enlarged prostate page says to ask for an urgent GP appointment or call 111 if you have blood in your urine, pain when peeing, or cannot pee at all. For urinary infection it lists, among reasons for an urgent appointment, being over 65, being a man, having diabetes, pregnancy, a very high or low temperature or shivering, pain in the lower tummy or under the ribs at the back, blood in the urine, or symptoms that worsen quickly or fail to improve in 48 hours. It says to call 999 or go to A&E if someone with a suspected UTI is confused, drowsy or has difficulty speaking.

Dehydration can follow if urine output is high and fluids are not replaced. The NHS says to seek urgent advice for unusual tiredness, dizziness on standing that does not go away, or dark yellow pee or peeing less than normal, and to take extra care in babies, children and older adults.

• Thirst and heavy urination with vomiting, fruity breath or drowsiness in someone with diabetes.

• Being unable to pass urine at all.

• Blood in the urine, or pain on passing it with fever or shivering.

• Back or flank pain with a high temperature, which could be a kidney infection.

• Confusion or drowsiness together with urinary symptoms.

• Unquenchable thirst that persists for days, which the NHS says should always be investigated.

The GP typically asks how long it has been going on, how much you drink, whether you pass large or small amounts, whether you get up at night, whether there is pain, urgency or leaking, and about thirst, weight loss, tiredness, medicines (including diuretics and lithium) and family history of diabetes. The NHS type 2 diabetes page lists risk factors: being white and over 40, or over 25 from South Asian, Chinese, Black African or Black Caribbean backgrounds, a close relative with diabetes, excess weight and inactivity, or a condition such as high blood pressure.

Examination may include checking blood pressure, examining the abdomen and, in men with prostate symptoms, a rectal examination to feel the size of the prostate, as the NHS describes.

A urine dipstick can detect glucose, blood, protein, ketones and signs of infection. The NHS says type 2 diabetes is diagnosed with a blood test of blood glucose, with results usually taking a few days. NICE CKS gives the diagnostic thresholds of an HbA1c above 48 mmol/mol (6.5 per cent) or a random plasma glucose above 11.1 mmol/L for persistent hyperglycaemia.

Other tests depend on the picture: kidney function and salts, a PSA blood test and urine flow test for prostate problems, bladder ultrasound or cystoscopy, and for suspected diabetes insipidus the NHS says a GP can arrange a number of tests to find the cause. A specialist may use further tests, such as a water deprivation test, to tell the types apart.

Do not cut back on fluids to reduce the trips to the toilet. The NHS prostate page warns that cutting down too much on fluids can cause problems such as urinary infections, although it suggests reducing alcohol and caffeine, and drinking less just before bed or before going out while still drinking enough during the rest of the day.

Keep a record of drinks and urine, note how often you get up at night, and bring a list of medicines. If thirst is intense and persistent, do not wait to see whether it passes.