Merck Manual

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Some Causes and Features of Excessive Urination

Some Causes and Features of Excessive Urination


Common Features*


Disorders that cause primarily frequent urination

Cystitis Bladder Infection Bladder Infection (bladder infection)

Usually in women and girls

A frequent and urgent need to urinate

Burning or pain during urination

Sometimes fever and pain in the lower back or side

Sometimes blood in the urine or foul-smelling urine


Typically during the last several months of pregnancy

A doctor's examination

Sometimes urinalysis (to look for a urinary tract infection Urinary Tract Infections (UTIs) )

Mainly in men over 50

Slowly worsening urinary symptoms, such as difficulty starting urination, a weak urine stream, dribbling at the end of urination, and a sensation of incomplete urination

Often detected during a digital rectal examination

Blood tests to measure the PSA level

Sometimes ultrasonography

Prostatitis Prostatitis (prostate infection)

A tender prostate detected during a digital rectal examination

Often fever, difficulty starting urination, and burning or pain during urination

Sometimes blood in the urine

In some cases, symptoms of a long-standing blockage in the urinary tract (including a weak urine stream, difficulty passing urine, or dribbling at the end of urination)

Urinalysis and urine culture and a digital rectal examination

Radiation cystitis (bladder damage caused by radiation therapy)

In people who have had radiation therapy of the lower abdomen, prostate, or perineum (the area between the genitals and anus) for treatment of cancer

A doctor's examination

Sometimes insertion of a flexible viewing tube into the bladder ( cystoscopy Cystoscopy ) and biopsy

Weakness and numbness in the legs

Sometimes an obvious injury

MRI of the spine

Occasional episodes of squeezing pain in the lower back, side (flank), or groin that comes and goes

Depending on where the stone is, possibly frequent urination or sudden, severe urges to urinate


Ultrasonography or CT of the kidneys, ureters, and bladder

Substances that increase the excretion of urine, such as caffeine, alcohol, or diuretics

In otherwise healthy people shortly after they drink beverages containing caffeine or alcohol or in people who recently started taking a diuretic

Only a doctor's examination

Unintentional passage of urine, most often when bending, coughing, sneezing, or lifting (called stress incontinence)

After water is inserted into the bladder, measurement of changes in pressure and the amount of urine in the bladder (cystometry)

Disorders that primarily increase the volume of urine

Excessive thirst

Often in young children

Sometimes in obese adults, who may already be known to have type 2 diabetes

Measurement of blood sugar (glucose) level

Excessive thirst that may appear suddenly or develop gradually

Sometimes in people who have had a brain injury or brain surgery

Blood and urine tests, done before and after people are deprived of water, then given antidiuretic hormone (water deprivation test)

Sometimes blood tests to measure the antidiuretic hormone level

Excessive thirst that develops gradually

Onset in the first few years of life or in children whose family members drink excess amounts of water

Blood and urine tests

Sometimes a water deprivation test

Diuretic use

In otherwise healthy people who recently started taking a diuretic

Sometimes in people who take a diuretic surreptitiously (for example, competitive athletes or other people trying to lose weight)

Usually only a doctor's examination

Drinking too much fluid (polydipsia) often due to a mental health disorder

Sometimes in people known to have a mental health disorder

Similar to tests for central diabetes insipidus

Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

CT = computed tomography; MRI = magnetic resonance imaging; PSA = prostate-specific antigen.