Most people urinate about 4 to 6 times a day, mostly in the daytime. Normally, adults pass between 3 cups (700 milliliters) and 3 quarts (3 liters) of urine a day. Excessive urination can refer to
An increased volume of urine (polyuria)
A normal volume of urine with the need to go more often (urinary frequency)
Both
Urinary frequency may be accompanied by a sensation of an urgent need to urinate (urinary urgency). Many people particularly notice polyuria because they have to get up to urinate during the night (nocturia). Nocturia also can occur if people drink too much fluid too close to bedtime, even if they drink no more than normal overall.
(See Overview of Urinary Tract Symptoms.)
Causes of Excessive or Frequent Urination
Some of the causes of increased urine volume differ from those of too-frequent urination. However, because many people who produce excessive amounts of urine also need to urinate frequently, these two symptoms are often considered together.
The most common causes of urinary frequency are
Bladder infections (the most common cause in women and children)
Noncancerous enlargement of the prostate gland (benign prostatic hyperplasia—the most common cause in men over 50)
The most common causes of polyuria in both adults and children are
Uncontrolled diabetes mellitus (most common)
Drinking too much fluid (polydipsia)
Diabetes insipidus
Diabetes insipidus causes polyuria because of problems with a hormone called antidiuretic hormone (or vasopressin). Antidiuretic hormone helps the kidneys reabsorb fluid. If too little antidiuretic hormone is produced (a condition called central diabetes insipidus) or if the kidneys are unable to properly respond to it (nephrogenic diabetes insipidus), the person urinates excessively.
People with certain kidney disorders (such as interstitial nephritis or kidney damage resulting from sickle cell anemia) may also urinate excessively because these disorders also decrease the amount of fluid reabsorbed by the kidneys.
Rarely, urinary frequency is caused by spinal cord injury or disorder.
Evaluation of Excessive or Frequent Urination
Many people are embarrassed to discuss problems related to urination with their doctor. But because some disorders that cause excessive urination are quite serious, people who urinate excessively should be evaluated by a doctor. The following information can help people know when to see a doctor and what to expect during the evaluation.
Warning signs
In people with excessive urination, certain symptoms and characteristics are cause for concern. They include
Weakness of the legs
Fever and back pain
Abrupt onset or onset during the first few years of life
Night sweats, cough, and weight loss, especially in a person who has an extensive smoking history
A mental health disorder
When to see a doctor
People who have leg weakness should go to the hospital immediately because they may have a spinal cord disorder. People who have fever and back pain should see a doctor within a day because they may have a kidney infection. People who have other warning signs should see a doctor within a day or two. People without warning signs should schedule an appointment as soon as is convenient, usually within a few days to a week, although waiting longer is usually safe if symptoms have been developing over weeks or longer and are mild.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What they find during the history and physical examination often suggests a cause of excessive urination and the tests that may need to be done (see table Some Causes and Features of Excessive Urination).
Doctors ask about
Amounts of fluid drunk and urinated to determine whether the problem is related to urinary frequency or to polyuria
How long symptoms have been present
Whether any other urination problems are present
Some obvious findings may also give clues to the cause of polyuria. For example, polyuria that starts during the first few years of life is likely caused by an inherited disorder such as central or nephrogenic diabetes insipidus or type 1 diabetes mellitus.
In women, the physical examination usually includes a pelvic examination and the taking of samples of cervical and vaginal fluid to check for sexually transmitted infections. In men, the penis is examined for presence of a discharge, and doctors do a digital rectal examination to examine the prostate.
Testing
Doctors do a urinalysis and often urine culture on most people. The need for other testing depends on what doctors find during the history and physical examination (see table Some Causes and Features of Excessive Urination). If doctors are not sure whether the person is actually producing more urine than normal, they may collect and measure the amount of urine produced over 24 hours. If people actually have polyuria, doctors measure the blood glucose level. If diabetes mellitus is not the cause of polyuria and no other cause, such as excess intravenous fluids, is clearly responsible, other testing is necessary. The levels of electrolytes and concentration of certain salts (osmolarity) are measured in the blood, urine, or both, often after the person is deprived of water for a time and after the person is given antidiuretic hormone.
Treatment of Excessive or Frequent Urination
Essentials for Older People: Excessive or Frequent Urination
Older men often urinate frequently because the prostate usually enlarges with age (a condition called benign prostatic hyperplasia). In older women, frequent urination is also more common because of many factors, such as weakening of the pelvic supporting tissues after childbirth and the loss of estrogen after menopause. Both older men and older women may be more likely to take diuretics, so these drugs may contribute to excessive urination. Older people with excessive urination often need to urinate at night (nocturia). Nocturia can contribute to sleep problems and to falls, especially if a person is rushing to the bathroom or if the area is not well lit. Treatments directed at benign prostatic hyperplasia include oral drugs and surgery for some cases.
Key Points
Urinary tract infections are the most common cause of urinary frequency in children and women.
Uncontrolled diabetes mellitus is the most common cause of polyuria.
Benign prostatic hyperplasia is a common cause in men over 50.
