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Frequent urination at night (or nocturia)

What is frequent urination at night or nocturia?

Nocturia is the medical term for frequent urination at night. Nocturia is a symptom and not a diagnosis.

Nocturia is defined as the number of urinations (or voids) that occur during a night’s sleep with each urination both preceded and followed by sleep.

Nocturia is a very common symptom with more than 70% of people aged 70 or older affected. Men and women are affected in similar numbers in the older population.

Nocturia also happens in younger people with some studies showing that up to 30% of people aged 20 to 40 years old need to pass urine once or more at night.

How does frequent urination at night or nocturia affect quality of life?

People generally find nocturia most bothersome when it occurs more than twice per night. The severity of the effects of nocturia on quality of life relates directly to the number of times a person has to wake to pass urine at night.

Nocturia can have a significant impact on a person’s quality of life by:

  • Disturbing sleep
  • Affecting the quality of sleep
  • The effects of reduced sleep such as daytime tiredness, effects on memory and work performance
  • Increasing the risk in elderly patients of falls and injuries
  • Affecting the sleep partner of the person suffering from nocturia whose sleep can also be disturbed

How common is frequent urination at night or nocturia?

The prevalence of nocturia increases with age. Studies show that over the age of 70 years, up to 70% of people can experience nocturia. Community studies have also shown that around 30% of people wake at least once to pass urine at night.

What are the causes of frequent urination at night or nocturia?

The causes of nocturia are very complex and it is vital to determine the cause as this will greatly influence the treatment.

Potential causes include:

  • Producing too much urine in a 24-hour period - generally more than 2 litres a day. This is known as polyuria or global polyuria.
  • Producing too large a volume of urine while sleeping with normal urine production during the day - known as nocturnal polyuria.
  • Producing more urine at night than the bladder is able to hold - known as low bladder storage.
  • A combination of nocturnal polyuria and low night-time bladder storage capacity - known as mixed nocturia.
  • Poor sleep - Some people who sleep poorly then go often to urinate at night rather than being woken by the need to pass urine.

How is nocturia classified?

Nocturia is classified into 3 types that may overlap:

  • Global (i.e. both day and night) polyuria
    • Defined as production of urine volume more than 40 ml/kg per 24 hours
  • Nocturnal polyuria
    • When too much of the urine output is made overnight relative to how much is produced during the daytime
    • Defined as normal 24 hour urine volume production with more than 33% of total urine produced overnight in older adults
    • Defined as more than 20% of total urine produced overnight in younger adults
  • Bladder storage disorders
    • When a normal amount of urine is made overnight but the bladder cannot hold much urine and therefore a person voids more often overnight
    • Due to conditions which affect bladder function or cause low night time bladder capacity

The bladder diary is crucial in helping define the type and cause of nocturia. The bladder diary determines:

  • Total 24 hour urine output
  • Nocturnal urine volume
    • Proportion of total urine output that occurs at night
  • Bladder storage capacity

Assessment of frequent urination at night

The assessment of nocturia includes those factors on history and physical examination discussed in the general assessment of urinary incontinence.

History taking in patients with nocturia includes a specific assessment of:

  • Fluid intake
    • Total fluid intake
    • Intake of fluids in the hours before going to bed
    • Intake of fluids that can act as bladder irritants and increase nocturnal urine output such as alcohol and caffeine
  • Conditions that can affect nocturnal urine output such as
    • Kidney failure
    • Heart failure/ fluid retention
    • Diabetes and level of diabetic control
    • Obstructive sleep apnoea
  • Presence of other irritative bladder symptoms
  • Sleeping habits
  • Medications which affect urine volume excretion such as:
    • Diuretics (fluid tablets) and their timing
    • Lithium

Investigations in patients with nocturia include:

  • The bladder diary
  • Urine testing with a mid-stream urine specimen (MSU)
  • Blood tests to check
    • Kidney function
    • Blood sugar levels
    • Diabetic control in diabetic patients
  • An assessment of bladder emptying with a bladder ultrasound (post void residual volume assessment to check the volume of urine left behind after passing urine) that can be combined with a flow rate (to check the speed with which urine is emptied from the bladder).
  • Some patients will require further assessment with cystoscopy and urodynamic study depending on the level of symptoms and presence of suspected bladder storage disorders.

Global Polyuria (increased total urine production)

What is global polyuria?

Global polyuria is defined as a total urine volume produced per 24 hours of more than 40 ml/ kg (i.e. more than 2800 ml in 24 hours in a 70kg person).

Causes of global polyuria

The most common cause of global polyuria is excessive fluid intake. Nowadays this is related to people inadvertently “overdoing” the recommendation to increase fluid intake that is often broadcast in the media. Excessive fluid intake can also be a response to the presence of a chronically dry mouth that is a common side-effect of many medications (e.g. antidepressants).

Other causes of global polyuria include:

  • Diabetes mellitus – with poor sugar control that increases urine production and increases thirst
  • Diabetes insipidus – a rare condition in which sugar control is normal but there is a deficiency of the hormone that regulates urine production called ADH (anti-diuretic hormone).
  • Disturbances of other blood elements such as high calcium levels

Treatment of global polyuria

Global polyuria due to excessive fluid intake can be managed with fluid restriction. There is no health benefit in drinking excessive volumes of fluid beyond the body’s requirements. Metabolic conditions such as poorly controlled diabetes mellitus or diabetes insipidus benefit from further treatment by an Endocrinologist.

Nocturnal Polyuria (increased urine production at night)

What is nocturnal polyuria (increased urine production at night)?

Nocturnal polyuria or increased urine production at night is defined as an increased night-time urine output when the total 24-hour urine output is normal. High night-time urine is defined as:

  • Greater than 20% of the daily total in young adults
  • Greater than 33% of the daily total in older adults
  • Between 20-33% of the daily total in middle age

Nocturnal polyuria is present in up to 80% of people with nocturia and can only be diagnosed with the assistance of the bladder diary.

Causes of nocturnal polyuria

Causes of nocturnal polyuria include:

  • Conditions that cause fluid retention such as
    • Heart failure
    • Kidney disease
    • Liver disease
  • Excessive night time fluid intake especially of
    • Alcohol
    • Caffeine containing drinks such as coffee, tea, cola drinks
  • Obstructive sleep apnoea - a sleep disorder in which breathing is interrupted or stopped many times during sleep.
    • Referral to a Respiratory Physician or Sleep Physician for assessment with a sleep study is indicated in suspected cases of sleep disorders.
  • Reduction in night time ADH (anti-diuretic hormone) production due to
    • Ageing
    • Central nervous system problems affecting hormone production in the hypothalamus and pituitary

Treatment of nocturnal polyuria (increased urine production at night)

General measures that reduce excessive urine production at night include:

  • Reduction in fluid intake in the 4-6 hours before going to bed.
    • This includes eating foods with a high fluid content such as fruit, vegetables, salads, soup earlier in the day.
  • Avoiding caffeine (coffee and tea) as well as alcohol intake in the 4-6 hours before going to bed.
    • Caffeine and alcohol act as bladder irritants and diuretics that increase urine output overnight.
  • If ankle swelling (due to fluid retention in the tissues) is present, keeping the feet elevated as often as possible during the day and wearing compression stockings. These measures help prevent fluid accumulation.
    • Swelling or puffiness in the ankles is usually maximal in the evening and least in the morning. Overnight the fluid in the tissues that causes the swelling is reabsorbed into the bloodstream and converted into urine. This is a common cause of nocturia and nocturnal polyuria.
  • Increasing exercise levels such as walking to help reduce fluid retention in tissues.
  • Diagnosis and treatment of underlying medical conditions such as heart failure, chronic kidney disease and obstructive sleep apnoea.

Other treatments for excessive urine production at night include:

  • Use of a diuretic (“fluid” tablet) in the 6 hours before going to bed.
    • This causes increased urine production in the hours after the diuretic medication is taken. The aim is to expel the excess fluid in the afternoon and early evening rather than overnight.
  • Use of ADH (anti-diuretic hormone) medication in the evening.
    • This medication reduces urine production by increasing fluid absorption by the kidneys.
    • It must be used with caution and close monitoring in older patients as it can potentially cause excessive fluid retention and low sodium (salt) levels in the bloodstream.
    • The use of ADH is not recommended in patients with heart failure or kidney failure (impairment).

Bladder storage disorders (frequent small volume urination)

What are bladder storage disorders?

In bladder storage disorders the ability of the bladder to store urine is reduced causing nocturia (rather than due to large volumes of urine being produced at night as occurs in global polyuria and nocturnal polyuria). The night-time volumes of urine passed are often small as well as frequent in bladder storage disorders.

Bladder storage can be affected by conditions that reduce bladder capacity, cause an overactive bladder or that cause bladder irritation.

Incomplete bladder emptying due to an underactive bladder or bladder outlet obstruction (e.g. due to prostatic enlargement in men) is another potential cause of more frequent night-time urination.

What are causes of bladder storage disorders?

Potential causes of low bladder capacity at night that can result in nocturia include:

Treatment of bladder storage disorders

Treatment of nocturia due to bladder storage disorders is directed at the underlying bladder pathology, for example: