Frequent Urination at Night (Nocturia): Causes, Assessment and What Helps

Three reasons people wake to urinate

Nocturia is a symptom, not a diagnosis, and it has three mechanisms that often overlap.

The bladder holds less

• Prostate enlargement in men — the growing gland reduces effective bladder capacity and irritates the bladder muscle. See enlarged prostate.
• Overactive bladder — the muscle contracts at low volumes, producing urgency day and night.
• Urinary tract infection or bladder inflammation.
• Bladder stones or tumours — uncommon, usually with blood in the urine.
• Incomplete emptying, so the bladder starts each night already partly full.

The body makes too much urine at night

Called nocturnal polyuria — producing more than about a third of the day's urine at night. Causes:

• Age — the overnight surge of antidiuretic hormone that concentrates urine fades in later life
• Fluid, alcohol or caffeine in the evening
• Sleep apnea — repeated airway collapse raises pressure in the chest, which triggers the heart to release a hormone that makes the kidneys excrete salt and water; treating apnea often halves nocturia
• Heart failure and ankle swelling — fluid that pooled in the legs by day returns to the circulation when lying flat and is excreted
• High blood sugar — glucose spilling into urine drags water with it; nocturia is a classic early sign of diabetes (see high blood sugar symptoms)
• Diuretics taken in the afternoon or evening; some blood pressure and diabetes medications (SGLT2 inhibitors); lithium
• Kidney disease, which impairs concentrating ability
• High calcium, and rarely, diabetes insipidus

Sleep is too light

Insomnia, pain, restless legs, depression and sleep apnea all fragment sleep. A person who wakes for another reason notices a modest bladder urge and attributes the waking to it. Nocturia and poor sleep feed each other.

How it is assessed

The single most useful tool is a frequency–volume chart (bladder diary): for three days, record the time and volume of every void, and fluids drunk. It shows whether the problem is small voids (bladder capacity), large night-time volumes (nocturnal polyuria) or both, and it directs treatment far better than any examination.

Beyond that: a urine test, blood tests for glucose, kidney function and calcium, prostate assessment in men (see weak urine stream and the PSA test), a check for ankle swelling and heart failure, medication review, and screening questions for sleep apnea.

What helps

For evening fluid and diet: restrict fluids in the two to three hours before bed, cut evening caffeine and alcohol, and reduce salt, which drives thirst and night-time excretion.

For fluid redistribution: elevate the legs for an hour or two in the afternoon or wear compression stockings, so fluid returns to the circulation before bedtime rather than after; take diuretics in the morning or early afternoon.

For sleep apnea: CPAP or other treatment — one of the most effective interventions for nocturia in people who have apnea.

For the bladder: alpha-blockers and other prostate treatments in men; bladder training and, if needed, antimuscarinics or mirabegron for overactive bladder; treatment of infection.

For nocturnal polyuria specifically: low-dose desmopressin (a synthetic antidiuretic hormone) reduces night-time urine production and is licensed for nocturia in some countries, with careful monitoring of blood sodium, particularly in older adults.

For sleep: treating insomnia, pain and restless legs directly.

When to see a doctor

Make an appointment if you wake twice or more most nights, if nocturia is new or worsening, or if it is accompanied by daytime urinary symptoms, thirst, weight loss, breathlessness lying flat, ankle swelling, snoring with daytime sleepiness, or blood in the urine. In older adults, nocturia is a fall risk in its own right and deserves assessment for that reason alone.

Frequently asked questions

References