Excessive Urination (Polyuria)

Excessive urination vs frequent urination

These are often confused, but they point to different causes.

Most adults pass about 0.8 to 2 liters (27 to 68 oz) of urine a day. If you are going often but passing small amounts, see frequent urination.

Common causes

Drinking a lot

The simplest explanation. Large intakes of water, sports drinks, coffee, tea, soda or beer all increase urine. Caffeine and alcohol also act as diuretics. Alcohol blocks the hormone that tells the kidneys to save water.

Diuretic medicines

"Water pills" such as furosemide and hydrochlorothiazide, used for blood pressure, heart failure and swelling, increase urine for several hours after each dose. SGLT2 inhibitors for diabetes (such as empagliflozin) also increase urine by making the kidneys excrete sugar.

Uncontrolled diabetes

When blood sugar is high, sugar spills into the urine and draws water with it. This causes the classic triad of excessive urination, extreme thirst and weight loss, often with tiredness, blurred vision and genital thrush. In type 1 diabetes this can develop over days to weeks, especially in children, and can lead to diabetic ketoacidosis. In type 2 diabetes it usually develops slowly.

Less common causes

Diabetes insipidus

A rare condition in which the kidneys cannot concentrate urine, causing very large volumes (often 3 to 20 liters a day) of pale, dilute urine and constant thirst, including at night. It is unrelated to blood sugar. Types:

• Central: too little antidiuretic hormone (vasopressin) from the pituitary, after head injury, brain surgery, tumors or with no clear cause. Now also called arginine vasopressin deficiency.
• Nephrogenic: the kidneys do not respond to the hormone, often due to lithium, high calcium or low potassium, or inherited.

See diabetes insipidus.

Primary polydipsia

Drinking excessive amounts of water, either from habit or from a psychiatric condition (psychogenic polydipsia), or from a dry mouth caused by medicines. The urine is dilute because of the intake, not a kidney problem.

Electrolyte problems

• Hypercalcemia: high calcium from overactive parathyroid glands or cancer, with thirst, constipation, kidney stones and confusion.
• Low potassium: from diuretics, vomiting or some hormone disorders.

Kidney causes

Chronic kidney disease, recovery from a blocked urinary tract (post-obstructive diuresis), recovery from acute kidney injury and sickle cell disease can all impair the kidneys' ability to concentrate urine.

Other causes

• Some medicines: lithium, high-dose vitamin D, demeclocycline
• Cold weather (cold diuresis)
• High-protein or high-salt intake, and some tube feeds

Excessive urination at night

Passing large amounts at night (nocturnal polyuria) is common in older adults and in people with heart failure, leg swelling that redistributes at night, sleep apnea, evening fluid or alcohol intake, and poorly controlled diabetes. See excessive urination at night.

How doctors find the cause

A doctor will ask how much you drink and pass, what you drink, when you urinate, about thirst, weight change, medicines (especially diuretics and lithium), head injuries and family history. A bladder diary recording drinks and urine volumes over 2 to 3 days is very useful.

Tests may include:

• urine dipstick for glucose, blood and protein
• blood glucose and HbA1c
• blood sodium, potassium, calcium and kidney function
• urine and blood osmolality (concentration)
• 24-hour urine volume
• a supervised water deprivation test if diabetes insipidus is suspected, sometimes with a copeptin blood test
• pituitary MRI for central diabetes insipidus

Treatment

• Lifestyle: drink to thirst, cut back on caffeine and alcohol, and avoid large drinks in the 2 to 3 hours before bed.
• Diabetes: lifestyle changes, metformin and other medicines, or insulin to bring blood sugar down. Urination returns to normal as sugar levels fall.
• Diabetes insipidus: desmopressin for the central type; for the nephrogenic type, treating the cause, a low-salt diet and thiazide diuretics.
• Electrolyte problems: correcting calcium or potassium and treating the cause.
• Medicines: your doctor may adjust the timing of diuretics, for example taking them in the morning.
• Primary polydipsia: gradual fluid reduction and addressing the reason for excess drinking.

Do not restrict fluids on your own if you have diabetes insipidus, as you can become severely dehydrated.

Frequently asked questions

What is the difference between polyuria and frequent urination?

Polyuria means passing a large total volume of urine, over about 3 liters a day. Frequent urination means going often, usually passing small amounts each time. Polyuria suggests diabetes, diabetes insipidus or high fluid intake. Frequency suggests bladder problems such as infection or an enlarged prostate.

Is excessive urination a sign of diabetes?

It can be. High blood sugar pulls water into the urine, causing large volumes along with thirst, tiredness and weight loss. If you have these symptoms, ask for a blood sugar or HbA1c test. Diabetes is the most common medical cause of polyuria.

How much urination is too much?

For most adults, more than about 3 liters (100 oz) of urine in 24 hours counts as polyuria. Normal output is roughly 0.8 to 2 liters a day, depending on how much you drink. A bladder diary measuring each void is the best way to know.

Can drinking too much water cause excessive urination?

Yes. Healthy kidneys get rid of extra water, so drinking a lot leads to large volumes of pale urine. This is harmless in moderation. Drinking excessive amounts very quickly can dangerously lower blood sodium, so drink to thirst rather than forcing fluids.

Why am I peeing so much at night?

Common reasons include drinking fluids, alcohol or caffeine in the evening, diuretics taken late, leg swelling, heart failure, sleep apnea, uncontrolled diabetes and an enlarged prostate. A bladder diary showing whether night-time volumes are large or small helps identify the cause.