Excessive Urination, Causes

Excessive urination refers to polyuria which is the passing of more than 3 liters of urine in a 24 hour period. A normal feature of polyuria is frequent urination because the human bladder can only hold 300 to 500 ml of urine at full capacity. However, frequent urination should not be confused with polyuria – in urinary frequency, the volume of urine passed out in a day is within a normal range, sometimes even less than the norm for a person.

Causes of Excessive Urination

It must first be differentiated whether the excessive urination is due to increased consumption of fluids. In this instance, drinking excessive amounts of water will read to polyuria and the use of caffeinated drinks or alcohol will further aggravate the problem as these substances act as diuretics. Certain environmental conditions, like cold weather, may result in urinary frequency, however, the quantity of urine passed in a day is usually within the normal range.

• Diabetes mellitus
  • This is the most common cause of excessive urination.
  • Diabetes mellitus is a result of a low levels of insulin or insulin resistance resulting in elevated blood glucose levels (high sugar levels).

• Diabetes insipidus
  • Excessive thirst and urination caused by a deficiency or lack of ADH or the kidney’s resistance to ADH.
  • There are different types of diabetes insipidus which is due to a number of different causes.

• Excessive Thirst
  • Increased thirst (polydipsia) may be physiological, where the thirst center in the hypothalamus is affected, or psychogenic like in anxiety, stress and psychiatric illness.
  • Also refer to Causes of a Dry Mouth.

• Drugs
  • Diuretics act by increasing urine output and this is a desired effect.
  • Side effects of other drugs like lithium, certain antibiotics (e.g. tetracyclines), certain antifungals (e.g. amphotericin B), large quantities of supplements like vitamin D or calcium. Refer to substances causing polyuria for more information.

• Electrolytes
  • Abnormal levels of a  number of electrolytes may result in excessive urination. The cause of these very high or low levels may be due to a number of causes.
  • Hypercalcemia – high levels of calcium in the blood.
  • Hypokalemia – low levels of potassium in the blood.

• IV Saline Drip
  • Excess administration of saline
  • Hypertonic saline

• Other causes
  • Cushing’s syndrome
  • Tube feedings
  • Removal of urinary tract obstruction

Article reviewed by Dr. Greg. Last updated on July 22, 2010