An Overview of Polyuria

Polyuria is a medical term that describes excessive urination. Outside of drinking an unusually excessive amount of water, excessive urination could indicate underlying medical conditions. The most common causes of polyuria are diabetes mellitus and diabetes insipidus. In addition, polyuria can be caused by medications, caffeine, alcohol, kidney disease, and electrolyte imbalance.

Urine is created in the kidneys with water and solids filtered from the bloodstream. Each adult should void no more than 2.5 liters of urine daily. Polyuria occurs when an adult produces more than 3 liters, regardless of how often he or she urinates. Frequent urination is a different issue and may or may not be associated with polyuria or nocturia, which is urination at night when a person should be sleeping.

The prevalence of polyuria is not very well documented. Nocturia has been studied more than polyuria. There is evidence suggesting that nocturia and polyuria are both more common in older patients.

Polyuria literally translates to "urinating too much" and may be the only symptom one experiences. However, depending on the cause, there are other symptoms that can accompany polyuria. When the cause is either diabetes insipidus or diabetes mellitus, polyuria is usually coupled with excessive thirst (polydipsia).

Frequent urination, especially at night (nocturia), is often associated with polyuria but doesn't have to be.

There are myriad causes of polyuria that range from being as simple as drinking too much water to a serious health complication like kidney failure. The following causes of polyuria are the most common.

Diabetes mellitus is a condition caused by the body's inability to adequately control blood sugar, either because it is unable to properly manufacture insulin or a resistance to the effects of insulin. Diabetes mellitus leads to higher osmolarity in the bloodstream because of increased sugar levels.

Diabetes insipidus is completely different from diabetes mellitus and doesn't have anything to do with blood glucose levels. Instead, diabetes insipidus is related to polyuria directly as it relates to arginine vasopressin (AVP), an antidiuretic hormone.

Central diabetes insipidus is caused by a lack of arginine vasopressin secretion due to a neurological condition. Nephrogenic diabetes insipidus is due to failure of the kidney to respond to AVP. Central diabetes insipidus can be acquired from a medical or traumatic brain injury. Nephrogenic diabetes insipidus is usually inherited.

Certain medications are designed to increase urination to treat conditions like congestive heart failure and high blood pressure. Those medications can lead to polyuria if the dosages are not correct. Your physician will adjust the dosing of the medications as necessary to avoid unnecessary urination.

Lithium is a medication used to control mood disorders. It is almost entirely excreted from the body in urine and can have a profound effect on the kidneys in patients who take it regularly. Lithium can cause polyuria and polydipsia as a result of lithium-induced nephrogenic diabetes insipidus.

However, if polyuria is present and lithium is not discontinued, irreversible damage to the kidneys can cause permanent polyuria.

Both alcohol and caffeine have known diuretic effects. Drinking either one to excess is capable of triggering polyuria to the point of developing dehydration in the patient. Alcohol is always a diuretic, even to people who drink alcohol on a regular basis. The diuretic effects of caffeine can decrease over time in people who regularly drink it.

Polyuria is a symptom rather than a medical condition in its own right. There is no actual diagnosis of polyuria. However, the underlying cause of polyuria can be diagnosed once the symptom appears. The process of diagnosis for each cause is different. In every case, the physician will begin with determining the time of onset of the polyuria and whether it came on suddenly or gradually over time.

If the onset of polyuria follows a significant neurological issue such as traumatic brain injury or stroke, it could be a symptom of central diabetes insipidus.

Polyuria and polydipsia are both signs of diabetes mellitus as well as diabetes insipidus. Both conditions are significant and require further tests. The physician will want to measure the patient's A1C, a blood test that retroactively measures the average blood glucose levels over the previous six months.

The physician most likely will also order a urine glucose test to see if the body is excreting sugar in the urine, a sign of diabetes mellitus.

The most effective treatment for polyuria is aimed at the underlying cause. For example, lithium-induced nephrogenic diabetes insipidus could potentially be treated by discontinuing the lithium. Polyuria caused by diabetes mellitus is likely to be improved once the patient's blood glucose levels are under control.

Polyuria that cannot be corrected by treating the underlying cause is often treated with one of several medications that come from many different classes. One hallmark of polyuria is the diluted nature of the urine produced—it's composed of more water than urine.

Some treatments for polyuria include giving a type of diuretic, which usually increases urine output because it improves the way urine is processed in the kidneys.

If you suspect that you are urinating too much (or too often), it's time to contact your primary physician, especially if you are also always thirsty. Polyuria can be treated and in the short term is not dangerous. However, it's crucial to get it corrected so any potential underlying condition doesn't go untreated. Rest assured that early intervention with polyuria, as with any health condition, is key to managing and treating your health in the best way possible.