What Is Polydipsia?

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Polydipsia is drinking a large amount of fluid, most often water, in response to extreme thirst, though there can be other reasons for this. Thirst is your body's way of correcting fluid balance that can occur due to factors like dehydration. Several medical illnesses, most notably diabetes mellitus, can cause polydipsia. Often, polydipsia due to disease is associated with polyuria, which is frequent urination.

If you have noticed that you feel the need to drink more than usual or more than is typically advised, be sure to talk to your doctor. Timely diagnosis and treatment of a medical condition, if present, can help correct the problem and prevent it from progressing.

Types and Causes

Primary polydipsia is a condition that involves drinking more water than your body needs or should have.

Secondary polydipsia is drinking excess water due to disease-induced or medication-induced thirst prompted by an actual need for water.

Secondary Polydipsia

Since secondary polydipsia is actually the more common of the two, let's start there.

Your body uses a variety of mechanisms to ensure that you have the right amount and concentration of water in your blood, organs, and cells. Arginine vasopressin (AVP) is a hormone that helps manage that fluid balance. It sends signals to your kidneys to regulate water concentration in your urine, and it sends signals to your brain to mediate thirst.

Medical issues that disrupt any step in this process or alter AVP can cause or contribute to polydipsia.

Illness, Sweating, and Under-Hydration

Dehydration is the most common cause of secondary polydipsia. Sweating, fevers, vomiting, diarrhea, or just not getting enough to drink can dehydrate you. You might experience extreme thirst and polydipsia (without polyuria) for a few days as you are recovering from an infection.

Polydipsia stemming from dehydration caused by such concerns is typically short term. If you listen to your body and drink fluids when you are thirsty, you can effectively replenish yourself. In fact, it's only when you are too weak to drink that things can get dangerous.

If you are dehydrated but can't drink, you could actually need fluid supplementation intravenously (IV, in a vein).

Diabetes Mellitus

Type I and type 2 diabetes mellitus are the most common causes of chronic polydipsia. They, too, are related to dehydration, but of a chronic kind.

Both of these cause elevations in blood glucose (sugar). To protect itself from the harmful effects of excess glucose, you eliminate it in your urine. Because of the way the kidneys function, excess water flows into the urine to help this, which is what can lead to dehydration.

In an attempt to combat fluid loss, your body sends signals telling your brain that you need to drink, and you start to get thirsty. This is compensatory polydipsia: Your body is making you thirsty to try to correct the dehydration.

With diabetes mellitus, recurrent dehydration means almost constant thirst; polydipsia with polyuria are very common effects.

Diabetes Insipidus

Diabetes insipidus can be associated with altered production or response to hormones, including AVP.

With this condition, the body makes excessively large amounts of urine, which can also cause dehydration. Compensatory polydipsia may develop as the body signals the brain to drink fluids to correct for this.

Unlike diabetes mellitus, diabetes insipidus has nothing to do with blood glucose. Sometimes the disease is genetic, and sometimes it is acquired.

The condition can develop due to kidney problems. For example, Sjögren's sydrome can affect the kidneys, causing nephrogenic diabetes insipidus. Central diabetes insipidus also occurs when fluid-controlling hormones are disrupted due to damage of the pituitary gland or the hypothalamus in the brain (from an injury after surgery).

Other Medical Causes

Diseases that disrupt your electrolyte levels can sometimes lead to polydipsia (with or without polyuria). For example, abnormal potassium or sodium levels can trigger thirst as your body attempts to balance their concentration.

Some medical conditions that can cause polydipsia include:

Medications

A number of over-the-counter or prescription medications can make you feel thirsty and might lead to polydipsia as well. Several medications induce polydipsia due to dehydration and compensatory mechanisms, and some just induce thirst because of side effects like a dry mouth.

Diuretics, often called "water pills," are used to lower blood pressure. They induce urination, which typically causes compensatory thirst. And laxatives, which help relieve constipation, often result in mild dehydration that triggers thirst.

Some medications make you thirsty even without dehydrating you. One such example: anticholinergic antidepressants.

Primary Polydipsia

Primary polydipsia is a condition characterized by excessive fluid intake without underlying dehydration. This means that increased water intake is not the result of your body trying to correct a fluid imbalance.

A person might drink an excessive amount of fluid because they thought it was healthy, or because a health professional told them to drink "plenty of fluids" (but that was not defined). Some people have been known to drink too much plain water when participating in sporting events.

Cases of personal decisions aside, there are two other possible causes of primary polydipsia, both of which have medical underpinnings.

Psychogenic polydipsia is a behavioral issue that often occurs with schizophrenia. Those with it feel the need to drink, though there is no physiological reason for it. It’s unclear exactly why this happens, and some psychiatric medications may worsen the problem.

Less commonly, certain types of brain dysfunction can cause another type of primary polydipsia called dipsogenic polydipsia. This can happen when the hypothalamus (the part of the brain involved in thirst) is injured. The condition might make you feel thirsty, even though your body doesn't need more water.

Dipsogenic polydipsia can seem similar to some types of diabetes insipidus, but the latter is a response to dehydration, and there are key differences in hormone and electrolyte levels.

How Much Water Do You Really Need?

A healthy adult should consume an average of two liters of water per day (that's eight glasses, averaging eight ounces each). However, you might need more if you're larger than the average healthy adult (137 pounds), as well as when you exercise or spend time in a hot environment.

Polydipsia Symptoms

It might take a few weeks or even longer for you to realize that you have chronic polydipsia. Depending on the underlying cause, it can begin abruptly or develop gradually over time.

Day-to-day effects include:

  • Feeling extremely thirsty even if you’ve been drinking a lot of water or other fluids
  • Frequently on the lookout for a drinking fountain or asking for many drink refills at restaurants
  • A constantly dry mouth or dry lips or skin

With polyuria, you might make many trips to the bathroom or you may have a noticeably large volume of urine whenever you go.

Associated Symptoms

Polydipsia is often associated with additional symptoms stemming from its medical cause.

For example, you can have fatigue with type 1 diabetes mellitus. Children with this condition may wet the bed, and that can be the first sign that parents notice. With type 2 diabetes mellitus, you might experience unexplained weight loss.

Some conditions associated with polydipsia can cause dizziness, trouble concentrating, or changes in appetite.

If the underlying cause of polydipsia progresses without treatment, severe health problems—like confusion or loss of consciousness—can occur.

Complications

If you go overboard in drinking water in response to primary polydipsia, water intoxication or hyponatremia can occur. Though rare, these are potentially life-threatening issues that can lead to:

  • Nausea and vomiting
  • Headache
  • Confusion and delirium
  • Seizures
  • Coma

Excess water intake isn't typically dangerous when you have secondary polydipsia. Rather, it's the underlying disease that's causing polydipsia that is the concern.

However, fluid balance is a precisely regulated function that involves the kidneys, adrenal hormones, hypothalamus, blood pressure, and heart rate. As such, secondary polydipsia can cause harm due to overhydration in cases when it overwhelms the kidneys' ability to eliminate water in the urine. This is rare.

If you have severe kidney disease or dysfunction of your fluid-regulating hormones, you can develop consequences of over and/or under hydration from either type of polydipsia.

Diagnosis

If you have polydipsia with or without polyuria, your doctor will evaluate you to see if you have an underlying medical condition. They will ask you about the amount of fluid you drink and how often and how much you urinate. Your doctor will also review your medication list and do a physical exam.

Keep in mind that it is really hard to accurately gauge fluid intake and urination—so if you can't estimate these amounts correctly, don't worry. Basic laboratory blood and urine tests are a key part of the diagnosis.

You might also need an imaging test so your doctors can visualize your kidneys or brain if there is concern about a structural problem.

You might need some of the following blood tests:

Urine Tests

Urine tests can detect glucose (a sign of diabetes mellitus) and can give your doctor a measure of how concentrated your urine is. That can help differentiate between primary polydipsia and compensatory polydipsia.

Generally, primary polydipsia is associated with a very low urine electrolyte concentration, while polydipsia caused by medical problems is usually associated with normal or high urine concentration.

Urine Volume

Measurement of your daily urine volume might be necessary if there are still unanswered questions based on your blood tests and urinalysis results. As you can probably guess, this can be somewhat tedious, however, so it is not a standard way of evaluating polydipsia.

An average adult produces 1.5 liters of urine per day.

Water Deprivation Test

A water deprivation test is a specialized diagnostic test that shows how your body responds to an injection of AVP after drinking less water. This test would involve reducing your water intake and going into your doctor's office for an injection—and then staying for several hours so you can have your test.

If you don't have any problems evident in your blood or urine tests, it is likely that your fluid consumption is just due to a personal need to drink a lot to stay hydrated, rather than a medical concern. Still, your doctor may recommend a follow-up test in six to 12 months to monitor for early signs of diabetes, just in case.

Treatment

Treatment for polydipsia depends on the underlying medical condition.

If you have been excessively thirsty, don't limit your fluid intake without talking to your doctor first. Treatment for secondary polydipsia is focused on alleviating the disease, not on reducing fluid intake, and you could make things worse by cutting back. Reducing your fluid intake is only a strategy for managing primary polydipsia.

Once a condition is identified and treated, you will likely need close follow up. The hormonal regulation at play when you have diabetes, adrenal disease, or hypothalamic conditions can be somewhat unstable. You may need to be periodically monitored and have your treatment adjusted over the years.

Your doctor will let you know what signs you need to look out for as you evaluate the effects of any treatment. For example, a child who is bedwetting due to diabetes mellitus might improve once treatment is started—and the recurrence of this problem can signal inadequate management.

Behavioral

For primary polydipsia, the key is modifying your fluid intake so you can start drinking a healthy amount. If you have misunderstood the amount of fluid that you should be drinking to stay healthy, your doctor or a dietitian can help you. You can measure out your water for the day to help yourself adjust. Some like to use water bottles with measurements printed on them.

Fluid moderation can be a challenge for people with serious psychiatric symptoms. Generally, a person who has polydipsia due to a psychiatric disease like schizophrenia also has other serious psychiatric symptoms that interfere with insight and ability to moderate behavior like fluid intake. In some cases, a change in psychiatric medication or behavioral therapy might be helpful.

Dialysis

While it is rare that secondary polydipsia can cause overhydration beyond that which your body can compensate for, you might need dialysis if your kidneys can't balance your fluids.

Keep in mind that dialysis is not a treatment specifically for polydipsia—it is a treatment for kidney failure, whether you drink large amounts or not.

A Word From Verywell

Polydipsia is a symptom of a variety of different medical conditions. It might be a side effect of one of your medications or it can be a sign of an undiagnosed medical illness. If you or your child has this problem, be sure to talk to your doctor so you can get it taken care of.

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