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Polydipsia is the medical term for extreme thirst that a person cannot quench by drinking.

It is not a disease but a symptom of certain health problems, such as diabetes. People who have this symptom should see a doctor.

In this article, we look at what polydipsia is and how to manage it.

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Persistent thirst may be due to polydipsia.

When a person feels thirsty after eating salty food, doing strenuous exercise, or spending time in the sun, they can usually quench their thirst by drinking more fluid.

The amount of water that a person needs depends on various factors, including how active they are and the climate in which they live.

Polydipsia is a type of thirst that can last for days, weeks, or even longer, depending on the cause. The person will feel thirsty most or all of the time, and they will not be able to quench their thirst, however much they drink. They may also have a dry mouth.

A person with polydipsia will drink 6 liters (L) or more of fluid a day.

Polyuria, which is frequent urination, usually accompanies polydipsia. A doctor is likely to say that an adult has polyuria if they pass at least 2.5 L of urine in 24 hours.

Learn more here about frequent urination.

Some factors that may cause a person to feel more thirsty than usual include:

  • high blood sugar levels due to diabetes mellitus
  • diabetic ketoacidosis (DKA), a complication of hyperglycemia due to diabetes mellitus
  • low vasopressin levels as a result of diabetes insipidus, a rare condition
  • dehydration
  • a loss of bodily fluids, for example, through sweating, diarrhea, or vomiting
  • the use of certain medications
  • having an uncomfortably dry mouth

Polydipsia is a common symptom of high blood sugar levels. It can be an early sign of type 1 diabetes or can indicate that a person with diabetes is having difficulty managing their condition.

Diabetes mellitus

Insulin helps glucose enter the cells, which use it for energy. In a person with diabetes mellitus, the body either does not produce insulin or is not able to use it effectively.

As a result, glucose from food remains in the blood instead of entering the cells, and this leads to disruption in the body.

The kidneys have to work harder to filter the unwanted sugar out of the blood. As the body excretes the sugar into the urine, it takes fluid with it. This loss of fluid causes the person to feel thirsty, so they drink and urinate more.

Common symptoms of high blood sugar levels include:

  • polydipsia
  • polyuria
  • extreme hunger
  • blurred vision
  • fatigue and lack of energy
  • unexplained weight loss or gain

The person may start to notice that they are more prone to infections and that it takes longer for wounds to heal. In time, further complications can arise, such as high blood pressure and cardiovascular disease.

What are the features of type 1 and type 2 diabetes? Learn more here.

Diabetic ketoacidosis (DKA)

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If a person with diabetes starts to feel more thirsty than usual, they should check their blood sugar levels.

When a person has diabetes and glucose cannot enter the cells to provide energy, the body may start to break down fat for this purpose.

This process produces a toxic byproduct called ketones. If ketones build up in the blood, they can cause it to become too acidic. This change in pH can lead to DKA, which can potentially be fatal.

The early symptoms of DKA are extreme thirst and a frequent need to urinate. A person who has these symptoms should test their blood sugar levels. If these are at 240 milligrams per deciliter or above, the person should check their urine for ketones.

Later symptoms may include

  • a fruity or “acetone” smell on the breath
  • tiredness
  • dry or flushed skin
  • difficulty concentrating
  • confusion
  • difficulty breathing
  • nausea and vomiting
  • abdominal pain
  • loss of consciousness
  • coma

Anyone who has these symptoms should seek emergency medical help as the condition can rapidly become severe and even life-threatening.

Kits for testing ketone levels and blood sugar levels are available for purchase online.

Diabetes insipidus

This form of diabetes is a rare condition that affects one in 25,000 people. It is different from diabetes mellitus, and it does not involve a problem with insulin.

There are different types of diabetes insipidus, each with a different cause. However, they all involve a problem with vasopressin, an antidiuretic hormone that helps control fluid removal through the kidneys.

A person with diabetes insipidus may pass large volumes of clear, odorless urine. According to the National Institute of Diabetes and Digestive and Kidney Diseases, they may pass between 3 and 20 quarts (about 3.4–22.7 L) of urine a day.

These individuals may report polydipsia. Rarely, severe dehydration can also occur.

Dehydration symptoms include:

  • thirst
  • dry skin or eyes
  • tiredness
  • nausea

Even if a person does not think that they are dehydrated, they should seek immediate medical help if they experience the following symptoms:

  • sluggishness
  • dizziness
  • confusion

Click here to learn more about diabetes insipidus.

Mental health conditions

In a 2013 study, researchers looked at excessive thirst or liquid consumption in people attending an outpatient clinic for mental health conditions.

Of these people, 15.7% had primary polydipsia, an excessive thirst that is not due to the use of medication or another identifiable cause. In this subgroup, 13 people had schizophrenia, and one person had bipolar disorder.

Medications that doctors prescribe for these and other conditions can also increase thirst.

Reasons that the participants gave for drinking a lot included having a dry mouth, believing that drinking water keeps the body clean, doing it out of habit, and trying to cope with feeling empty.

The authors of a 2017 study concluded that polydipsia had features in common with obsessive-compulsive disorder (OCD). For example, the person is often not aware that their fluid consumption is excessive.

The researchers suggested that there may be a neurobiological link between these conditions and proposed a traumatic brain injury as one possible cause of polydipsia.

When the cause of drinking too much is psychological, there is a risk of water intoxication, which can be dangerous. Researchers do not yet know precisely why polydipsia happens. Scientists have called for further studies to find out more.

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The doctor may order tests to identify the cause of polydipsia.

Anyone who develops extreme thirst without a known cause should see a doctor because it may be a sign of diabetes.

If the person has not already measured how much fluid they are drinking each day and how much urine they are producing, the doctor might ask them to do this.

A person can work out how much fluid they are drinking by starting the day with a measured container of water and then drinking only from that container, refilling it throughout the day and noting how much fluid they drink in 24 hours.

They should also factor in any other liquid, such as fruit juice and coffee, that they consume within the period.

To measure urine output, a person can use a special container for collection.

If the person already has a diagnosis of type 1 or type 2 diabetes, they should check their blood sugar levels first. They may be able to resolve slightly high glucose levels by doing some exercise or taking insulin, if appropriate.

If the thirst persists or gets worse, they should see a doctor. It could indicate that they need treatment for DKA, or they may need to adjust their treatment plan.

Keeping a record of the extent of the thirst, fluid intake, and blood sugar levels can help the doctor decide what to do next.

The doctor may order blood and urine tests to check blood sugar levels and help identify the cause of the symptoms.

If blood sugar levels are normal, the doctor may suggest other tests to check for:

  • low vasopressin levels
  • an imbalance of sodium and potassium in the blood
  • fluid deprivation

Some drugs may cause or worsen polydipsia and polyuria. For this reason, people should take a list of all of their current medications with them when they visit the doctor.

The type of treatment will depend on the underlying cause.

Diabetes mellitus

The main aim of treatment will be to keep blood sugar levels within a specific target range. A person with type 1 diabetes will need to use insulin.

In the case of type 2 diabetes, most people will start by using lifestyle measures, such as changes to their diet and exercise regimen, to manage their blood glucose.

The doctor may also prescribe insulin, metformin, or another medication.

Managing blood sugar levels should resolve the symptoms of polydipsia.

DKA

The person may need treatment in the hospital to replace lost fluid and electrolytes. This treatment may include intravenous insulin and rehydration fluids.

Diabetes insipidus

The doctor will advise the person to consume enough water to prevent dehydration, and they may also prescribe medications, such as desmopressin, which is a synthetic form of vasopressin.

Medication-induced polydipsia

If a person’s medications are causing excessive thirst, the doctor may amend their prescription to switch a medication or alter its dosage.

Mental health conditions

Counseling can help a person become aware of how much fluid they are drinking and adjust their intake, if necessary.

The doctor may also change the person’s medication or take other measures if there is a physical cause.

Early recognition and treatment of polydipsia can lead to a diagnosis of diabetes or another health problem.

Whatever the cause, it is usually possible to resolve polydipsia with treatment. However, if this symptom is an early indication of diabetes mellitus or diabetes insipidus, the person may need treatment for life.