There are many reasons for excessive thirst. Polydipsia is a common symptom for many normal activities, including:

• Exercise
• Loss of fluids, possibly by excessive sweating
• Consuming spicy or salty foods, alcohol or caffeine

Certain medications can also result in the body craving more fluids, including:

• Diuretics. Medications that stimulate the creation and release of urine in an effort to reduce the amount of body fluid. Diuretics are often prescribed to treat conditions such as high blood pressure, heart failure or edema. However, diuretics can raise glucose (blood sugar) levels, so close monitoring of glucose is important for people who have diabetes mellitus. Diuretics are also prescribed for some patients diagnosed with diabetes insipidus.
  
  
• Anticholinergics. Medications that open bronchial tubes to improve breathing and help clear mucus from the airways. They are primarily used in the treatment of asthma or other breathing problems. Some forms of this medication also work as antispasmodics, relieving cramps or stomach spasms. They may be recommended for the treatment of gastrointestinal problems or the prevention of nausea and motion sickness.
  
  
• Antiarrhythmics. Medications to correct abnormal heartbeats.
  
  
• Chemotherapy drugs. Medications used to treat cancer.
  
  
• Many psychiatric medications. Antipsychotics, lithium and tricyclic antidepressants, for example, can dry the mouth.
  
  
• Many gastrointestinal medications. In addition to antispasmotics, GI medications that can dry the mouth include antidiarrheals, antiemetics and proton pump inhibitors.
  
  
• Demeclocycline. An antibiotic used to treat bacterial infections and low levels of sodium (hyponatremia).
  

However, polydipsia can also be a sign of a more serious underlying problem. Polydipsia and polyuria are not specific to any one disease, but rather are factors in several conditions, including:

• Dehydration. A reduced level of water in the body. The many causes of dehydration include sweating, vomiting, diarrhea, fever, hot flashes, sunburn, excessive dieting, anorexia nervosa and blood loss. Any of these can, in turn, lead to increased thirst.
  
  
• Hyperglycemia or prediabetes. Higher-than-normal blood glucose levels. Excessive urination and increased thirst are possible symptoms.
  
  
• Diabetes mellitus (DM or “sugar diabetes”). A disorder of the body’s ability to use blood glucose. Two main symptoms are excessive thirst and urination. This type of diabetes includes type 1 and type 2 diabetes.
  
  Dangerous conditions involving severe hyperglycemia, including diabetic ketoacidosis and hyperosmolar hyperglycemic nonketotic syndrome, may be marked by extreme polydipsia.
  
  
• Diabetes insipidus (DI or “water diabetes”). An uncommon disorder in which the kidneys cannot conserve water, usually because of damage to the pituitary gland or a part of the brain called the hypothalamus. DI and DM have some symptoms in common but are unrelated conditions. DI causes the body to produce large amounts of diluted urine, which in turn leads to an imbalance in the body’s water level. With the increased depletion of water, excessive thirst is a common symptom of DI.
  
  
• • Other endocrine disorders. Any disease or disorder of the endocrine system, which is responsible for reproduction, growth, internal balance of body systems and the production of hormones. Too much or too little of any hormone can cause problems in the body. Frequent and excessive thirst are common symptoms for many of these disorders, including:
    
    
  • Overactive adrenal glands (hyperadrenalism or Cushing’s disease). Disease in one or both of the adrenal glands, which are located atop the kidneys, can lead to an overactivity of the adrenal glands. As part of their major role in the endocrine system, the adrenal glands secrete the hormones cortisol and aldosterone. These adrenal disorders often show symptoms of increased thirst and urination, among others.
    
    
  • Overactive parathyroid glands (hyperparathyroidism). The parathyroid glands release hormones into the bloodstream that regulate the amount of calcium, phosphorous and magnesium going to the bones and blood. If calcium levels get too high, a host of symptoms, including vomiting and polyuria, can lead to excessive thirst.
    
    
• Wolfram syndrome. A rare genetic disorder that includes diabetes mellitus and diabetes insipidus.
  
  
• Kidney disorders. Any disease or disorder of the kidneys, such as diabetic nephropathy. The kidneys clean the blood and keep blood chemicals balanced. Many kidney conditions can result in an increased level of urination and thus result in polydipsia.
  
  
• Dry mouth (xerostomia). The many conditions that can cause dry mouth include Alzheimer’s disease, burning mouth syndrome, HIV/AIDS, hypothyroidism, Parkinson’s disease, sarcoidosis (disease in which small lumps form in organs), Sjogren’s syndrome (an autoimmune disorder) and smoking.
   
• High blood calcium (hypercalcemia). Though calcium is by far the most prevalent mineral in the body, when blood calcium is high, it can be a sign of disease. It also can cause constipation, increased thirst and urination, nausea, vomiting, irritability, kidney failure, psychosis and coma.
  
  
• High blood sodium (hypernatremia) or low blood potassium (hypokalemia). Certain minerals are needed in a person’s diet to maintain health. But when sodium is high or potassium low, the body may desire more water. Mineral imbalances can also be a result of taking certain medications.
  
  
• Liver disease. The liver is involved in many functions including maintaining chemical balance, removing toxins and making bile to aid in digestion. There are numerous diseases and disorders of the liver, many of which can lead to the liver malfunctioning or possibly even shutting down. Some of the more common liver diseases include cirrhosis, hepatitis and disease due to alcohol. Symptoms may include nausea, dry mouth and excessive thirst.
  
  
• Excessive bleeding. Bleeding disorders can result in a decrease in blood volume. This loss of body fluids often results in dehydration, which leads to an intensified thirst. Such disorders may involve:
  
  
• • Gastrointestinal bleeding
  • Blood loss from any wound severe enough to cause heavy bleeding (hemorrhage)
  • Heavy menstrual bleeding
    
    
• Severe infections or burns. Severe infections can lead to fever, vomiting and diarrhea. Dehydration or excessive thirst resulting from a burn requires prompt medical attention.
  
  
• Urinary tract infections. An infection that develops along the urinary tract, including the kidneys (nephritis), bladder (cystitis) or the tubes leading between them (the ureters) or out of the body (the urethra). Common symptoms include painful urination and three conditions that can lead to increased thirst: fever, vomiting and sometimes diarrhea.
  
  
• Drug abuse. The use of some illegal drugs, such as ecstasy, has been shown to cause excessive thirst.
  
  
• Head injury. Any trauma to the brain, whether or not there is damage, is considered a head injury. Vomiting, which is a common after-effect of a head injury, can lead to excessive thirst.
  
  
• Psychogenic polydipsia. A psychological disorder that leads to compulsive water drinking. It may occur with schizophrenia or obsessive compulsive disorders.