There are many potential causes of polydipsia. The underlying cause of a patient’s symptoms must be determined before an appropriate treatment, if any, can be started.

A physician will most likely take the patient’s medical history and perform a physical examination, as well as determine a time line and possible pattern for the excessive thirst.

Additional questions may be asked regarding the patient’s history and lifestyle, including:

• Eating and exercise habits
• Recent illnesses
• Recent weight loss or gain

If normal activities or causes can be ruled out, then diagnostic testing may be recommended, including:

• Urine tests:
  
  
• • Urine specific gravity test. Shows how well the kidneys are processing varying amounts of water in the urine.
    

    

• • Urine osmolality. Shows the concentration particles of the urine and is a more exact measurement of urine than the specific gravity test.
    
    
• Blood tests:
  
  
• • Blood differential. Shows the number and type of white blood cells in the blood as well as providing valuable information on possible infections, allergies, parasites and more.
    
    
  • Serum calcium. Shows the level of calcium in serum (the liquid part of blood without blood cells). This blood test is often used to screen for diseases of the parathyroid gland, kidneys and bone.
    
    
  • Blood glucose level. Shows the level of sugar in the blood, an important test to diagnose diabetes mellitus and a vital management tool for people with diabetes.
    
    
  • Serum osmolality. Shows the comparison of water to chemical substances dissolved in the blood. Increased serum osmolality (hyperosmolality) is seen in a number of conditions, including diabetes insipidus and diabetes mellitus.
    
    
• Water deprivation test. Shows the presence of the four major forms of diabetes insipidus (gestagenic, neurogenic, nephrogenic and polydipsic) by testing the body’s ability to concentrate urine when the patient has no water to drink for at least eight hours. Weight and plasma measurements are taken at specified intervals after the patient is allowed to drink as usual.