Why is my dog drinking so much water?

How much a healthy dog drinks will change based on factors like their activity level, the foods they eat, and the temperature outside. Sometimes it’s normal for dogs to “tank up,” but alarm bells should go off when they continue to drink excessive amounts of water for no apparent reason.

Continually drinking more water than normal is a symptom of many potentially serious health problems. Let’s take a look at the reasons why dogs might drink a lot of water and what pet parents can do about it.

What is excessive thirst in dogs?

Determining when a dog is drinking more water than normal isn’t as simple as you might expect. As a general rule of thumb, dogs need around ½ - ¾ cups of water per 5 pounds of body weight per day. So, a 20-pound dog would need 2-3 cups of water a day. But this isn’t just the water they drink out of their bowl. It also includes the water in any foods they eat, plus anything they might get elsewhere — like that puddle you had to pull them away from on your morning walk!

Veterinarians define polydipsia (the official term for excessive drinking) as anything over 100 ml per kilogram of body weight per day. This comes out to around 1 cup of water per 5 pounds of body weight. 

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What causes excessive thirst in dogs?

There are many causes of excessive thirst in dogs, including:

Kidney disease

Dogs lose a lot of water in their urine, and drink more to compensate when their kidneys aren’t functioning normally. Other common symptoms of kidney disease include lethargy, poor appetite, and vomiting. Treatment will depend on the type of kidney disease a dog is suffering from. 

Diabetes mellitus

Dogs with diabetes mellitus have high levels of sugar in their blood and urine. This draws water into their urine, leading to dehydration and increased thirst. Other common symptoms of diabetes include increased appetite, weight loss, weakness, recurrent infections, and cataracts. Dogs with diabetes almost always require insulin injections.

Cushing’s disease

Also called hyperadrenocorticism, Cushing’s Disease is caused by abnormally high levels of cortisol. Dogs with Cushing’s Disease usually have increased thirst and urination, a ravenous appetite, a potbellied appearance, and skin and coat problems. Treatment can involve surgery to remove an adrenal tumor or medications to suppress the production of cortisol caused by a pituitary tumor.

Pyometra

Females that have not been spayed are at risk for a potentially life-threatening uterine infection called pyometra. Affected individuals may or may not have vaginal discharge, but they typically drink a lot of water, have a fever, and may vomit. Once a dog’s condition is stabilized, surgery to remove the infected uterus is the best form of treatment.

Liver disease

Liver disease can lead to a buildup of toxic substances in the bloodstream and adversely affect a dog’s kidney function. Dogs will often drink a lot of water to compensate. Treatment will depend on the type of liver disease.

Addison’s disease

Also known as hypoadrenocorticism, Addison’s disease usually develops when the adrenal glands don’t produce adequate amounts of the hormones that help with the management of stress and fluid and electrolyte balance. Dogs may develop vomiting, diarrhea, dehydration, increased thirst and urination, weakness, and collapse. Treatment involves replacing the missing hormones with medications. 

Diabetes insipidus

Antidiuretic hormone (ADH) is produced by the pituitary gland and allows the kidneys to reabsorb water. Dogs will pee out massive amounts of water and drink a lot as a result when their bodies don’t produce enough ADH; this is called CDI, or central diabetes insipidus. They’ll also urinate and drink excessively if their kidneys can’t respond normally to ADH; this is called NDI, or nephrogenic diabetes insipidus. Both of these conditions are rare. CDI can be managed by giving dogs medications containing synthetic antidiuretic hormone. Treatment for NDI should be aimed at any underlying kidney diseases that are present, but medications to reduce urine output and a low-salt diet can help too. 

Primary polydipsia

Some dogs drink more water than normal but appear healthy in all other ways. Primary (also called psychogenic) polydipsia may start with a behavioral or neurological problem, but over time, it can become hard for the kidneys to prevent too much water from leaving the body in urine. Addressing the dog’s behavioral or neurologic issues and gradually reducing the amount of water they drink may help.

Medications and food

Some types of medications, like corticosteroids (prednisone and dexamethasone, for example) and diuretics (such as furosemide and spironolactone), can make dogs urinate and drink excessively. Diets that are very low in protein can increase the amount of water lost in a dog’s urine. Improving a dog’s diet or using the lowest effective dose of a medication should help reduce the amount of water they drink.

Other health problems can also make dogs drink more water than normal. Your veterinarian will need to examine your dog and probably run some tests before they can tell you what might be going on.

When to visit a veterinarian

Most pet parents aren’t in the habit of measuring their dog’s water intake. More typically, we develop a feel for what is normal. How often do we see them drinking? When do we need to fill up the water bowl? It’s time to make an appointment with your veterinarian if you notice persistent changes in how much your dog might be drinking, particularly if they’re also showing any other symptoms of illness, including:

• Increased urination

• Problems urinating

• Appetite changes

• Weight loss or gain

• Lethargy

• Weakness

• Vomiting

• Diarrhea 

Diagnosis and treatment

Your veterinarian will start the diagnostic process by taking a complete health history, performing a physical exam, and trying to confirm that your dog is indeed drinking more water than normal. They may ask you to measure your dog’s water intake at home, but if this is not possible, they can perform a simple test called a urine specific gravity (USG) to see if your dog is producing dilute urine (urine with a lot of water in it).

If your dog has multiple low USG measurements taken over several days or has other symptoms of illness, there is likely a problem. The vet will then start looking for the more common reasons why dogs drink a lot of water. They will probably run a urinalysis, complete blood count, and blood chemistry profile. If this hasn’t led to an answer, specific testing for Cushing’s Disease or Addison’s Disease may be needed.

When everything else has been ruled out, the veterinarian may recommend a water deprivation test and an ADH response test to determine if a dog has central diabetes insipidus, nephrogenic diabetes insipidus, or primary polydipsia.

Treatment for a dog that drinks excessively should always be focused on their underlying health problem. Never take water away from a dog who is drinking more than normal. They can become dangerously dehydrated very quickly.

Prevention and at-home care

In most cases, successfully treating or at least managing the cause of a dog’s excessive thirst will result in them drinking less. Follow your dog’s treatment plan and call your veterinarian for advice if it doesn’t seem to be working as well as expected. 

Providing dogs with a nutritious diet, ample exercise, a safe environment, and staying up-to-date on wellness care will go a long way toward keeping them happy and healthy. And since we can’t prevent all the causes of polydipsia (or other health problems!), it makes sense to look into a good dog insurance plan to help you pay for any veterinary care your dog might need.