The short answer: An older dog that starts drinking more than before nearly always urinates more too. Heat, exercise, salty food and cortisone treatment can explain it. Without such an explanation, the most common causes in an older dog are womb infection in unspayed females, Cushing's disease, diabetes, reduced kidney function and liver disease. Measure the water over 24 hours: more than 100 ml per kilo of body weight is too much. An unspayed female that drinks a lot and is tired after her season should see a vet the same day.
How much should a dog drink?
AniCura gives a normal fluid requirement of about 50 ml per kilo of body weight per day3, Agria 50 to 100 ml1. A 20 kg dog therefore normally drinks around one litre. The limit for too much is the same at Agria and Evidensia: over 100 ml per kilo per day12. For the same 20 kg dog, that means more than two litres.
Heat, exercise and salty food can raise thirst temporarily1. A dog that switches from wet food to dry food drinks more. A hot summer day shows straight away in the water bowl. What should make you react is an increase that persists without anything like that having changed.
How to measure
Fill a large bowl with a measured amount of water. After 24 hours, subtract what is left. If the bowl runs out, top it up with measured amounts and count them2. Divide the total by the dog's weight. Measure for two or three days if you can. Water drunk on walks is not counted, but note whether the dog seeks out puddles and lakes more than before.
Bring a urine sample if you can. Morning urine is best. Catch the middle of the stream, not the beginning or end. A flat bowl works for large dogs and a lid or similar for small ones2.
Five common causes in older dogs
1. Womb infection (pyometra). The most urgent cause. It affects unspayed females, mainly middle-aged and older, and signs usually appear in the weeks after a season1. It is common: in a study of insured dogs in Sweden, on average 23 to 24 percent of females had had pyometra by the age of ten4. Typical signs are increased thirst, tiredness, poor appetite, fever and vaginal discharge5. But there is no discharge if the cervix is closed. Then increased thirst and tiredness may be all you see1. The disease can lead to sepsis and is usually treated with surgery5.
2. Cushing's disease. The body produces too much of the stress hormone cortisol. It is seen mostly in middle-aged to older dogs. Besides thirst, increased appetite, hair loss, poor stamina and muscle weakness are common signs2. Diagnosis requires special hormone tests. According to the consensus statement of the American College of Veterinary Internal Medicine (ACVIM), none of the tests is perfect, so they should only be done when the dog has signs that fit6.
3. Diabetes. Most common in middle-aged and older dogs. The typical pattern is a dog that drinks and urinates more, eats more and still loses weight12. Treatment is insulin and weight control, managed together with your vet.
4. Reduced kidney function. When the kidneys no longer concentrate urine, the dog passes more water and drinks to compensate. Over time, poorer general condition, reduced appetite, weight loss and vomiting may follow2. Kidney values are interpreted the same way as in cats, with somewhat different limits. We explain how in our article on high kidney values in cats.
5. Liver disease. Can cause increased thirst together with poorer general condition, weight loss and gastrointestinal problems2.
Other causes your vet will consider are urinary tract infection, pain, fever and raised calcium in the blood, which can occur with some cancers among other things13. If the dog is on cortisone, increased thirst is a common side effect that usually passes when the course ends3.
Key insight: Sex and neutering are the first sort. In an unspayed female, pyometra is the diagnosis to rule out first, the same day. In other older dogs, appetite gives the next clue: more thirst and more hunger points towards Cushing's or diabetes, more thirst and poorer appetite more often towards the kidneys or liver.
What the vet does
The work-up starts with questions and an examination. Then come a urine test for concentration, sugar and infection, and blood tests for kidneys, liver and blood sugar12. If pyometra is suspected, an ultrasound or X-ray of the abdomen is done. Hormone tests for Cushing's come later, when the simpler tests point that way1. Expect it to take more than one visit before the cause is clear.
When to see the vet
The same day or as an emergency if an unspayed female drinks a lot and is also tired, off her food, has discharge, fever or a swollen abdomen, especially in the weeks after a season1. It is also an emergency if a dog drinks a lot and vomits repeatedly, refuses food or seems to be in pain. If you are unsure, call a veterinary advice line or your local emergency clinic.
Within a few days if the dog drinks and urinates more than usual but otherwise eats and behaves normally, or if it has started leaking urine or urinating indoors. Evidensia recommends booking an appointment even if the dog otherwise seems healthy2.
What you can do yourself
Keep water available. It is tempting to ration water when the dog urinates indoors, but a dog drinking to replace lost fluid will become dehydrated if it is denied water2. Go out more often instead, including late in the evening.
Measure, weigh and take notes. Water per day, weight, appetite, any recent season and which medicines the dog takes. It shortens the work-up.
Watch the salt. Chews, treats and table scraps can be salty. Pause them while you measure, so you know what you are measuring.
Book a health check for your older dog. A blood and urine test once a year often catches changes before they show in the water bowl.
Related product
NEPHTANNU Pet Syrup. A syrup with seven herbs that have a long tradition in kidney function and fluid balance, made as a complementary feed for older dogs and cats. It does not explain why your dog is drinking more: the tests do. Once your vet has examined the dog, it can be a complement alongside food and check-ups. The dose follows body weight. For a medium-sized dog one bottle lasts 20 to 50 days. Read more about NEPHTANNU.
Frequently asked questions
Why is my old dog drinking so much?
In older dogs, pyometra in unspayed females, Cushing's disease, diabetes, reduced kidney function and liver disease are common causes. Cortisone treatment also increases thirst. Measure over 24 hours and book an appointment. Age alone does not explain increased thirst.
How much water is too much for a dog?
More than 100 ml per kilo of body weight per day counts as too much2. For a 10 kg dog that is one litre a day.
Should I limit water if my dog urinates indoors?
No. The dog risks becoming dehydrated. Go out more often and let your vet find the cause.
Can a spayed female get pyometra?
Pyometra affects unspayed females. In a spayed female it is very rare, so your vet will mainly look among the other causes.
That was the short answer. If you have a question about your own pet, email us at info@herbiovet.se. We reply within one working day.
Read on:
Sources
- Agria Pet Insurance (Swedish), Dog drinking a lot: when should you contact a vet?
- Evidensia (Swedish), If your dog drinks and urinates a lot.
- AniCura (Swedish), Dogs that drink and urinate a lot.
- Egenvall A, Hagman R, Bonnett BN et al. (2001). Breed risk of pyometra in insured dogs in Sweden. Journal of Veterinary Internal Medicine, 15(6), 530 to 538. doi:10.1111/j.1939-1676.2001.tb01587.x
- Hagman R (2018). Pyometra in Small Animals. Veterinary Clinics of North America: Small Animal Practice, 48(4), 639 to 661. doi:10.1016/j.cvsm.2018.03.001
- Behrend EN, Kooistra HS, Nelson R et al. (2013). Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal). Journal of Veterinary Internal Medicine, 27(6), 1292 to 1304. doi:10.1111/jvim.12192