Cat & Dog Water Intake: Daily Amounts and Changes

A cat needs about 50 mL of water per kg of lean body weight each day in total, and much of that can come from food. Cornell’s figure works out at about one cup a day for a 10-pound (4.5 kg) cat. An overweight cat’s estimate is lower than its scale weight suggests.

That is not the amount a cat has to drink from a bowl. Cornell says cats on wet food, which can be up to 80% water, may drink less, while cats on dry food usually take more of their water by drinking. Merck notes that cats often do not drink a lot of water, and PDSA says it is quite common to see a cat drinking only now and again. So a quiet water bowl is not a problem in itself. A change from what your cat usually does is more telling.

Sometimes the reason is ordinary, such as heat, exercise or a change of food. If there is no clear reason, or the increase continues, speak to your veterinarian.

What it can look like

• Filling the bowl more often, or finding it empty sooner
• Drinking from taps, puddles, the bath or the toilet
• Passing urine more often or in larger amounts, or more litter tray visits
• Accidents indoors, or more stops on walks

Ordinary reasons

PDSA lists hot weather, more exercise and a change of diet among short-term reasons in dogs, particularly a saltier or drier food. Moving from wet food to dry means a pet needs to drink more to make up the difference. A change of bowl, room or routine is also worth noting, because it can affect how you read what you see.

Reasons a veterinarian may look into

PDSA and Cornell list many possible medical causes. In dogs these include urinary problems, diabetes, kidney disease, Cushing’s disease, liver disease and a womb infection called pyometra. In cats, PDSA lists urine infection, kidney disease, diabetes, hyperthyroidism and fever. Some medications, such as steroids, also increase thirst. Thirst alone cannot tell you whether any of these applies. That takes an examination and usually tests.

PDSA suggests telling your vet how much your pet drinks in 24 hours. This method measures bowl water only, and it is an approximation. Using the same method each time is what makes the numbers comparable.

1. Pick a start time. Measure at the same time each day, using the same bowls.
2. Measure what you put in. Use a measuring jug, or weigh the water on kitchen scales, since 1 g of water is about 1 mL.
3. Write down every top-up. Measure each refill and add it to the total.
4. Measure what is left after 24 hours. Water added minus water left is your day’s figure.
5. Allow for evaporation and spills. A second bowl of water placed where pets cannot reach it shows how much evaporates. Note any spills, because you cannot measure them.
6. Count every water source. Include fountains and extra bowls, and note any drinking you know happened elsewhere.
7. Be honest about shared bowls. A shared bowl gives you a household total, and dividing it does not give an individual figure. If you need one animal’s number, ask your veterinarian how to arrange it. Never remove water from the others to get it.
8. Record wet food separately. Note the type and amount of food, and keep it out of the bowl figure.
9. Compare several days. One unusual day says little. Record the weather, exercise and food alongside. If you are worried, call your vet without waiting to finish.

Worked example

You put out 500 mL and top up with 300 mL, so you added 800 mL. After 24 hours, 220 mL is left, and your unreachable bowl lost 20 mL. That gives 800 − 220 − 20 = about 560 mL drunk. Compare that with your pet’s other days more than with a chart.

Note urination too, because Merck’s guidance for dogs and for cats shows veterinarians ask about both: how much your pet drinks, how often it urinates, how much, how the urine looks and how it behaves. For cats, the number and size of litter clumps is a useful rough observation, though it is not a measurement.

Contact your veterinarian if your pet is drinking noticeably more or less than usual and you cannot explain it. You do not need to finish measuring first. It matters more when a change in thirst comes with any of these:

• Passing much more urine, accidents indoors, or straining to urinate
• Eating less, or losing weight
• Low energy, weakness or a sudden change in behaviour
• Vomiting or diarrhoea, or drinking so much that your pet vomits
• Dry or sticky gums, or sunken eyes

The Merck Veterinary Manual places failure to eat or drink for 24 hours among signs needing immediate attention, alongside difficulty breathing, seizures, straining but failing to urinate or defecate, severe or constant pain, and extreme lethargy. Excessive water consumption sits in its within-24-hours group, with vomiting or diarrhoea for more than 24 hours, a sudden change in behaviour, and sudden weight gain or loss. Neither list is exhaustive.

A single day’s water figure says little, but a run of them alongside everything else says more. Patter records and analyses the water intake you enter, in the same profile as your pet’s food, calories, weight, mood, daily checks and vet visits, so a change in drinking can be read against what else changed. See nutrition in Patter and health in Patter, for cats and dogs.

Patter can surface a change worth a closer look and recommend veterinary follow-up. It works from what you record, and it does not diagnose dehydration or any other condition. Patter and your veterinarian explains where that line sits.