Is my dog drinking too much water? How to measure at home

Let me guess. You're filling the water bowl more often than your own coffee cup, and your dog has decided the toilet is a perfectly good backup. Maybe he's started asking to go out at 2 a.m. Maybe there's been an accident in the house from a dog who hasn't had one in years. And now you're wondering if your dog is drinking too much water, or if you're imagining it.

Take a breath. Let's walk through it the way I would if you were sitting across from me.

This usually isn't a middle-of-the-night emergency

If your dog is drinking more but otherwise acting like himself, this is a "call your vet and book a visit" problem, not a "rush to the ER tonight" problem. There are a couple of exceptions, and I'll get to them at the end.

While you wait for that visit, you can do the single most useful thing an owner can do for me: get me a number.

How much water should a dog drink a day?

Most healthy dogs drink somewhere around half an ounce to an ounce of water per pound of body weight a day. For a 20-pound dog, that's roughly 1½ to 2¼ cups. For a 50-pound dog, roughly 4 to 5¾ cups.

That's a guide, not a rule. Dogs drink more on hot days and after a long walk. Dogs on canned food drink less from the bowl, because canned food is mostly water. And your dog's own normal matters more than any chart. A lifelong big drinker is a different story from a dog whose drinking has clearly changed.

When is a dog drinking too much water?

The line I use is about 1½ ounces per pound a day. Here's the quick math for your dog: his weight in pounds times 1½ is roughly the line in ounces. Divide by 8 to get cups.

• For a 20-pound dog, that's a little under 4 cups a day.
• For a 50-pound dog, it's about 9½ cups. Well over half a gallon.

Between normal and that line is a gray zone, and that's where a change from your dog's usual matters most.

The jug method

Most of us have no idea how much our dog drinks. We just know we keep filling the bowl. So let's measure it. It takes about two minutes a day.

1. Pick a jug. A big measuring pitcher is perfect. A clean gallon jug and a measuring cup work too.
2. Fill it in the morning and write down how much is in it.
3. For the next 24 hours, fill the bowl only from that jug. Pick up any other bowls. Put the toilet lid down. (He'll be disappointed. He'll get over it.)
4. Next morning, same time, measure what's left in the jug and the bowl, and subtract it from what you started with. That's what he drank, give or take a little splashing.
5. Write the number down with the date, or log it in WagNote's water tracker.

Why a full 24 hours? Because a few hours can fool you. Morning to morning catches the afternoon gulps and the 2 a.m. trips to the bowl. If you can, do it two or three days in a row, and jot down if it was hot or he had a big walk. If two pets share the bowl, the number is for the household. That's still useful. Just tell your vet.

"She's drinking about 9 cups a day" beats "I think she's drinking more" every single time. Honestly, that's why I built WagNote (full disclosure: it's my app). I kept seeing owners struggle to keep track of numbers like this, so I put it all in one place.

Don't take the water away

I know it's tempting, especially when you're mopping up accidents. Don't. In most of these dogs, the body is losing extra water in the urine first, and the thirst is your dog trying to keep up. He isn't peeing more because he's drinking more. He's drinking more because he's peeing more. Take the bowl away and the peeing doesn't stop. He just gets dehydrated.

What helps is more trips outside. Fewer accidents, happier dog.

Why is my dog drinking so much water?

The list is long. The ones I think about first:

• Kidney disease. Tired kidneys can't concentrate urine, so more water goes out and your dog drinks to replace it. It's common in older dogs, so it's high on my list when a senior dog starts drinking a lot of water.
• Diabetes. High blood sugar spills into the urine and drags water out with it. The classic picture is a dog who's eating more and still losing weight.
• Cushing's disease. Too much cortisol, the body's stress hormone. These dogs are often always hungry and panting, with a pot belly. I wrote more about it in what I tell owners about Cushing's.
• A bladder infection.
• Pyometra, a womb infection in a female who isn't spayed. More on this one below, because it can't wait.
• Medicines. Prednisone and other steroids, phenobarbital for seizures, and water pills can all make dogs thirsty.
• Less common ones, like liver disease, Addison's disease, some cancers and leptospirosis.

You can't tell these apart at home, and I can't tell them apart by looking at your dog either. Thirst alone doesn't point to one cause.

What happens at the vet

When a dog comes in drinking too much, I start with a urine test and bloodwork. To me, that's the essential starting point. The urine tells me how concentrated it is and whether there's sugar or infection. The bloodwork checks the kidneys, the liver and the blood sugar. Depending on what turns up, the next step might be more bloodwork, x-rays or an ultrasound.

If you can bring a urine sample, a morning sample is best. Bring it in the same day. If you can't get it in right away, put it in the refrigerator, and label it clearly so nobody in your house gets a surprise. Every vet's a little different, so when you book, ask whether yours wants a sample and how they'd like it collected.

And bring your water numbers. They give your vet a real starting point, and later on they're one of the easiest ways to see if treatment is working.

When it can't wait

Two exceptions to "book a visit":

An unspayed female who's drinking more. Call your vet today. Pyometra often shows up a month or two after a heat, and it's an emergency. The good news: it usually goes well when it's caught early.

A dog who's drinking a lot and also seems sick. If he collapses, is very weak, keeps vomiting, has trouble breathing or can't pee, go now. Same if there's any chance he got into antifreeze.

If you do one thing this week: do the jug method for one full day and write the number down with the date, or log it in WagNote. Your vet will love you for it.