Start by measuring, not eyeballing the bowl
A dog is drinking too much when his intake is clearly and persistently above his own normal, and the only reliable way to know is to measure it. Fill the bowl from a measuring jug, record the amount, note every top-up, and measure what is left in the morning for at least three ordinary days. Compare those figures with what you know of your dog's habits in the same season and routine. One huge drink after a hot run or a salty treat is normal physiology, not a warning sign. A bowl that suddenly needs refilling twice as often, every day, is a pattern worth taking seriously.
Normal reasons a dog drinks more
Plenty of innocent explanations raise a dog's thirst for a day or two, and ruling them out sharpens what you report to a vet. Warm weather, longer or harder exercise, dry heated indoor air, and a switch to a drier food all legitimately increase drinking. A dog who has been swimming, playing hard with other dogs, or eating something salty will tank up heavily and then settle. Nursing mothers also drink far more than usual, which is expected. The key question is whether intake settles back to your dog's baseline once the cause passes. Drinking that stays high with no matching explanation is the change that matters.
The companion signs that make thirst meaningful
Excess drinking rarely travels alone, and its companions point the conversation with your vet. Watch for larger puddles or more frequent urination, a dog who asks to go out at night when he never did, or new accidents in a reliably house-trained dog. Note appetite changes in either direction, weight drifting up or down, and energy that seems flatter than usual. Check whether your dog hovers at the bowl, seeks water in unusual places like dripping taps, or wakes to drink during the night. Written down with dates, these observations turn a vague worry into a clear, useful history.
What increased thirst can be connected to
Vets take a sustained rise in drinking seriously because it can accompany several body systems working harder than they should, including the kidneys, the organs that manage blood sugar and hormones, and the liver. It can also follow a urinary infection making a dog drink and urinate more, or appear as a side effect after certain prescribed treatments, which is why your vet will ask what your dog currently receives. None of this can be sorted out from the kitchen floor: distinguishing among these possibilities takes an examination and usually simple blood and urine testing. Your measured log is the piece only you can supply, and it genuinely shapes that first appointment.
When to call the vet about drinking
Call promptly when the higher intake has lasted several days with no weather, food, or exercise explanation, or when it arrives with night-time urination, accidents, appetite change, or unusual tiredness. Call the same day if your dog drinks frantically yet seems unwell, vomits, stops eating, or appears weak or disoriented. Puppies, seniors, and dogs with known long-term conditions deserve a lower threshold, since their reserves are smaller. Never restrict water while you wait to be seen; a thirsty dog needs access, and limiting it can do harm. Bring your numbers, because 'about double for five days' gets a faster, better response than 'quite a lot lately.' Storing that log in your dog's KinsLe Pet Passport keeps his intake history packed with the rest of his records, ready for the vet visit.