A dog loses fluid faster than she replaces it when a stomach upset brings vomiting or diarrhoea, and dehydration is the shortfall that follows. You cannot measure it precisely at home, but you can check four observable signs and watch how they change over hours. Puppies, seniors, and small dogs run short sooner than healthy adults, so the same signs carry more urgency in them. This is observation and basic husbandry only: the upset itself, its cause, and its plan belong to the vet, and encouraging drinking at home never replaces that call when the signs below say it is time.
Four signs you can check with your hands and eyes
Gums are the quickest check. Lift her lip and press a clean fingertip to the gum above a canine tooth: healthy gums feel wet and slippery, while dry or tacky gums that leave your finger sticking slightly are a dehydration clue. Skin elasticity is next: gently lift the loose skin over her shoulders into a tent, let go, and watch the return. Hydrated skin springs back at once; skin that sinks back slowly, or stays tented, points to fluid loss, although age and leanness soften this sign in older dogs. Eyes should look bright and moist; dull, dry-looking, or slightly sunken eyes support the picture. Urine completes the set, since a dog passing much less urine than usual, or none across a long stretch, is telling you output has dropped.
Encouraging drinking after an upset, with husbandry only
Offer fresh water in a clean, rinsed bowl, little and often, rather than setting down a large bowl and hoping. Refresh the water each time you offer it, since stale water interests a nauseous dog very little, and place the bowl somewhere quiet and close to where she is resting so she does not have to cross the house for it. Keep access easy through the day and evening, and let her set the pace: small, frequent drinks she keeps down serve her better than one long drink that returns. Stay calm and nearby without fussing over every lap, and note the times she drinks and roughly how the bowl level changes. Do not add anything to the water, and do not offer any rehydration product, food plan, or home remedy off your own bat; feeding and fluids after an upset are the vet's call to shape.
Watching the trend over the following hours
Recheck the gum feel and skin return every few hours and write down what you find, since a trend toward wetter gums and quicker skin return is reassuring while a trend the other way is not. Keep noting urine each time she goes out, and record continued vomiting or diarrhoea with times, because frequency is a fact the clinic will ask for directly. A dog who perks up, drinks steadily, and passes urine is moving the right way under watchful care. A dog who stays flat, stops drinking, or whose signs deepen is not a dog to keep encouraging at home.
When the vet call becomes prompt, not eventual
Phone promptly if vomiting or diarrhoea persists rather than settling, if she cannot keep water down, refuses the bowl entirely, or seems weak, wobbly, or unusually sleepy. Call the same day for a puppy, a senior, or any dog whose gums stay tacky while urine output falls. Collapse, laboured breathing, or a swollen abdomen is emergency territory at any age. On the call, report when the upset began, how often she has been sick or loose, what her gums feel like, when she last passed urine, and how much she has drunk. Her Pet Passport in KinsLe gathers those timed notes in one packet, so the advice you receive rests on facts rather than estimates.