How long a missed meal can wait depends on the dog
A healthy adult dog who skips one meal but drinks normally, stays bright, and happily takes a favorite treat can usually be watched closely at home for the rest of that day. Refusal of all food, including high-value treats, for a full day is the point to call the vet rather than keep waiting. A dog who is not eating and also not drinking, or who cannot keep water down, needs to be seen urgently regardless of age or size.
The company the appetite loss keeps
Not eating alone is vague; what comes with it points the vet in a direction. Vomiting, diarrhea, drooling, repeated lip licking, or a hunched posture alongside food refusal suggests nausea or abdominal discomfort. Excessive thirst with appetite loss, weight loss over recent weeks, bad breath with drooling and dropping food, pawing at the mouth, bleeding gums, or a broken tooth each suggests a different area to examine. Lethargy, hiding, whimpering when picked up, a swollen belly, collapse, or difficulty breathing turn missed meals into an emergency presentation.
What to observe and write down at home
Note exactly what was offered and refused, including whether your dog approaches the bowl and walks away, sniffs and licks but does not chew, or shows no interest at all. Record water intake as best you can, toilet habits, any vomiting or stool changes, and whether energy, tail carriage, and interest in walks look normal. Check the mouth only if your dog tolerates it calmly, looking for a lodged stick across the palate, red gums, or a foul smell, and stop if your dog resists. Avoid force-feeding, syringe feeding, or cooking increasingly rich tempting foods for days on end, because that can worsen nausea and delays the examination that would identify the cause.
When stress or pickiness is the likelier story
Some dogs stop eating for situational reasons: a house move, visitors, a new pet, fireworks, a changed feeding spot, or a sudden switch to a different food. In those cases the dog usually remains bright, drinks well, toilets normally, and will accept something familiar within a meal or two. Even then, keep the window short. If the situational explanation does not resolve quickly, or you find yourself explaining away new signs to fit it, book the visit.
What the vet will want to know on arrival
Expect questions about duration, exact foods offered, water intake, vomiting and stool, recent diet changes, access to trash or toxins, travel, other pets, and all medications and supplements. A physical examination may include temperature, hydration, abdominal feel, mouth and teeth, and listening to chest and gut sounds, with blood work or imaging suggested if the cause is not obvious. Your written notes save time here and improve accuracy, because owners reliably forget day-by-day details by the time they are in the consulting room, especially when they have been worried and sleeping poorly. Bring previous appetite or weight notes too if this has happened before.
Turning one episode into a useful pattern
A single hungry strike is an incident; a recorded pattern of them is clinical information. Note the date appetite dropped, how long it lasted, what else was happening, what the vet found, and how quickly normal eating returned. If episodes repeat around stress, diet changes, or a particular season, that pattern becomes visible on paper in a way memory blurs. KinsLe's Pet Passport keeps meal-refusal notes, weights, and vet findings together for a dog whose appetite dips, so a repeat episode can be compared honestly with the last one.