Senior Dog Not Eating: When to Wait and When to Call

How long can a senior dog go without eating?

Three to five days of too little food is where WSAVA recommends other nutritional support, so a senior dog should never wait that long at home.

The 2011 WSAVA Nutritional Assessment Guidelines recommend other nutritional support, such as a feeding tube, for hospitalized animals whose intake has been inadequate for 3 to 5 days, home days included, when adequate intake is not expected to return before nutritional status worsens. That is a hospital threshold, not a target for owners. RexVet advises a veterinary evaluation when a senior dog eats almost nothing for 24 hours, and earlier when the dog is weak, in pain or nauseated.

The table turns those anchors into a reading order. It is our triage summary of WSAVA and RexVet guidance. A dog with kidney disease, diabetes or another known illness may need your vet’s own line.

How long	What you see	What to do
Less than 24 hours	Skipped one meal, acts normal, drinks, walks and wags	Offer the usual food again in a few hours. Note the time.
24 hours or more	Eats little or nothing, otherwise bright	Call your vet today for advice or an exam.
Any length	Vomiting, collapse, weakness, labored breathing, bloated belly or refusing water	Call now. Go to an emergency clinic if the vet is closed.
Day 3 to 5	Still eating much less than usual	The dog needs a vet exam. This is the window where WSAVA recommends other nutritional support.
Weeks	Eats a little but weight and muscle are dropping	Book an exam. Slow loss is still a medical finding. See senior dog losing weight but still eating.

The “any length” row follows common veterinary advice on warning signs. A dog with those signs should not be left to see whether it eats tomorrow.

Senior dog not eating but drinking water: should I worry?

A senior dog that drinks but does not eat needs a vet call if it misses more than a day of meals.

Drinking tells you the dog is taking in some fluid. It does not tell you why the dog is not eating. Merck Veterinary Manual lists loss of appetite alongside weight loss, vomiting, dehydration, mouth sores and diarrhea as signs of advanced kidney disease. It says kidney disease becomes more common from age 5 to 6 and affects up to 10% of elderly dogs. Dental pain, nausea and other causes covered below also leave thirst intact.

If your dog drinks far more than usual or has accidents, tell the vet. That pattern calls for its own tests, and our guide to a senior dog drinking a lot of water explains why.

Is my old dog eating enough? A calorie check

If your dog’s usual intake matches the reference below, eating half a meal supplies about 68% of its resting energy needs.

Resting energy requirement (RER) is the energy a dog uses lying quietly. A Canadian Veterinary Medical Association nutrition proceeding gives the formula as 70 x (body weight in kg) to the power 0.75. WSAVA says vets may use this kind of formula for hospital patients. A 2025 feeding trial used 95 x kg^0.75 as the energy need of an inactive adult dog. We use that as the reference for a usual day.

Here is the arithmetic for two dogs. Both numbers are population estimates.

	10 kg (22 lb) dog	30 kg (66 lb) dog
kg to the power 0.75	5.62	12.82
RER (70 x that)	394 kcal	897 kcal
Inactive adult reference (95 x that)	534 kcal	1,218 kcal
Eats 75% of the reference	401 kcal (102% of RER)	913 kcal (102% of RER)
Eats 50% of the reference	267 kcal (68% of RER)	609 kcal (68% of RER)
Eats 25% of the reference	134 kcal (34% of RER)	304 kcal (34% of RER)

For a dog that normally eats the reference amount, three quarters of a meal is near resting needs, half is about two thirds of them and a quarter is about one third.

To use this, read the calories per cup or per can on your dog’s food label. Say a food lists 350 kcal per cup and a 10 kg dog eats three quarters of a cup. It takes in about 262 kcal, roughly 67% of the 394 kcal RER. Your own label gives your own numbers.

WSAVA says energy needs can vary by 30% in either direction for dogs, and an old dog that moves less may need less than the reference, so treat the table as a starting point. Your vet sets the calorie target.

Muscle matters too. WSAVA notes that sick animals lose more muscle than healthy animals deprived of food, who lose mainly fat. Feel along the spine and hips each week and weigh your dog on the same scale. A drop in weight or a bony spine is a reason to book an exam even if the dog is still eating something.

Why is my old dog not eating? Causes vets check first

Possible causes include mouth pain, kidney disease, nausea and pain elsewhere, and a vet exam is how they are told apart.

• Dental and mouth pain. Merck Veterinary Manual calls gum disease the most common oral problem in small animals and says loss of appetite may be seen. Pawing at the mouth and resisting handling are signs of pain. A dog may want food and be unable to chew it.
• Kidney disease. Merck says kidney disease affects up to 10% of elderly dogs. Later stages bring vomiting, weight loss, mouth sores and loss of appetite. Merck advises dogs with kidney disease to see a vet every 3 to 6 months.
• Nausea and vomiting. The 2025 mirtazapine study notes that controlling pain and nausea is part of restoring intake in sick dogs. Medications can also upset the stomach. RexVet lists medication side effects among its causes. Tell your vet about every drug and supplement.
• Pain elsewhere. Sore joints can make a dog reluctant to stand at a bowl. If your dog also slips or struggles to rise, see back legs giving out in an old dog.
• Cognitive change. In the Dog Aging Project study of 15,019 dogs, 1.4% scored as having canine cognitive dysfunction, and the odds rose 52% with each added year of age. Its rating scale asks how often a dog has trouble finding food dropped on the floor. The authors warn that poor sight or hearing can produce the same answers. A dog that wanders past its bowl may have a sensory problem, a cognitive one or both. Our dog dementia signs checklist goes through the other behaviors to watch.

Use the list as questions to put to your vet, since only an exam separates these causes.

What to feed a senior dog that won’t eat

Offer the dog’s usual and favorite foods first, since WSAVA warns that new foods can teach a dog to dislike them.

The WSAVA guidelines give these steps for animals with low appetite:

• Offer usual and favorite “comfort” foods. Avoid new foods meant for long-term feeding, because a dog can link a food with feeling sick and then refuse it.
• Warm the food, move the dog to a quiet spot, feed by hand or stroke the dog while it eats.
• Be careful with syringe feeding in dogs with nausea or stress, because it can cause food aversion.

If those steps fail, the cause needs treatment. In the mirtazapine study (107 case records and a 25-dog crossover trial) treated dogs were more likely to eat again (odds ratio 3.06) and food acceptance on day 1 was 100% against 63.6% on placebo. No significant difference was detected on day 2, and the authors point to carryover and concurrent clinical improvement as limits on interpretation. They call the drug a short-term, second-line option when feeding tubes are not possible. It is a prescription medicine, so your vet chooses the dose.

What to tell the vet when you call

Write down what your dog ate, when it last ate and what else changed, because the vet will ask for exactly that.

WSAVA lists the history a vet collects on appetite: changes in the amount eaten, chewing, swallowing, nausea, vomiting and regurgitation. Have these ready:

1. The date and time of the last full meal and the last snack.
2. How much your dog eats on a normal day (cups or cans) and how much it ate today.
3. Whether it drinks, and whether it drinks more or less than usual.
4. Any vomiting, diarrhea, black stool, coughing, panting or accidents.
5. The last weight, if you have one, and a photo of the ribs and spine from above.
6. Every medicine and supplement, with start dates.
7. Any chewing on one side, dropping food, drooling or pawing at the mouth.

Film anything odd, such as a dog that turns away at the bowl. Video helps when the dog behaves normally in the clinic.

Do dogs stop eating before they die?

Loss of appetite can happen near the end of life, but it also comes with many treatable illnesses, so only a vet exam tells which applies.

Appetite loss on its own is not a sign of dying, and this page gives no timeline for it. If your dog is old, has a known serious illness and has stopped eating, ask the vet what to expect and what would keep your dog comfortable. Our guides to the signs an elderly dog is dying and how to know when to put your dog down cover that stage, and more older-dog topics are in our senior dog guides.