Why is my senior dog losing weight? Weight loss in an older dog is never normal on its own — it is a sign that something has changed, and it needs a vet check, not just more food. A senior dog can lose weight for many reasons: dental pain that makes eating hurt, kidney disease, thyroid problems, diabetes, cancer, or simply the loss of muscle that comes with old age. This guide covers the causes, the warning signs, what the vet will do, and how to feed a senior dog that is losing weight. A senior dog is one from toy and small breeds from about 10 years, medium breeds from about 8 to 10 years, large breeds from about 7 to 8 years, and giant breeds from about 6 to 7 years, and from that age vet checks should move to twice a year.

The short version is: see a vet promptly if a senior dog is losing weight, especially if it is losing weight without a change in food, if it is off its food, if it is lethargic, or if it is drinking or urinating more than usual. Bring the weight record: a list of weights with dates is far more useful than a single number, because it shows how fast the weight is falling. Do not just feed more: a senior dog that is losing weight needs a vet to find the cause, and feeding more without finding it can hide the problem. The senior dog diet guide covers feeding older dogs, and the when is a dog considered a senior guide gives the senior thresholds by size.

Why do senior dogs lose weight?

Senior dogs lose weight for two broad reasons: they eat less, or they burn more than they take in. They eat less because of dental pain, because their sense of smell has dulled and food is less appealing, because they are nauseous from kidney disease or another illness, or because they are in pain from arthritis and cannot get to the bowl comfortably. They burn more than they take in because of illness: an overactive thyroid in cats, diabetes, kidney disease, and cancer all increase the body's energy use or waste nutrients, so the dog loses weight even when it is eating normally.

Muscle loss is the other cause, and it is a normal part of ageing — but it is not harmless. An older dog loses muscle every year, and a dog that loses muscle loses strength, balance, and the ability to move well. Muscle loss is slowed by good protein and by gentle, regular exercise, but it is not stopped by food alone. A senior dog that is losing weight fast, or that has lost a lot of weight in a short time, needs a vet check promptly, because fast weight loss is more likely to be illness than ageing. The arthritis in dogs guide covers the joint problems that make eating and moving hard, and the kidney disease in dogs guide covers the most common cause of weight loss in older cats.

Warning signs to watch for

See a vet promptly if a senior dog is losing weight, and the same day if it is losing weight fast, if it has stopped eating, if it is vomiting or has diarrhoea, if it is drinking or urinating much more than usual, if it is lethargic or weak, or if it has a lump, a sore that does not heal, or a change in behaviour. Those are signs that need a vet, not waiting and not more food. Bring a note of what the dog eats, how much, and any treats, and whether it has been drinking more — that information helps the vet far more than a guess about the food.

At home, watch for the small signs as well as the big ones: a dog that leaves food in the bowl, that eats slowly, that drops food, or that paws at its mouth may have dental pain. A dog that is drinking more and urinating more may have kidney disease or diabetes. A dog that is restless at night, confused, or house-training badly may have cognitive decline. A dog that is stiff, slow to get up, or reluctant to jump may have arthritis. Each of those signs is worth mentioning to the vet, because each one points to a different cause, and each one is easier to treat when it is caught early.

What the vet will do

At the vet, expect a weigh-in, a body condition score, a check of the teeth and mouth, and questions about food, water, urination, and behaviour — and usually a blood test and a urine test, because those are the usual first steps when a senior dog is losing weight, and they show whether the kidneys, the thyroid, the blood sugar, and the liver are normal. The vet may also check for lumps, listen to the heart and lungs, and feel the belly. Those checks are not overkill: weight loss in a senior dog has many possible causes, and the blood and urine tests narrow them down fast.

Depending on what the tests show, the vet may recommend a change in food, a medicine, dental treatment, or further tests. A dog with kidney disease may need a food with controlled protein and phosphorus, and more water. A dog with an overactive thyroid needs medicine. A dog with dental pain needs its teeth treated, not just softer food. A dog with diabetes needs insulin and a feeding routine. Each cause has its own treatment, which is why finding the cause matters more than feeding more. The diabetes in dogs guide and the thyroid disease in dogs guide explain the conditions that most often cause weight loss in older dogs.

Feeding a senior dog that is losing weight

Once the vet has found the cause, the feeding plan follows it. A senior dog that is losing weight because it is not eating enough needs more calories, fed little and often — two or three smaller meals a day, rather than one large meal, because a senior dog often has a small appetite. A food made for seniors, or a food with good protein to hold muscle, can help — but only with your vet's agreement, and only if the dog does not have kidney disease, where protein is controlled. Warm the food a little, or add a little water, to make it smell stronger and easier to eat — a senior dog whose sense of smell has dulled may eat more if the food smells stronger.

Feed in a quiet place, at the same times every day, and make the bowl easy to reach — a senior dog with stiff joints may struggle to reach a bowl on the floor or up a step, so a raised bowl or a bowl on the same floor as the dog's bed can help. If there are other pets in the house, feed the senior dog separately, so it is not pushed away from its bowl. Weigh monthly, and write the number down: the line over months is what matters, and a dog whose weight has steadied is a dog whose plan is working. The senior dog diet guide covers the full feeding plan for older dogs, and the how much food should a senior dog eat guide gives the calorie tables.

Muscle loss and keeping a senior dog moving

Muscle loss is a normal part of ageing, but it can be slowed: good protein in the food, and gentle, regular exercise every day. A senior dog that stops moving loses muscle fast and finds it hard to get it back, so keep the dog moving every day, at a level that suits its body — shorter, more frequent walks or play sessions rather than one long session, and play that does not strain stiff joints. Ramps or steps can help a senior dog get onto a bed or into a car without jumping, and a warm, supportive bed helps stiff joints rest.

Do not try to put weight on a senior dog with a sudden large increase in food: a dog that is fed a lot more all at once can get an upset stomach, and a senior dog with an upset stomach eats less, not more. Add about 10% at a time, wait a month, and then decide — and only with your vet's agreement, once the cause has been found. The cognitive decline in senior dogs guide covers the changes in behaviour that come with old age, and the senior dog lifespan guide explains what the senior years mean for the whole of a dog's remaining life.

For related reading, see the senior dog diet guide, the when is a dog considered a senior guide, the kidney disease in dogs guide, the diabetes in dogs guide, the thyroid disease in dogs guide, the how to weigh your dog at home guide.

Frequently asked questions

Why is my senior dog losing weight?

Weight loss in an older dog is never normal on its own. It can be caused by dental pain, kidney disease, thyroid problems, diabetes, cancer, or muscle loss with age. A senior dog can lose weight because it eats less, or because illness makes it burn more than it takes in. See a vet promptly — a senior dog that is losing weight needs a vet to find the cause, not just more food.

When is a dog considered a senior?

A dog is usually considered a senior from toy and small breeds from about 10 years, medium breeds from about 8 to 10 years, large breeds from about 7 to 8 years, and giant breeds from about 6 to 7 years. From that age, vet checks should move to twice a year, and food, weight, teeth, and kidneys should be checked each time.

What will the vet do for a senior dog losing weight?

Expect a weigh-in, a body condition score, a check of the teeth and mouth, and usually a blood test and a urine test — those show whether the kidneys, the thyroid, the blood sugar, and the liver are normal. Depending on the results, the vet may recommend a change in food, a medicine, dental treatment, or further tests.

Should I feed my senior dog more food?

Only with your vet's agreement, once the cause has been found. A senior dog that is losing weight because it is not eating enough needs more calories, fed little and often — but a senior dog that is losing weight because of illness needs the illness treated, not just more food. Add about 10% at a time, and weigh monthly.

How can I help my senior dog keep muscle?

Good protein in the food, and gentle, regular exercise every day. A senior dog that stops moving loses muscle fast and finds it hard to get it back, so keep it moving every day at a level that suits its body — shorter, more frequent walks or play sessions, and play that does not strain stiff joints.

When should a senior dog losing weight see a vet?

Promptly — and the same day if it is losing weight fast, if it has stopped eating, if it is vomiting or has diarrhoea, if it is drinking or urinating much more than usual, or if it is lethargic or weak. Bring the weight record: a list of weights with dates is far more useful than a single number.

Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.