What this means
A dog who is losing weight can be spotted by more than the scales. The ribs, spine or hip bones become prominent, the muscle around them seems to waste, and the coat may dull. Compare your dog with older photos and write down when the thinning began and how fast it has gone.
It helps to note how your dog eats. Some dogs eat more than usual and still get thinner, which is an important clue. Others eat half-heartedly or refuse altogether. Also look at the stools, vomiting, thirst and urination, because several different illnesses show themselves through exactly these changes alongside the thinning.
Older dogs can get thinner through changes that come with age, but even then the cause is worth checking, because behind it there is often something a vet can identify. Weight loss is sometimes caused by pain in the mouth or elsewhere that makes a dog avoid eating, so an examination looks at the whole dog.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
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A shortage of pancreatic enzymes
The pancreas does not make enough enzymes to digest food, so the dog absorbs less than it eats. The dog is constantly hungry but thin, and the stools are bulky, greasy and pale.
About the condition: Exocrine pancreatic insufficiency (EPI) -
Diabetes mellitus
The dog cannot use sugar properly, so loses weight despite eating a lot. A big thirst and frequent urination go with it.
About the condition: Diabetes mellitus -
Kidney disease
Weakened kidneys lower the appetite and cause nausea, so the dog gets thinner. Increased thirst and lethargy are often noticed.
About the condition: Kidney disease -
Tumours
A tumour draws on the body's energy and can upset the appetite. Weight loss is one of the earlier and quieter signs.
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Long-term bowel disease
An inflamed bowel absorbs nutrients poorly, so the dog thins although it eats. Recurring diarrhoea or vomiting is typical.
About the condition: Inflammatory bowel disease (IBD) -
Difficulty eating because of mouth pain
Painful teeth or gums make a dog eat less or avoid harder food. Drooling, a bad smell from the mouth or dropping food from the mouth can be seen.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- When your dog began to thin and how fast
- Whether your dog eats more, less or the same as usual
- Whether the stools are changed, bulky or greasy
- Whether your dog drinks and urinates more than usual
- Whether there is vomiting or nausea
- Whether your dog avoids harder food or drools
When to book a routine visit
Book a visit if your dog is thinning for no clear reason, even if eating well, or if the weight loss comes with a change in thirst, stools or appetite. If your dog stops eating, is very weak or is vomiting, go straight away.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Exocrine pancreatic insufficiency (EPI) Digestion and liver This is a condition in which the pancreas doesn't produce enough digestive enzymes, so food passes through almost undigested and the body misses out on the nutrients it needs. As a result, a dog can eat for two and still lose weight. A vet confirms whether it really is EPI with tests.
- Diabetes mellitus Hormones and metabolism Diabetes mellitus is a disease in which the body makes too little insulin or can no longer use it properly, so sugar cannot move from the blood into the cells and builds up in the bloodstream. The body's cells go short of energy even though the dog is eating enough, and blood sugar that stays high for a long time can harm various organs, such as the eyes. It is a long-term condition that needs ongoing monitoring together with a vet.
- Kidney disease Kidneys and bladder The kidneys filter the blood, remove waste from the body and help keep the balance of fluids and salts. When they are damaged suddenly, for example by poisoning or infection, or weaken gradually over a longer time, substances they should remove start to build up in the body. Long-term kidney changes can go unnoticed for a long time, because the healthy part of the kidneys takes over the work for a while.
- Cancer Cancer Cancer is not one disease but a whole group of different malignant tumours that can appear in almost any organ or tissue. They can grow slowly or quickly and spread to other parts of the body, so the earlier a change is noticed, the more options a vet has. Only a vet can tell whether a lump or other change is malignant.
- Inflammatory bowel disease (IBD) Digestion and liver This is a long-term disorder of the digestive tract in which inflammatory cells build up in the wall of the stomach or intestine, so it becomes less able to digest food and absorb nutrients. The exact cause is not fully understood; an interplay between the immune system, gut bacteria and food is thought to play a part. Because many other digestive problems look much the same, a vet works out what is really going on with tests.
- Giardiasis Parasites Giardiasis is a gut disease caused by single-celled parasites called Giardia. A dog becomes infected by swallowing their cysts with water, grass or another dog's faeces. The parasites disturb the absorption of food, so the stools turn soft and the diarrhoea keeps coming back; a vet identifies the parasites from a stool sample.
- Intestinal worms Parasites Intestinal worms are parasites that live in a dog's gut: roundworms, tapeworms, hookworms and whipworms. Any dog can become infected, and puppies even before birth or through their mother's milk. Some dog worms are dangerous to people too, especially children; which worms a dog has is for a vet to establish from a stool sample.
Body systems: Digestion and liver Hormones and metabolism Kidneys and bladder Cancer Parasites