There are many causes of rapid weight loss in dogs. It can be caused by medical problems. Disease of the liver, pancreas, and intestines can cause the food not to be absorbed properly. Vomiting and dog diarrhea may be present. Dog weight loss accompanied by increased water intake and urination may indicate kidney disease or diabetes. Heart disease can cause weight loss in which the body does not get the proper nutrition because of poor circulation. Dog worms or other canine parasites can steal your dog’s nutrition.
If your dog is just a little underweight, there may not be anything seriously wrong. Toy breeds are sometimes picky about their food. Adding a teaspoon of canned dog food to the dry food may tempt it to eat better. Some dogs prefer their food be soft and moist.
Healthy pets that are lean usually have less joint, heart, lung and pancreatic problems.
Dogs that are underweight are not receiving enough calories. If your dog is burning up more calories than it is taking in or eating a food that in not digestible, it may be losing weight. Some dogs are hyper and you may have to cut back on the amount of exercise he gets.
If your dog does not seem ill and is active and alert, you can start by increasing it’s caloric intake. You may need to increase the protein and fat contents in your dogs food. Vitamins may increase your dogs appetite too.
If no weight gain is seen with increased food intake or if the weight loss is accompanied by signs of illness in the dog, you should see your vet.
Your vet may want to do a blood test, stool sample, urinalysis, electrocardiogram, ultrasound, endoscopy, and x-rays to find the underlying cause for the canine weight loss.