Sudden weight loss in a dog that is not attributable to increased exercise or activity should be brought to the attention of your veterinarian. Some dogs do experience cyclical weight changes because they live in seasonal climates and are exercised and walked less during the cold winter months.
To be healthy, a dog should have sufficient fat covering the ribs. If your dog’s ribs start showing where they did not before, it could be an indication of a serious problem with your pet.
Hyperthyroidism, a disease of the thyroid gland, can cause sudden weight loss if a dog’s system contains excess amounts of the thyroid hormone, putting a dog’s thyroid on overdrive and causing the dog to become sluggish.
There are other diseases that can cause sudden weight loss in dogs such as Addison’s Disease, which is a deficiency of the hormones in the adrenal glands. Some of the signs of Addison’s include severe dehydration when plenty of water is always available to the dog, and a rapid loss of appetite followed by sudden weight loss.
Sudden weight loss can also be a result of inflammatory bowel disease which occurs when a dog’s stomach or intestines react adversely to inflammatory cells like lymphocytes. A dog with inflammatory bowel disease usually will display signs of weight loss, a loss of appetite, lethargy, and diarrhea. Gastritis displays the same symptoms and is caused when a dog gets an infection or inflammation in the stomach area. If a dog eats spoiled food, its stomach lining can become irritated and the result is a change in its appetite. Diabetes will also display the same symptoms.
Parasite-borne diseases can also cause a sudden weight loss in dogs and these are caused by hookworms, roundworms, heartworm disease, giardiasis, mange, or salmon poisoning disease, a bacterial disease contracted by eating salmon or trout that carry the parasitic organisms.
The signs and symptoms of many types of tumors, including pituitary, stomach, pancreas, colon, lungs, or kidneys can also result in a sudden weight loss in dogs. Fungal infections such as histoplasmosis, blastomycosis, or aspergillosis will also cause a sudden weight loss.
Weight loss in a dog is not a life-threatening emergency, but your pet will still need veterinary care. You should schedule an appointment for a complete diagnosis to determine the underlying cause.