If your dog suddenly starts eating less than her well-established norm, it's reason enough for a trip to the vet's office. Minor appetite fluctuations occur sometimes and are perfectly natural, and external factors like different food, increased treat feeding and changes in activity level can affect how much your pet eats. However, a number of illnesses, from the fairly benign to the very serious, can cause a noticeable and lasting decrease in appetite.
You have good reasons to be concerned about your dog eating less than normal. Most importantly, it may point to an underlying illness that needs veterinary attention. It can also lead to weight loss, vitamin or mineral deficiencies, anemia, stunted growth in puppies, problems with offspring in pregnant dogs or other effects of malnutrition. Your dog might also lack the energy necessary to get enough exercise or go about other aspects of her daily routine.
Stress is often implicated in a dog's loss of appetite. Consider whether your dog is dealing with significant environmental changes or alterations to her familiar routine or schedule. The addition of a new pet or human family member, or the loss of either, can be quite stressful for a canine, too. If there's construction on your street, lots of thunderstorms lately or other sources of loud or continuous noise, it can have a considerable adverse effect on your dog's mental state and desire to eat. Work to eliminate sources of stress or consult your vet about acclimating your dog to unavoidable changes and other management strategies.
Infections and Other Illnesses
Countless types of infections and diseases can trigger a decreased appetite in dogs. Parasitic intestinal worms, GI infections, inflammatory bowel syndrome or diseases, periodontal disease, liver and kidney failure, cardiac disease and various cancers are all common culprits. But just about any illness can make your dog less hungry or prompt her to eat less due to related discomfort or pain. Aging can, too. If your dog is taking a new medication or supplement, loss of appetite may be a side effect; check the label. Your vet will consider the history, accompanying symptoms and results of a physical examination to determine which tests to run and to arrive at a diagnosis.
Obviously, the appropriate treatment for your dog's loss of appetite depends largely on the cause. Talk to everyone else in your home to make sure nobody's feeding your dog meals or treats you're unaware of. If your vet gives the OK, increase your dog's physical activity a bit to stimulate her appetite. If your pet takes a new drug or supplement, discuss the side effect with your vet and discuss management or alternative therapies. Follow all your vet's instructions for treating any infection or other illness diagnosed as the cause of your dog's decreased appetite.