Your dog hasn't been eating his food lately, and you don't know what to do. You're wondering how to get a dog to eat, but more importantly, how to figure out why he stopped eating in the first place. Take time to learn why your dog won't eat and how you can help.
Stress
Stressful situations and changes in your dog's environment might be the cause for his temporary refusal to eat. Has anything changed in your pet's life recently? It could be something major, like a move to a new home or starting doggy day care, or minor, like a family member leaving for a weekend trip. These changes in your pet's life might upset his eating habits. While this is certainly alarming, stressful situations and environmental changes tend to be temporary issues. If they last much longer or your dog shows other signs of stress and anxiety (like soiling in the house or destroying furniture), contact your veterinarian.
Food Change
A change in cuisine could also be to blame. Just like humans, dogs have opinions on what food they do or do not enjoy. Your pet may be simply snubbing his nose at his kibble, especially if you've recently changed flavors or brands. Don't rule out the possibility that the food you're serving your pet might have spoiled; make sure to check the expiration on the packaging. You can follow these helpful tips if your dog is a picky eater.

Illness
Loss of appetite may be a major sign that something is physically wrong with your pet. Your dog may be suffering from dental problems, making it difficult to chew and swallow. Other medical issues could range from an infection to even cancer or liver failure. If you suspect an illness as the cause of your pet's sudden decision to stop eating, make an appointment with your vet to run some tests immediately.
Look for other signs beyond not eating that might be pointing to a health related reason. For instance, if your dog has been having diarrhea or even hasn't pooped in a couple of days, he might be having some GI upset. Is he acting particularly lethargic or withdrawn? A dog that is still active and excited typically means he feels fine, so it might just be him being picky, but not eating combined with other signs can be a good indication of a health concern and you should take him to the vet to get checked.
Also, be sure to check his water intake. If he is not eating, but is drinking water he could potentially just be a picky eater. Monitor him for a day or two and see if his appetite changes. If not, and he still only continues to drink water, you should consult your vet. If he is not eating or drinking, you need to call your vet immediately. Dogs should not go a single day without drinking water.
Medication can be another potential reason your dog is eating less. While medicines and vaccinations help keep your dog healthy, sometimes an animal experiences side effects. You should monitor your dog after he is given medication and call your vet if his poor appetite lasts longer than 24 hours.