Based on my experience, I agree that most of the time temporary loss of appetite is not an emergency.
There are many physiological as well as psychological reasons a dog can lose interest in food.
The reasons might be well-known, such as with Jasmine's IBD, or any chronic disease. It can be because the dog's stomach is upset from a prior adventure in the garbage can or otherwise getting their paws on something they should not have eaten. Stress and anxiety can make a dog lose interest in food. Pain can make a dog not want to eat. If a dog feels unwell for any reason it can result in loss of appetite.
Some dogs have the tendency to be finicky eaters, though my personal belief is that there also ought to be a reason for that. Of course, access to food stuffs better than what appears in the bowl might be one of them.
I do recommend, that as with any change of behavior or habits, loss of appetite warrants a vet visit.
Does that make it an emergency, though? There are times when it can.
This is when being observant and knowing your dog is so important.
In my interview with veterinarians about what symptoms should be taken seriously, Dr. Buzby shared a story of close friend's dog who could have lived if somebody understood the significance of her not being interested in food. Dr. Buzby emphasizes that in most dogs, such change is a major red flag.
The dog lost her life because of a major bleed from a massive spleen tumor. Before her final tragedy, she wasn't eating normally for weeks.
It was not an emergency at the time it started but it did turn into one.
Coincidentally, a friend of mine was consulting with me about home remedies for a dog with an upset stomach. Not eating well. So it happens that this dog's digestive problems and disinterest in food were also rooted in a mass on the spleen and the liver.
Loss of appetite CAN be a sign of an emergency.
It can be an emergency when your dog is on certain medications or could have gotten into something toxic. It can signal liver or kidney failure. It can be the only observed sign of high fever. Complete loss of appetite can be a sign of an impending diabetic emergency.
On top of that, not eating alone begins to become a problem in itself, particularly with puppies or small dogs.
Do I rush my dog to the emergency every time they don't eat?
No, of course not. But when Jasmine stopped eating and drinking while being on NSAIDs, have I not take action, she might have suffered serious damage.
When Cookie was lethargic and not eating, have I not taken action, I would have missed having her pancreatitis diagnosed and treated early.
Unlike with some of the other symptoms, there isn't a solid cover-all rule when it comes to loss of appetite.
Don't even ignore such change and use your best judgment in determining how quickly your dog should see a veterinarian.
Symptoms to Watch for in Your Dog: Loss of Appetite
Dog Medical Emergencies Survey
Dog Medical Emergencies Survey Results
Is Unproductive Retching an Emergency?
Is Difficulty Breathing an Emergency?
Is Panting an Emergency?
Is Severe Pain an Emergency?
Is Limping an Emergency?
Is Vomiting Bile in the Morning an Emergency?
Is Profuse Vomiting an Emergency?
Are Convulsions or Seizures an Emergency?