Feeding Table Scraps
If you or someone in the household is feeding your dog table scraps or other treats, this can cause your dog not to eat her own food. In fact, this is one of the main causes of lack of appetite in dogs.
New Food
Another common cause of picky eating in dogs is new food. Even though you may think the new food you bought for her may smell delicious, she may not like it. Sometimes it is better not to change food unless your veterinarian suggests it because of an allergy.
Digestive Upset
Just like a human, if her stomach hurts, she is not going to want to eat anything. If this does not pass within 24 hours, you should call your veterinary care provider.
Side Effect of Medication
Some medications can make your dog feel nauseous or have an upset stomach. If you have started your dog on any kind of new medication or supplement recently you should call your veterinarian for advice. Also, never give your dog medication or supplements without talking to the veterinarian first.
Anxiety or Depression
Another commonality with humans, some dogs do not have much of an appetite when they are anxious or feeling depressed. If there has been a change in the household such as a recent move or loss (or gain) of a household member, this can cause a temporary lack of appetite. Call the veterinarian if it lasts longer than one day.
Pain
If your dog has any kind of pain, this can cause your dog to lose her appetite, especially if she has some sort of dental pain like a bad tooth or gum disease. Call your veterinarian if she refuses to eat for longer than one day.
Poisoning
If your dog has ingested some type of toxic material such as a poisonous plant or cleaning substance, they will not want to eat anything. There should be other symptoms with this kind of issue such as vomiting or diarrhea.
Cancer
Many types of cancer can cause anorexia (loss of appetite) in dogs. Other symptoms to watch for are weight loss and extreme lethargy.
Hormonal Disorder
Some hormonal disorders can cause an imbalance or overabundance of certain chemicals, called metabolic disease. This imbalance in the blood may cause lack of appetite or picky eating. Other symptoms you may notice include increased or decreased sleeping, frequent urination, and weight loss or gain.