Causes
A loss of appetite in cats is called inappetence. While your cat might not like the food you're offering, a lack of appetite is often a symptom of an underlying issue. Cats may stop eating if there's something stuck in their stomach or intestines or if they aren't feeling well because of an underlying disease or infection.
Your cat's lack of eating can also be a sign of pain or discomfort. Even stress can affect a cat's appetite. Regardless of the cause, it's a significant concern if your cat stops eating.
Common causes of inappetence are:
Psychological
• Dislike of new food.
• Moving to a new home.
• New pet or baby joining the family.
• Travel to unfamiliar location.
• Other stress (e.g. bullied by another pet, hospitalization).
Medical
• Kidney infection or chronic kidney disease.
• Vaccination side effect.
• Parasites.
• Dental issue (e.g. toothache).
• Oral ulcers.
• Digestive system disease (e.g. stomach, esophagus, liver).
• Allergies.
• Cancer.
• Liver disease.
• Infections.
• Trauma/injury.
• Ingestion of poison.
Symptoms
Although the clearest sign that your cat is not eating is to observe them refusing food each time it's given to them, there are other symptoms that can be present that can help narrow down what may be causing the food avoidance.
Keep a lookout for any of the following signs, as they can indicate an underlying disease:
• Lethargy
• Excessive drooling
• Dehydration
• Vomiting
• Diarrhea
• Weight loss
• Change in behavior
• Labored breathing
• Signs of infection (e.g. pus discharge)
• Bad breath
• Red gums
• Bloated abdomen
WARNING - Cats may technically survive without food for up to a week or two, but the process of converting fat stores into energy burdens the liver. After only 2 - 3 days of not eating, cats may develop a severe condition called Hepatic Lipidosis, or fatty liver. Without treatment, these cats usually don't start eating again on their own.
Treatment
Often, treatment will begin while the vet is still determining exactly what is causing the loss of appetite. There are a handful of different methods to treat the condition.
Slippery Elm
The herb Slippery elm contains mucilage, a substance that becomes a slick gel when mixed with water. It coats and soothes the mouth, throat, stomach, and intestines. It also contains antioxidants that help relieve inflammatory bowel conditions. Slippery elm causes reflux stimulation of nerve endings in the gastrointestinal tract leading to increased mucus secretion. The increased mucus production helps to protect the gastrointestinal tract against ulcers and excess acidity.
In cats, the kidneys are indirectly responsible for controlling levels of stomach acid. Cats with chronic kidney disease are more likely to have elevated acid levels making them more prone to nausea and inappetence. Slippery Elm helps alleviate nausea and inappetence in pets suffering from non-GI illnesses, such as kidney disease. Please visit my Slippery Elm page for more information.
Fluid Therapy
Either through an IV (intravenous) or through injections under the skin (subcutaneous or sub-q), your vet will show you how to deliver fluids to your cat at home so they will continue to receive hydration. Please visit my Kidney Disease page (Treatment > Fluid Therapy) for more information.
Medication
Depending on the diagnosis, your vet will prescribe the corresponding medication to treat whatever illness your cat may have.
There are also medications available that will stimulate your cat's appetite while handling some of the other symptoms, such as nausea. The two most commonly recommended medications are: Elura (liquid) and a transdermal (in-ear) treatment Mirataz (Mirtazapine). I have had success using both of these, but Elura is formulated to be used long-term.
Feeding Tube
This method of feeding helps avoid food going through your cat's mouth, which may be especially helpful if a dental disease is the cause of loss of appetite. Liquefied or softened food can be sent directly into the pet's digestive system. It's a method that's also useful for psychological problems with food as the cat won't be able to associate any negative feelings with food being in its mouth, and instead will steadily begin to eat on its own again. A feeding tube is only considered where other treatment options have failed.
Feeding Techniques at Home
Often, when the problem is directly related to the psyche rather than any physical illness, treatment works best with mixing up the diet or changing the way your cat is fed. You can try giving food directly out of your hand or through a syringe. For the latter, please visit my Force Feeding page for more information.
Also, warming up the food may prove useful, but always check that it's not too hot. If so, just dilute with a little water.