My Pet Won’t Eat . . . Why?

There can be a number of potential causes for an animal not to eat. Dr. Google lists about 25 different reasons for inappetence in the dog and cat. Dental disease seems to be one of the top instigators in search engine discovery, but general maladies such as cancer, sickness, stress, the food itself, and specific ones such as parasites, poisoning and pancreatitis are listed along with others. In the younger animal, I would add gastrointestinal foreign bodies. Each may have some influence depending on the severity, and I do not necessarily want to discount any of them. However, in the elderly cat and dog, I believe nausea is one of the main reasons most do not want to eat, whatever the instigating cause. If you have ever had an upset stomach, you can relate as to why this would diminish your pet’s appetite. Nausea, in the elderly animal, can occur in many different disease situations, but the most common in my world seem to be kidney disease, pancreatitis and age related gastrointestinal problems. GI symptoms can be caused by kidney disease and pancreatitis, but may be spontaneous in the elderly animal. 

A significant number of older animals have some degree of chronic kidney disease, and many veterinarians refer to this as kidney failure. To me, failure denotes an extremely pessimistic viewpoint, and I believe, when a person hears that their pet is in “kidney failure” they immediately think of euthanasia. Kidney disease, in most cases, and especially in the elderly animal, is not a treatable condition. However, we can support them in many different ways (See the article on Kidney Insufficiency). With advanced kidney disease, there are elevations in toxins that the kidneys would ordinarily filter out of the blood. That is their purpose, but when the kidneys are not able to filter the blood properly, the animal begins to not feel well. It is not a painful disease, but the pet is often lethargic and doesn’t want to eat, and in many cases, they are nauseous, which diminishes their desire to eat. 

Prescription diets can also contribute to the animal’s lack of interest in eating. Most, if not all of these specialized diets are deficient in certain ingredients that may make them less palatable. Kidney diets, as an example, are often one of the instigators for inappetence in the affected dog. There is a lot of research that has gone into the development of kidney diets, and veterinarians will often tell their clients that the kidney diet is a necessary part of treating kidney disease, when in fact, the diets are only supportive in their approach to treatment. It is much more important  for the animal to eat than it is to be restricted to a diet they won’t eat. This is true for any of the prescription diets with few exceptions. 

Using food to give medications may lead to a food aversion, especially in cats and it becomes even more of a problem in the older cat. Unfortunately, as cats and dogs get older, they often develop problems that require medication, and in many cases, multiple medications. Giving a cat a pill, or multiple pills can be a challenge at best, and impossible at worst. Liquid medications are even more problematic for most cats. People will often resort to mixing medication in the food thinking that this will be a good way to administer the medication(s). It may work at first, but rarely will work for an extended period of time. Dogs seem to be easier to trick into eating something with a pill inside. However, if the dog is a picky eater (see below under pancreatitis), this approach may not work for long or at all. I have had many instances where the caregiver had to stop all medication. I’m not advocating that, but the pet can lose trust in the caregiver when continually traumatized during medication administration. That distrust can affect the human animal bond. Fortunately, many medications can be compounded into various forms that can be administered more easily, and some can be formulated into transdermal products that can be applied to the ear or skin. Please check with your veterinarian to see if there can be a better approach to giving medication if you are having a problem. 

Another relatively minor cause for a diminished appetite can develop when having to change diets. People are told to just mix a little of the new food with the old and gradually increase the new and decrease the old diet over time. This sounds like a good way to change diets, but it can lead to a food aversion similar to putting medication in the food. It’s actually better to place a small amount of the new diet in a bowl next to the original one. This allows the pet to adjust to the food by choice rather than by being forced to eat the mixture. 

Pancreatitis, I believe, is under diagnosed, but relatively common in the older animal. Studies have shown that over 50% of dogs have some degree of either an acute or chronic form of the disease, and I believe a greater percentage of elderly dogs (and cats, too) have pancreatitis that is causing them to not eat due to nausea or discomfort. In my conversations with pet caretakers seeking end of life care, few veterinarians seem to consider pancreatitis when they are performing routine or necessary blood testing in the aged animal. In the veterinary world at the present time (2024) there are two main veterinary laboratories: IDEXX and VCA Antech. This is an important consideration because IDEXX panels do not routinely test for pancreatitis, especially the in-house laboratories. VCA Antech’s major panels do test for pancreatitis. Some hospitals use an in-house SNAP test for pancreatitis, but in my experience those tests are notoriously inaccurate. There may soon be a new in-house test that should be more accurate, however. Unfortunately, treatment for pancreatitis is usually supportive in nature, but if we know an animal has an inflamed pancreas, then the support can be more directive in its application. Severe cases in the dog that require hospitalization can now be treated with a daily injection (for 3 days) of a medication called Panoquell-CA1. At this time the cost is around $800 per injection. It has been shown to be quite effective, but the expense may be a problem for some clients. 

End of life, the actual time the animal is preparing for death, certainly can lead to inappetence, but is almost always accompanied by “not drinking.” In fact, that is a “given.” When animals are nearing death they are instinctive about what to do. Not eating AND not drinking are major turning points for life to shut down and end (life usually ends for all warm blooded creatures in 5-7 days when they stop eating AND drinking). However, just because an animal stops eating does not mean they are at death’s door. It can mean that, but in my experience it is often not the case as I mentioned earlier in this missive. Inappetence leading to death is a long, drawn out process. 

Some relatively simple things can be tried to see if a turnaround can be accomplished. Many, if not most veterinarians will prescribe an appetite stimulant if an animal is not eating as much or not eating at all. However, the approach should be to ask why the animal is not eating. If it’s nausea they prescribe the appetite stimulant along with a medication called Cerenia (Maropitant), telling the pet caretaker it’s for nausea. Unfortunately, this medication does very little for helping with nausea. It works on the brain’s emetic (vomiting) center to help stop vomiting (it also has other uses not covered here). Vomiting can be related to nausea, but not necessarily. Some animals are nauseous but not vomiting. Ondansetron has been shown to work much better than Cerenia to help minimize or treat nausea. It is also used to stop vomiting, but Cerenia is better for that. They can be used together, if needed. 

If the underlying cause of inappetence can be ascertained and treated, then the appetite stimulant is usually not needed because the pet will begin eating again. Other helpful supportive treatments can be tried in liu of the above. Famotadine (Pepcid AC) has been very helpful in my experience. Also, medical grade CBD oil (not the hemp varieties) can be used to give the animal a “sense of well-being, and seems to have some anti-nausea effects as well.

Strangely, in some forms of progressive dementia, the animal literally forgets how to eat. Once food is placed in their mouth, they will chew and swallow. This becomes a labor of love and is an intensive and time consuming process. Is it worth it? Each caretaker will need to make that decision. 

In some cases when inappetence has occurred for a prolonged period of time, force feeding will need to be done until the pet starts eating again. Cats in certain instances will develop Hepatic Lipidosis, or fatty liver syndrome. In most casesM these cats are somewhat overweight, and when they stop eating, for even 3-4 days, the liver will be overloaded with fat breakdown products, and fatty liver syndrome will develop. It’s difficult to diagnose in the early stages, and will either require the placement of a feeding tube, or force feeding until the liver cleanses itself of the fat deposits.