Why Is My Cat Not Eating? Causes and When to Worry

The hepatic lipidosis risk: why this matters for cats specifically

Hepatic lipidosis (fatty liver disease) is the most common liver disease in cats and develops specifically from not eating. When a cat stops consuming food, the body mobilizes fat from fat deposits to use as energy. In cats, this process overwhelms the liver's processing capacity, causing fat to accumulate within liver cells and impairing liver function. Clinically significant hepatic lipidosis can develop within 2-7 days of appetite loss, and it is potentially fatal without treatment.

This makes anorexia in cats distinctly more urgent than in dogs. A healthy adult dog can safely fast for 1-3 days without significant risk. A healthy adult cat should not fast for more than 24-48 hours before veterinary evaluation is warranted. Overweight cats are at higher risk because they have more fat available to mobilize. Signs of developing hepatic lipidosis: jaundice (yellowing of the skin inside the ears or whites of the eyes), lethargy, drooling, and vomiting. At this stage, hospitalization and nutritional support via feeding tube are typically required.

Common causes by duration and context

Appetite loss lasting 12-24 hours with no other symptoms: stress from a household change (new pet, moved, houseguest), recently changed food, mild upset from eating something unusual, or heat (cats eat less in very warm weather). Monitor closely; offer familiar food in a quiet location. Appetite loss with other symptoms (sneezing, nasal discharge, lethargy, vomiting, or behavioral changes): likely illness. Do not wait -- contact your vet. Upper respiratory infections (cat flu) cause nasal congestion that blocks the cat's ability to smell food; cats rely heavily on smell to locate and assess food. A congested cat often refuses food entirely not because it isn't hungry, but because food doesn't smell like food.

Appetite loss in a cat over age 8: hyperthyroidism (paradoxically sometimes causes weight loss with maintained or increased appetite), kidney disease (causes nausea and reduced appetite), dental disease, or cancer. These require bloodwork and clinical examination to distinguish.

What not to do

Do not try to force-feed a cat using a syringe or by putting food in its mouth -- this creates a food aversion that can make the problem significantly worse and longer-lasting. Do not change to an entirely different food as an enticement without understanding why the cat stopped eating -- if there is an underlying illness, the focus should be on the illness, not finding a more appealing food. Do not assume the cat will "eat when it's hungry enough" -- this is false for cats. They will not eat when ill enough, and the delay worsens outcomes.

Appetite stimulants and assisted feeding

Mirtazapine (oral tablet or transdermal gel applied to the ear skin) is a safe and effective appetite stimulant for cats, available by veterinary prescription. It is appropriate for short-term use while the underlying cause is investigated. Cyproheptadine is an alternative with appetite-stimulating effects. These medications address the symptom; they do not treat the underlying cause. Use them as a bridge to getting adequate calories in while working on diagnosis.

If a cat has not eaten for 3+ days and is in veterinary care, a nasoesophageal or esophagostomy feeding tube provides consistent caloric delivery, which is the primary treatment for early hepatic lipidosis. Recovery from hepatic lipidosis with appropriate nutritional support is good (70-80% survival), but requires sustained treatment over several weeks.