The best appetite stimulant for most cats is mirtazapine, available as an FDA-approved transdermal ointment called Mirataz. It’s the only medication with strong evidence for improving both appetite and weight in cats across a range of conditions. For cats specifically losing weight from chronic kidney disease, a second FDA-approved option called Elura (capromorelin) has also proven effective. The right choice depends on your cat’s underlying condition, how easy it is to medicate them, and what your veterinarian recommends.
A cat that stops eating for multiple days in a row risks developing hepatic lipidosis, a potentially fatal liver condition where the body floods the liver with fat reserves. This is why appetite loss in cats is treated more urgently than in dogs, and why having effective options matters.
Mirtazapine: The Most Widely Used Option
Mirtazapine is the most broadly supported appetite stimulant for cats. The transdermal form (Mirataz) is applied as a 1.5-inch ribbon of ointment to the inner ear flap once daily for 14 days, alternating between left and right ears. This delivery method avoids the challenge of pilling a cat that already doesn’t want to eat. Scientists don’t fully understand the exact mechanism behind its appetite-boosting effect, but it likely works through multiple pathways, including anti-nausea properties. Research from the International Renal Interest Society found that mirtazapine improved appetite, reduced vomiting, and increased weight gain in cats with chronic kidney disease.
The most common side effects of the transdermal ointment are mild: skin irritation at the application site, behavioral changes like vocalization or hyperactivity, and occasional vomiting. Drowsiness can also occur. These side effects are generally manageable, but overdose is a real concern. A study of 84 cats exposed to toxic doses of mirtazapine found vocalization in 56% of cases, agitation in 31%, and vomiting in 26%. At higher overdoses, cats can develop tremors, a rapid heart rate, rapid breathing, and signs consistent with serotonin syndrome, a dangerous condition involving muscle hyperactivity, elevated body temperature, and extreme agitation. The standard dose prescribed by your vet has a wide safety margin, but accidental ingestion of extra medication (such as a cat chewing a tube of the ointment) can quickly become serious.
Capromorelin: For Cats With Kidney Disease
Elura (capromorelin) is an oral liquid FDA-approved specifically for managing weight loss in cats with chronic kidney disease. It works by mimicking ghrelin, the hormone that signals hunger. In a 56-day clinical trial, cats receiving Elura gained weight while the control group continued to lose it. A six-month safety study showed weight gain at every dose tested, with cats on higher doses eating noticeably more food.
The most common side effects are vomiting, diarrhea, increased thirst, and excess salivation. For cats that need long-term appetite support due to kidney disease, capromorelin offers a targeted option. It’s given as a once-daily oral solution, which is easier than a pill but still requires getting liquid into a cat’s mouth. It’s worth noting that capromorelin is approved for dogs under a different brand name (Entyce) for general appetite stimulation, but in cats, the approved use is limited to kidney disease-related weight loss.
Cyproheptadine: The Older Alternative
Before mirtazapine and capromorelin gained FDA approval for cats, cyproheptadine was the go-to appetite stimulant. It’s an antihistamine that happens to increase appetite as a side effect. It’s given orally, typically twice daily, and is still used off-label when newer drugs aren’t an option or aren’t tolerated.
Cyproheptadine has notable drawbacks. It can lower the seizure threshold, making it a poor choice for cats with epilepsy or those on seizure medications. Some cats develop central nervous system excitement and aggressive behavior on the drug. Its effectiveness is also less consistent than mirtazapine. Most veterinarians now consider it a second-line option, but it remains inexpensive and widely available.
Vitamin B12 Deficiency and Appetite
One often-overlooked factor in feline appetite loss is vitamin B12 (cobalamin) deficiency, which frequently occurs alongside gastrointestinal diseases and conditions that also cause poor appetite. Anorexia is one of the most commonly described signs of cobalamin deficiency in cats. The relationship works in both directions: sick cats eat less, which worsens their B12 levels, which further suppresses appetite.
What makes B12 supplementation particularly interesting is that anorexic cats with low cobalamin levels often start eating again once supplementation begins, and their appetite can drop off again if the supplements stop, even after blood levels normalize. Your vet can check B12 with a simple blood test. Treatment typically involves injections given weekly for six weeks, then every two weeks for another six weeks, then monthly. Oral supplementation with daily tablets has also been shown to raise levels effectively in cats with GI disease. B12 won’t replace a dedicated appetite stimulant in every case, but correcting a deficiency can make a meaningful difference on its own or alongside other treatments.
Steroids as Appetite Stimulants
Prednisolone, a corticosteroid, reliably increases appetite in cats and is sometimes used for this purpose when a cat is also being treated for inflammation, allergies, or certain cancers. Increased appetite is one of its most predictable effects. However, prednisolone is rarely a good first choice purely for appetite stimulation. Long-term use carries significant risks: diabetes, muscle wasting, liver changes, a distended abdomen, weakened immunity, and gastrointestinal ulceration. Short courses may be reasonable in specific clinical situations, but for straightforward appetite loss, mirtazapine or capromorelin are safer and more targeted.
Why Nausea Treatment Matters Too
Appetite stimulants work best when nausea isn’t actively suppressing the desire to eat. Many conditions that cause appetite loss in cats, particularly kidney disease, also cause nausea. Anti-nausea medications can help break this cycle, though they don’t directly stimulate appetite on their own. One commonly used anti-nausea drug was shown to significantly reduce vomiting in cats with kidney disease but had no measurable effect on appetite, weight, or activity. Mirtazapine is unusual in that it addresses both nausea and appetite simultaneously, which is part of why it’s so effective for cats with kidney disease.
If your cat is turning away from food and also showing signs like lip-licking, drooling, or repeated swallowing, nausea is likely part of the problem. Treating just the appetite without addressing nausea can leave you fighting an uphill battle.
Simple Changes That Can Help
Medication isn’t always the first step. Cats rely heavily on smell to decide whether food is appealing, and their sense of smell is far more developed than ours. Warming food to just below body temperature increases its aroma and can make it more enticing. Cats generally prefer foods that are high in moisture, fat, and protein, with acidic flavors and strong scents.
There’s a useful counterpoint to the warming advice, though. Cats that have developed a learned food aversion, associating certain smells or tastes with feeling sick, may actually accept chilled food better because it has less aroma. If your cat approaches the bowl and then backs away, this is worth trying. Offering food in a different room, using a different dish, or having a different person do the feeding can also help break negative associations. Cats are creatures of routine, but when that routine has been linked to nausea or discomfort, disrupting it can work in your favor.
Keep mealtimes quiet and low-stress. If you have multiple pets, feed the anorexic cat separately so they’re not competing or feeling pressured. These adjustments won’t fix a medical cause of appetite loss, but they can complement medication and make the difference between a cat that nibbles and one that finishes a meal.