Appetite Loss & Nausea

Appetite loss and nausea are among the most common and distressing problems in cats with chronic kidney disease. Up to 92% of CKD cats experience some degree of reduced appetite, and it is the single factor owners most often associate with a decline in their cat’s quality of life. Getting on top of these symptoms is not just about comfort. A cat who refuses to eat is at risk of rapid deterioration, and finding and treating the underlying cause can make a measurable difference to how your cat feels day to day.

This page covers why appetite loss and nausea happen, how to recognize them, and what can be done. From simple adjustments at home through to prescription medications your vet can prescribe.

As kidney function declines, waste products that the kidneys would normally filter out begin to accumulate in the bloodstream. This buildup is called uremia, and the waste products themselves are known as uremic toxins. These toxins affect an area of the brain called the central chemoreceptor trigger zone, which sits just outside the blood-brain barrier and is particularly sensitive to circulating compounds. When this area is stimulated, it produces feelings of nausea and suppresses the desire to eat.

Inappetence and weight loss are more common than vomiting in IRIS CKD Stages 3 and 4, and it is increasingly recognized that nausea, even without visible vomiting, may be the main driver of poor appetite in these cats. A cat can feel persistently nauseated without ever actually vomiting, which makes the problem easy to underestimate.

A second mechanism involves gastrin, a hormone that stimulates stomach acid production. The kidneys normally clear gastrin from the body, but in CKD this process is impaired and gastrin levels rise. This was long thought to cause gastric hyperacidity and stomach ulcers, and for many years acid-suppressing medications were routinely prescribed to CKD cats on that basis. More recent evidence has challenged this view: studies measuring actual stomach acidity in CKD cats found no consistent evidence of hyperacidity, and post-mortem examination of CKD cats found no significant stomach ulceration or inflammation. Current thinking is that uremic toxins acting on the brain are the more important driver, rather than excess acid attacking the stomach lining. Though the picture is not entirely settled, and gastric acid may still play a role in some cats.

Regardless of mechanism, the result is the same: the cat feels unwell, food smells wrong or holds no appeal, and eating becomes something to be avoided.

Cats are good at hiding how they feel, and nausea in particular can be subtle. Unlike vomiting, which is visible and unmistakable, nausea often shows up as a cluster of small behavioral signals. If you see several of the following, nausea is worth considering and worth discussing with your vet:

Appetite-related signs

• Eating noticeably less than usual, or stopping mid-meal
• Approaching the bowl, sniffing or licking the food, then walking away without eating, a classic pattern in CKD cats with uremia
• Licking the gravy from wet food and leaving the solid pieces behind (if this is new behavior rather than a lifelong preference)
• Sudden pickiness or food refusal in a cat who previously ate well

Nausea signs

• Lip licking or repeated swallowing
• Drooling (ptyalism)
• Sitting hunched up or in a meatloaf position with the belly tucked under, a sign of stomach discomfort
• Teeth grinding (bruxism)
• Yawning repeatedly
• Audible stomach gurgling
• Eating grass or other non-food items in an attempt to relieve nausea
• Pawing at the mouth
• Increased interest in water, or hovering over the water bowl without drinking normally

Signs that may indicate uremia more broadly

• Hoarseness or changes in vocalization
• Increased drinking that is new or worsening
• Lethargy or reduced activity that has appeared alongside appetite changes

It is perfectly possible for a cat to have significant nausea without any of these signs being obvious, some cats simply go quiet and stop eating. If your cat’s appetite has declined, nausea should always be considered as a possible reason, particularly if kidney values are elevated.

Appetite loss and nausea in a CKD cat are not automatically caused by uremia. Several other conditions, many of them treatable, can produce the same symptoms, and a cat may have more than one problem at once. Your vet should consider:

• High phosphorus levels – elevated phosphorus contributes directly to how unwell a CKD cat feels, and controlling it often improves appetite
• Anemia – reduced red blood cell numbers leave cats feeling weak and disinterested in food
• Dehydration – chronic dehydration worsens uremic symptoms and suppresses appetite
• Metabolic acidosis – a build-up of acid in the blood that can cause nausea and malaise
• Dental disease or mouth ulcers – pain in the mouth makes eating uncomfortable or impossible
• Pancreatitis – commonly causes nausea and appetite loss in cats, and often occurs alongside CKD
• Hypertension – poorly controlled blood pressure can cause cats to feel unwell generally
• Constipation – backed-up intestines can suppress appetite and cause discomfort
• Medications – some antibiotics, and hyperthyroidism medication in particular, can reduce appetite or cause nausea in certain cats

Treating whichever of these are present will usually produce a clearer improvement than any appetite medication alone. For example, a cat whose appetite loss is driven mainly by anemia is unlikely to respond well to anti-nausea medication but may eat much better once the anemia is addressed.

Cats who are not eating are at risk of hepatic lipidosis (fatty liver disease), a potentially life-threatening condition that can develop when a cat’s body begins breaking down fat reserves too rapidly. The American Animal Hospital Association recommends contacting your vet if your cat has not eaten for one to two days. A cat eating less than half to three-quarters of their normal food intake for two weeks is also considered at risk.

Contact your vet promptly if your cat:

• Has not eaten for 24 to 48 hours
• Has lost noticeable weight over a short period
• Seems increasingly lethargic or withdrawn alongside appetite changes
• Is showing any signs of distress, pain, or rapid deterioration

Before reaching for medication, a few simple changes can make a meaningful difference, particularly in cats with earlier-stage CKD. These carry minimal risk, cost little, and can be tried immediately.

Raise the food and water bowls

When a cat eats with the bowl on the floor, the stomach sits higher than the mouth, which can allow stomach contents to move toward the esophagus and trigger discomfort. Raising bowls to roughly 15 cm (6 inches), an upturned flower pot works well as a base, keeps the stomach lower and reduces this reflux effect. Many owners report that elevated bowls increase food intake noticeably in the first days of use.

Feed smaller meals more frequently

An empty stomach gives gastric acid more opportunity to cause irritation. Offering smaller portions more often across the day, including a meal just before bedtime, keeps something in the stomach throughout and can reduce morning nausea. An automated timed feeder overnight can help if your cat tends to be sick or reluctant to eat first thing in the morning.

Warm the food slightly

Warming wet food to just below body temperature (around 37°C / 98°F) releases more aroma, which can make food more appealing to a cat whose sense of smell has been affected by uremic toxins. Do not overheat, cats will refuse food that is too hot, and hot spots in microwaved food can cause burns.

Offer variety, but change gradually

CKD cats often become pickier over time, and rotating between several acceptable foods prevents them from fixating on one that may later be refused. However, introduce new foods alongside familiar ones rather than making sudden switches,  abrupt changes can worsen appetite loss in a cat already feeling unwell.

Slippery elm bark

This herbal supplement soothes the mucosal lining of the digestive tract and is used by some owners to reduce nausea and stomach discomfort. It can also help with both diarrhea and constipation. Inform your vet before using it, as it may affect the absorption of other medications if given at the same time.

If home measures are not enough, anti-nausea medication is often very effective and can produce a rapid and noticeable improvement. The IRIS 2023 treatment guidelines recommend treating nausea and reduced appetite in CKD cats with an antiemetic or appetite stimulant such as maropitant, ondansetron, mirtazapine, or capromorelin.

Maropitant (Cerenia)

Maropitant works by blocking neurokinin-1 (NK-1) receptors in the chemoreceptor trigger zone and vomiting center of the brain — exactly where uremic toxins are thought to exert their effects. This makes it a particularly logical choice for CKD-related nausea. It may also have some mild anti-inflammatory and pain-modifying properties.

Maropitant only needs to be given once a day. It is available as tablets (16 mg, typically broken into cat-sized doses of around 4 to 9 mg daily depending on body weight) or as an injectable solution. The injectable form stings on administration; refrigerating it beforehand and giving it into a subcutaneous fluid pocket after fluids can help. Newer injectable formulations such as Prevomax and Vetemex (available in the UK and Europe) contain a preservative that reduces injection site discomfort.

A clinical trial specifically in CKD cats found significant reductions in vomiting with maropitant, though it did not appear to improve appetite directly on its own.

One caution worth noting: the European Medicines Agency advises against using maropitant alongside calcium channel blockers such as amlodipine, which is commonly prescribed for hypertension in CKD cats. If your cat takes amlodipine, discuss the timing with your vet — spacing the two medications 12 hours apart appears to reduce the risk of interaction.

Ondansetron (Zofran)

Ondansetron works through a different mechanism, selectively blocking serotonin 5-HT3 receptors. Because it acts differently from maropitant, the two can complement each other, and some cats do better on one than the other. Your vet can help decide which to try first.

Ondansetron is available as tablets, an injectable solution, and a transdermal gel. The injectable form has better absorption than the oral form — one pharmacokinetic study found oral bioavailability in cats ranged from just 11% to 50% depending on the individual. Subcutaneous injection is effective and more predictable than oral dosing. The injectable form does sting, but less so if given after subcutaneous fluids.

Dosing frequency is often twice daily, though some cats need three or four times daily for adequate control. If twice-daily dosing is not providing enough relief, speak to your vet about increasing the frequency before increasing the dose.

One interaction to be aware of: using ondansetron alongside mirtazapine may theoretically increase the risk of serotonin syndrome. If both are used, the general recommendation is to give them at least two hours apart.

Which to choose

Both maropitant and ondansetron are endorsed by the ISFM consensus guidelines for CKD cats. Maropitant has the convenience of once-daily dosing and may be particularly well suited to the uremic nausea seen in CKD because of where it acts in the brain. Ondansetron may be preferable when vomiting is more prominent, or when concurrent pancreatitis is present. Some cats respond well to one but not the other — if the first choice is not helping adequately after an appropriate trial, it is worth asking your vet about switching or combining them.

Anti-nausea medications address the feeling of sickness that suppresses appetite, but some cats need additional help to start eating again even once the nausea is controlled. Two medications are currently licensed for use in cats as appetite stimulants.

Mirtazapine (Mirataz / oral mirtazapine)

Mirtazapine is a tetracyclic antidepressant that, at the doses used in cats, acts primarily as an appetite stimulant and has some anti-nausea properties through its blockade of 5-HT3 receptors. It is among the most widely used and well-studied appetite stimulants in cats with CKD.

A clinical trial in CKD cats found that oral mirtazapine given every other day produced significantly increased appetite, weight gain, increased activity, and reduced vomiting compared to placebo.

Mirtazapine is available as:

• Oral tablets — typically given at 1.88 mg every 48 to 72 hours. Cats with more advanced kidney disease may need longer intervals between doses, as impaired kidney function slows clearance of the drug.

• Transdermal gel (Mirataz) — applied to the inner surface of the ear flap daily. This is FDA-approved specifically for use in cats and avoids the challenge of pilling. Owner surveys find the transdermal route is generally well accepted; side effects were reported by around 20% of owners, most commonly increased vocalization, redness at the application site, or mild restlessness. The transdermal route is more expensive than oral tablets.

Because mirtazapine affects serotonin pathways, it should not be combined with other serotonergic medications without veterinary guidance, and should be separated from ondansetron by at least two hours if both are used.

Capromorelin (Elura / Eluracat)

Capromorelin is a ghrelin receptor agonist — it mimics the action of ghrelin, the body’s natural hunger-signaling hormone, triggering a feeling of appetite in the hypothalamus. It also promotes growth hormone release, which may help preserve lean muscle mass.

Elura (the US brand name) holds the distinction of being the first drug specifically approved by the FDA for management of weight loss in cats with CKD. A 2025 randomized controlled trial in 176 cats with CKD and unintended weight loss found that capromorelin produced progressive weight gain over 55 days, while cats in the placebo group continued to lose weight. The drug is available in the UK and Europe as Eluracat. The standard dose is 2 mg/kg given orally once daily (0.1 ml/kg of the oral solution).

The most common side effects observed in the CKD field trial were vomiting, hypersalivation (drooling), and reduced appetite — somewhat paradoxically, some cats appear not to tolerate it well initially. Capromorelin should not be used in cats with acromegaly (hypersomatotropism), as it stimulates growth hormone pathways.

A note on appetite stimulants and quality of life

Appetite stimulants can be very effective at getting a cat eating again, and this matters — a cat who maintains weight has a better prognosis and generally more energy and engagement. However, it is worth being thoughtful about their use. A cat who is eating because of an appetite stimulant but who is still experiencing significant nausea or discomfort may be eating despite feeling horrible rather than because they feel better. Appetite stimulants work best when used alongside — not instead of — anti-nausea treatment and management of underlying causes such as high phosphorus or anemia.

If your cat is being offered only an appetite stimulant without any assessment of the underlying cause of inappetence, it is worth asking your vet whether anti-nausea medication should also be considered.

• IRIS treatment recommendations for CKD in cats (2023). International Renal Interest Society.
• ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016). Sparkes AH et al. Journal of Feline Medicine and Surgery 18, pp219-239.
• Treatment of vomiting, nausea and inappetence in cats with chronic kidney disease. IRIS (iris-kidney.com).
• Quimby JM & Lunn KF (2013). Mirtazapine as an appetite stimulant and anti-emetic in cats with chronic kidney disease: a masked placebo-controlled crossover clinical trial. Veterinary Journal 197(3), pp651-655.
• Quimby JM et al. (2020). Assessment of compounded transdermal mirtazapine as an appetite stimulant in cats with chronic kidney disease. Journal of Feline Medicine and Surgery 22, pp376-383.
• Wofford JA, Milliken MacKinnon A & Heinen E (2025). Capromorelin promotes weight gain in cats with unintended weight loss: a randomized, masked, placebo-controlled clinical trial. Journal of Feline Medicine and Surgery 27(11).
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• ACVIM consensus statement: support for rational administration of gastrointestinal protectants to dogs and cats (2018). Marks SL et al. Journal of Veterinary Internal Medicine 32(6), pp1823-1840.
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• Oral, subcutaneous and intravenous pharmacokinetics of ondansetron in healthy cats (2014). Quimby JM et al. Journal of Veterinary Pharmacology and Therapeutics 37(4), pp348-353.