Ivermectin for cats is a real veterinary medicine with a narrow, well-defined role: it is the active ingredient in an FDA-approved monthly heartworm preventive chewable for cats and in an FDA-approved ear-drop suspension for feline ear mites. Everything else a cat might be given ivermectin for — injectable doses for mange, for example — is off-label use that a veterinarian decides on and doses personally.

The danger is not ivermectin itself, which has a wide safety margin at feline doses. The danger is arithmetic. Cat doses are measured in micrograms per kilogram, while livestock products are concentrated for animals hundreds of times a cat's size, and confusing the two has killed cats. If you are reading up on where human ivermectin can legally be bought in order to dose a cat yourself from a cattle or horse product, that is the single scenario veterinary toxicologists warn about most. Those livestock formulations are labeled for animal use only, are not approved for people, and are not made to be measured into a 9-pound cat.

Key takeaways

  • Cat doses are in micrograms. The approved monthly heartworm dose is roughly 24 mcg/kg — thousands of times smaller than a livestock dose by volume.
  • Two ivermectin products have been FDA-approved specifically for cats: a monthly oral chewable for heartworm and hookworm, and a 0.01% ear suspension for adult ear mites.
  • Off-label injectable use for mites and mange (200–400 mcg/kg) exists in the veterinary literature but is a veterinarian's call, not a home procedure.
  • Overdose signs are neurologic — dilated pupils, wobbliness, blindness, tremors, collapse — and can appear within a few hours.
  • State laws passed in 2025 that allow over-the-counter sales of human ivermectin do not change how veterinary products are sold or make them safe to guess at for cats.

Is ivermectin safe for cats?

A veterinarian's gloved fingers gently folding back a cat's ear to examine the ear canal for ear mites

At correct feline doses, yes — with caveats. A toxicology brief published for veterinary practitioners notes that ivermectin has a wide margin of safety in all sizes and breeds of cats when the right preparation and recommended dose are used, and stresses that the dose for cats must be in micrograms, not milligrams, per kilogram. That single sentence is the whole safety story in miniature.

Where safety collapses is at high doses. In a case series published in the Journal of Veterinary Emergency and Critical Care, twenty adult cats were accidentally given a 4 mg/kg subcutaneous overdose of ivermectin; six of the sixteen that received only a single bolus of intravenous lipid emulsion went on to develop signs of intoxication, and cats with a low body condition score had more severe signs. That accidental dose was in milligrams — the kind of error that happens when someone reaches for a livestock concentration.

Kittens and thin cats

Very young kittens and underweight cats are the least forgiving patients. The approved oral chewable is labeled for cats six weeks of age and older, and the approved otic suspension for kittens four weeks and older. Below those ages, and in cats that are debilitated, there is no margin to give away.

Drug interactions

Ivermectin has been used alongside routine vaccines, antibiotics, steroids and other parasiticides without trouble. But veterinary sources flag caution when a cat is also receiving benzodiazepines, ketamine, erythromycin, spinosad, or certain antifungal drugs — all of which can change how much ivermectin reaches the brain. Your vet needs the full medication list before dosing.

Veterinary uses in cats

A tiny cat-sized chewable tablet and a digital gram scale next to a large livestock dewormer syringe, showing the difference in scale

Ivermectin is a macrocyclic lactone that paralyses and kills a range of internal and external parasites. In cats, the uses fall into two groups: the approved ones and the off-label ones.

Approved uses

The FDA-approved oral chewable for cats is indicated to prevent feline heartworm disease by eliminating the tissue stage of Dirofilaria immitis larvae for 30 days after infection, and for removal and control of adult and immature hookworms (Ancylostoma tubaeforme and A. braziliense). FDA's review summary for the product concluded that ivermectin at the minimum 24 mcg/kg dose was effective against hookworm infections across multiple trials. An ivermectin otic suspension at 0.01% was approved to treat adult ear mite (Otodectes cynotis) infestations in cats and kittens four weeks and older — though as dvm360 notes, efficacy against mite eggs and immature stages was not proven, and safe use in breeding, pregnant or lactating cats was not evaluated.

Off-label uses

The veterinary toxicology literature describes extra-label ivermectin for ectoparasites: a single 200 mcg/kg subcutaneous dose has been used for ear mites, 400 mcg/kg subcutaneously is considered effective against Notoedres cati (feline mange), and it has been used for Cheyletiella infestations, especially in catteries. Note that the same source points out an approved topical product exists for ear mites — meaning the injection is a fallback, not a first choice.

Cats are dosed very differently from other species. If you keep more than one kind of animal, the differences between ivermectin dosing in dogs and in cats are large enough that products should never be shared between them.

Dosage and formulations

An amber glass injectable ivermectin bottle with a plain unlabeled cap and a fine syringe on a stainless tray in a farm clinic

Here is how the numbers actually compare. Doses below are what published labels and the veterinary literature describe; they are reference figures, not instructions.

Use Form Dose described Status
Heartworm prevention + hookworm control Oral chewable Minimum 24 mcg/kg (10.9 mcg/lb) monthly; 165 mcg chewable for cats 5–15 lb FDA-approved for cats; prescription
Adult ear mites 0.01% otic suspension 0.5 mL per ear, one ampule per ear FDA-approved for cats; prescription
Ear mites Injectable, subcutaneous 200 mcg/kg single dose Off-label
Feline mange (Notoedres cati) Injectable, subcutaneous 400 mcg/kg Off-label

For the chewable, the labeled schedule is one 165 mcg chewable monthly for cats 5 to 15 lb, with a veterinarian consulted for cats over 15 lb, and administration at monthly intervals during mosquito season. Cats under 5 lb are covered by a smaller 55 mcg chewable.

Why livestock products are the wrong tool

A 1% cattle injectable contains 10,000 mcg of ivermectin per milliliter. A 10-pound (4.5 kg) cat's monthly preventive dose is about 109 mcg — roughly one-hundredth of a millilitre. No household syringe measures that reliably, and dilution introduces its own errors. Equine dewormer is worse still: a single syringe of 1.87% equine ivermectin paste is calibrated for a 1,250-pound animal, and the same volume problem applies to a topical pour-on used in cattle. All of these are labeled for animal use only in the species named on the carton, are not approved for human use, and are not approved for cats.

Warnings and side effects

A veterinary receptionist's hands passing a small paper bag of prescription cat medication across a counter to a client's hands

At label doses, side effects in cats are uncommon. At high doses, the problem is neurologic, because ivermectin crosses into the central nervous system.

Signs of ivermectin toxicosis

  • Dilated pupils (mydriasis) and apparent blindness
  • Ataxia — stumbling, wobbling, loss of coordination
  • Lethargy, depression, weakness, drooling
  • Tremors, seizures, recumbency, coma; death in severe cases

Veterinary sources report that signs may appear within two to three hours of an overdose, though they can develop more slowly in milder cases, and that a cat suspected of ivermectin overdose needs immediate veterinary attention.

What treatment looks like

There is no specific antidote. Care is supportive, and intravenous lipid emulsion is sometimes used for fat-soluble toxins like ivermectin — with variable results. VETgirl describes a case in which no dramatic improvement followed lipid therapy, but the cat was discharged 72 hours after ingestion with mild persistent ataxia on supportive care. In the overdose series above, additional lipid emulsion was given until clinical signs resolved. If you suspect an overdose, call your veterinarian or the ASPCA Animal Poison Control Center rather than waiting to see what happens.

A note about people

FDA and the American Veterinary Medical Association have both warned that animal ivermectin products are highly concentrated — especially large-animal products — that high doses can be toxic in humans, and that these products contain inactive ingredients never evaluated for human use. Veterinary ivermectin is for the animal species on the label, and nothing in this article is a basis for a person taking it.

Where to buy it

The ivermectin products approved for cats are prescription items. Veterinary pharmacies list the oral chewable as a prescription heartworm preventive, typically sold in up to a 12-month supply per cat per year, and your veterinarian will generally want a heartworm test before starting a cat on preventives. That prescription requirement is the practical control that keeps feline dosing in the microgram range where it belongs.

Availability

Availability of the approved feline products has been uneven, and online veterinary pharmacies list the ivermectin otic suspension as in or out of stock at different times. Your veterinarian or a licensed veterinary pharmacy can tell you what is available now. If that product is out, a veterinarian can select among other approved feline ear-mite treatments — an important reason to have the diagnosis confirmed rather than treating a suspected mite problem blindly.

Pricing

GoodRx tracks some pet medications alongside human drugs, and notes that pet medications come in forms and dosages specifically for pets. For the feline heartworm chewable, GoodRx's listing indicates the product is FDA-approved but not stocked in retail pharmacies in its database, so pricing generally comes from your veterinary clinic or a licensed veterinary pharmacy instead. For comparison, the canine version has been listed at around $90 for a common package size with a coupon. Expect clinic pricing to vary by region and package count.

What the 2025 state laws did and did not change

Several states loosened access to human ivermectin during 2025. Pharmacy Times reported that Arkansas passed SB 189 and Act 396 on March 25, 2025, and Idaho passed SB 1211 on April 14, 2025, with both states' acts stating that ivermectin suitable for human use may be sold without a prescription or consultation. Tennessee had acted earlier, in 2022, and Louisiana and Texas followed under differing models, with the Texas law taking effect December 4, 2025. Reporting also notes that none of these laws include dosing guidance, and that pharmacies remain free to decide whether to stock the drug — so legal permission does not guarantee availability.

None of this applies to cats. These statutes concern human-labeled products for human use; they do not reclassify veterinary drugs, do not authorize animal dosing, and do not make a human tablet appropriate to cut up for a cat. The state-law details on this page were last verified on September 26, 2026. Prices and product availability change constantly — treat the figures above as estimates, confirm both with your veterinarian, and confirm state law with your state board of pharmacy before relying on any of it.

Frequently asked questions

What is the correct cat ivermectin dosage?

For the approved oral heartworm chewable, the label specifies a minimum of 24 mcg/kg (10.9 mcg/lb) monthly, delivered as a 165 mcg chewable for cats 5 to 15 lb. Off-label injectable doses in the literature run 200 mcg/kg for ear mites and 400 mcg/kg for Notoedres cati. Only a veterinarian should calculate and administer an off-label ivermectin cat dose.

Can I use ivermectin for cat ear mites at home?

Not with a livestock product. There is an FDA-approved 0.01% ivermectin otic suspension for adult ear mites in cats and kittens four weeks and older, dosed as one 0.5 mL ampule per ear — but it is a prescription product, and your veterinarian or veterinary pharmacy can confirm whether it is in stock. Ear mites also look a lot like other causes of itchy, discharging ears, so a vet exam is worth the visit.

Is ivermectin approved for cats at all?

Yes, for two specific purposes: monthly heartworm prevention with hookworm control, and adult ear mites. Other feline uses are off-label, which is legal for a veterinarian but means the dose, interval and safety data are not on any label.

How fast do overdose signs appear?

Often within two to three hours, though milder cases can develop more gradually. Watch for dilated pupils, stumbling, apparent blindness, tremors and collapse, and treat any suspicion as an emergency.

Can I give my cat my dog's heartworm preventive?

No. Canine and feline products differ in strength and in which parasites they cover, and dog products may contain additional active ingredients not intended for cats. Dose per species, per label, per body weight.

Sources