Cat Medication Dosage Calculator

The Cat Medication Dosage Calculator calculates species-specific doses for commonly prescribed feline medications using published veterinary protocols and the cat drug database.

Your Cat Is Not a Small Dog

Every year, cats die because their owners — or occasionally even their owners' well-meaning friends — assume that a medication safe for dogs can be given to a cat at a reduced dose. This assumption is lethal. Cats are not small dogs, and the differences go far deeper than body weight. Feline liver metabolism lacks several critical enzyme pathways that dogs possess, most notably the glucuronidation pathway mediated by UGT enzymes. Without these pathways, certain drugs accumulate as toxic metabolites that destroy red blood cells and organ tissue instead of being safely eliminated.

The consequences are not theoretical. A single standard 500 mg paracetamol tablet — a dose that would barely register as a concern in a 30 kg dog — will kill most cats within 24 to 48 hours. Permethrin, an insecticide found in dozens of over-the-counter dog flea treatments, causes fatal neurological toxicity in cats even at trace concentrations transferred by grooming a recently treated dog. Before using any medication or product on a cat, confirm that it has been specifically approved or prescribed for feline use. The dog medication dosage tool covers canine-specific drugs and dose ranges that should never be applied to cats.

Cat-Toxic Substances: The Danger Table

Three categories of substance account for the majority of medication-related cat poisonings. They are listed here prominently — above the calculator — because encountering the warning before calculating a dose could prevent an emergency.

If your cat has ingested any of these substances, do not wait for symptoms. Contact your veterinarian or an emergency animal poison helpline immediately. For paracetamol ingestion, the antidote (NAC) must be administered within hours to prevent irreversible organ damage. For permethrin exposure, wash the cat with lukewarm water and washing-up liquid to remove the product from the fur before transport to a veterinary hospital.

Per-Cat Dosing: When Weight-Based Arithmetic Does Not Apply

Most medications are dosed in milligrams per kilogram — the heavier the cat, the higher the dose. Several important feline medications break this pattern entirely and are prescribed at a fixed dose per cat, regardless of body weight. Understanding which drugs use per-cat dosing prevents dangerous miscalculation.

Methimazole (Felimazole), the standard treatment for feline hyperthyroidism, is dosed at 1.25 to 2.5 mg per cat twice daily as a starting dose. Whether the cat weighs 3 kg or 8 kg, the initial dose is the same — titration is guided by blood monitoring of serum T4 levels, not by body weight. Mirtazapine, an appetite stimulant used for cats with CKD or cancer-related inappetence, follows the same principle: 1.88 mg per cat every 48 hours (a quarter of a standard 7.5 mg human tablet). The 48-hour interval is critical because cats metabolise mirtazapine far more slowly than dogs or humans — daily dosing risks serotonin syndrome. Amlodipine (Norvasc), the first-line treatment for feline hypertension, is dosed at 0.625 to 1.25 mg per cat once daily, again without weight adjustment.

The calculator flags these medications and displays the per-cat dosing guidance instead of calculating a weight-based range. If a per-cat medication appears in your results, the number your vet prescribes will not change if your cat gains or loses weight — the dose is adjusted based on blood test results and clinical response at follow-up appointments.

Feline NSAID Use: A Narrower Safety Margin

Non-Steroidal Anti-Inflammatory Drugs are among the most commonly prescribed veterinary medications, but their use in cats is far more restricted than in dogs. Cat meloxicam doses (0.05 to 0.1 mg/kg) are half to one-quarter of dog doses (0.1 to 0.2 mg/kg), and long-term oral meloxicam use in cats is not approved in many jurisdictions due to the risk of acute kidney injury. Robenacoxib (Onsior), a COX-2 selective NSAID with better feline safety data, is limited to a maximum of 3 consecutive days of oral use.

Before any NSAID is administered, the cat must be well hydrated and have confirmed adequate kidney function. Dehydrated cats given NSAIDs are at extreme risk of renal damage because prostaglandin inhibition reduces blood flow to already compromised kidneys. If your cat needs pain management beyond a short NSAID course, buprenorphine (an opioid administered via the buccal mucosa) and gabapentin are the more common long-term alternatives in feline practice — both of which appear in this calculator with feline age and life stage assessment context, since older cats are disproportionately affected by conditions requiring chronic pain management.

Prednisolone, Not Prednisone

A frequently misunderstood species difference: cats must receive prednisolone (the active corticosteroid), not prednisone (the inactive prodrug). Dogs convert prednisone to prednisolone efficiently in the liver. Cats perform this conversion poorly, meaning prednisone is minimally effective in feline patients. If your cat has been prescribed a corticosteroid and the label reads "prednisone" rather than "prednisolone," confirm with your vet that the correct drug has been dispensed — pharmacy substitution errors between these two similarly named drugs occur more frequently than they should.

Prednisolone is used for numerous feline conditions: allergic skin disease, inflammatory bowel disease, asthma, and as part of lymphoma chemotherapy protocols. Long-term use carries significant risks including iatrogenic diabetes mellitus (cats are more susceptible to corticosteroid-induced diabetes than dogs), immunosuppression, muscle wasting, and adrenal suppression. Tapering the dose gradually when discontinuing is mandatory to avoid adrenal crisis. Your vet will aim for the lowest effective dose, often moving to alternate-day therapy for chronic conditions.

Giving Medication to a Reluctant Cat

Cats are notoriously difficult to medicate orally. Unlike dogs, they cannot be easily tricked with food-wrapped tablets — many cats chew food thoroughly enough to detect and reject hidden medication. Several practical strategies improve compliance and reduce stress for both cat and owner.

Pill pockets designed for cats (smaller and softer than the dog versions) work for some cats when the medication is odourless. For bitter medications like metronidazole, compounded flavoured formulations or gelatine capsules that mask the taste are more effective than crushing tablets into food — crushed metronidazole causes intense hypersalivation and head-shaking that makes the cat even more resistant to future dosing. Transdermal formulations represent the least stressful option: methimazole, mirtazapine, and gabapentin can all be compounded as gels applied to the inner ear pinna, absorbing through the skin and bypassing the oral route entirely. Ask your vet about transdermal options if oral dosing is becoming a welfare issue for your cat.

For liquid medications, use the graduated oral syringe provided and administer slowly into the cheek pouch — never squirt liquid directly down the throat, as aspiration into the lungs is a genuine risk in cats, particularly those that are struggling. Wrapping the cat in a towel (a "purrito") to restrain the front legs reduces scratching and makes the process safer for both parties. More detail on species-specific feeding and medication interactions can be found in our species-specific feeding guidance section.

Worked Examples in Context

The two worked examples accompanying this calculator illustrate fundamentally different dosing paradigms. The first follows a 13-year-old hyperthyroid cat on methimazole — a per-cat dose medication where the calculator flags that weight-based arithmetic does not apply and the correct dose is found through blood monitoring. The second follows a 5 kg cat prescribed gabapentin for pre-visit anxiety, demonstrating how the mg/kg range provides a starting point but practical clinical dosing (often 100 mg per cat) may exceed the strict upper bound because gabapentin has a wide safety margin in cats.

Together, these examples reinforce that feline medication dosing requires species-specific knowledge at every step — from confirming the drug is safe for cats, to checking whether the dose is per-kg or per-cat, to selecting the administration route that the individual cat will tolerate. Reading about common household substances toxic to cats provides additional context on feline metabolic vulnerabilities beyond the medication sphere.

Glossary of Key Terms

Glucuronidation

A metabolic process in the liver in which glucuronic acid is attached to drug molecules or their metabolites, making them water-soluble for excretion via urine or bile. Dogs and humans perform glucuronidation efficiently. Cats have deficient UGT enzyme activity, particularly UGT1A6 and UGT1A9 isoforms, which means they cannot safely eliminate drugs that depend on this pathway — including paracetamol, aspirin (at repeated doses), and many phenolic compounds. This enzymatic deficiency is the single most important pharmacological difference between cats and dogs.

Methemoglobinaemia

A condition in which haemoglobin is oxidised to methemoglobin, which cannot carry oxygen to tissues. In cats, paracetamol toxicity rapidly produces methemoglobinaemia — visible as chocolate-brown or blue-tinged gums (cyanosis), laboured breathing, and lethargy. Without emergency treatment (N-acetylcysteine, oxygen, blood transfusion), the condition is fatal. The brown discolouration of mucous membranes is the hallmark clinical sign and should prompt immediate emergency veterinary care.

Per-Cat Dose

A dosing convention in which the prescribed amount is a fixed number of milligrams per animal, irrespective of body weight. Per-cat dosing is used for medications where the therapeutic range is narrow and dose titration is guided by blood monitoring (methimazole) or where the drug\'s effect plateaus at a dose that does not scale linearly with weight (mirtazapine, amlodipine). Attempting to calculate a per-cat dose using mg/kg arithmetic will produce incorrect results.

Oral Transmucosal Administration

A drug delivery route in which medication is placed against the buccal mucosa (inside the cheek) or sublingual mucosa (under the tongue), where it absorbs directly into the bloodstream through the mucous membrane. Buprenorphine is the most common feline medication given by this route — OTM administration produces reliable blood levels because feline saliva pH (8 to 9, more alkaline than dogs or humans) enhances buprenorphine absorption. Swallowing buprenorphine renders it largely ineffective due to extensive first-pass hepatic metabolism.

Medication Safety and Broader Feline Health

Accidental overdose, administration of dog products, and drug interactions are the three most common medication-related emergencies in cats. Keeping all medications in cat-proof containers (cats can open flip-top lids that dogs cannot), storing dog flea products separately from cat products, and maintaining a list of your cat\'s current medications to show every vet who treats the animal are straightforward precautions that prevent the majority of incidents. Feline patients on multiple medications — a common situation in senior cats managing hyperthyroidism, kidney disease, and hypertension concurrently — require particularly careful oversight. For a broader view of age-related feline health considerations, the chocolate toxicity assessment for dogs demonstrates how toxic dose thresholds work across species, reinforcing why species-specific tools matter.

Dose ranges, frequency guidance, and safety data in this calculator are drawn from Plumb\'s Veterinary Drug Handbook (9th Edition), the BSAVA Small Animal Formulary (10th Edition), and the Merck Veterinary Manual pharmacology chapters. All medication content on this page is flagged for veterinary review and will be updated if source guidelines change or new feline safety data emerge.