Cat medication dosage: how vets work it out and why it matters

Cat medication dosage is one thing you should never guess. Your vet sets the dose for your cat, and the right amount depends on the cat, the drug and the reason it’s given. This guide explains how doses are worked out, so you understand the label and know what to ask. It doesn’t give doses for any medicine, because only your vet can do that safely.

How do vets work out a cat medication dosage?

A vet weighs several things before deciding on a dose:

The FDA notes that if a cat has kidney or liver disease, the vet has to be especially careful with some drugs, such as anti-inflammatory pain relievers. That’s one reason your vet may want blood tests before and during treatment.

Why does my vet weigh my cat every time?

Weight-based dosing means the dose is calculated from your cat’s body weight. The AAFP’s guide for cat owners explains that the correct dose of many medicines depends on body weight, and that a cat who has lost or gained weight may need a different dose.

If you think your cat’s weight has changed, ask for a weigh-in at the next visit. The AAFP suggests an infant scale if you want to track weight at home. You can also check body shape with our body condition score tool.

Why can’t cats take the same doses as dogs or people?

Cats are not small dogs, and they’re not small people. Their liver handles many drugs in its own way.

One of the liver’s main clean-up routes is called glucuronidation. It attaches a sugar-based molecule to a drug so the body can flush it out. A 2013 review of feline drug metabolism found that cats carry a broken copy of a key gene for this process, called UGT1A6. As a result, cats clear some drugs much more slowly than dogs or people, or turn them into harmful by-products.

• Acetaminophen (paracetamol). Cats can’t break it down safely. It damages red blood cells so they can’t carry oxygen. The FDA says it’s fatal to cats and vets never use it in them.
• Aspirin. Cats clear it much more slowly than dogs, mainly because a different clean-up pathway is also slow in cats. Vets use it very differently in cats as a result.
• Anti-inflammatory pain relievers (NSAIDs). The FDA warns that cats may have a reduced ability to break these down.

This is why a dose that’s safe for a dog or a person can be dangerous for a cat, even scaled down for size.

Can I give my cat human or dog medicine?

No, not unless your vet has prescribed that exact product for your cat.

• Human medicines come in strengths made for people, and some contain ingredients that are toxic to cats. The FDA reports that nearly half of all calls to the Pet Poison Helpline involve pets that swallowed human medicines. See our guide to human medications toxic to cats.
• Dog medicines aren’t safe to share either. iCatCare warns that some dog flea treatments contain permethrin, which can make a cat seriously ill or kill it, even in a small amount. Using “just a little” of a dog product doesn’t make it safe.

Sometimes vets do prescribe a human drug for a cat. That’s a medical decision made for that cat, with a dose worked out by the vet.

What is a compounded medication?

A compounded medication is one a pharmacist or vet has mixed or changed to suit an individual animal. The FDA describes it as combining, mixing or altering ingredients to make a medicine tailored to one animal’s needs. For cats, that might be:

• A flavored liquid or treat instead of a bitter tablet
• A gel rubbed on the ear flap and absorbed through the skin

Compounding can make medicating much easier. The FDA points out that compounded drugs are not FDA-approved, so they haven’t been reviewed for safety, effectiveness or labeling in the way approved drugs have. Only use compounded products your vet has ordered. Follow the pharmacy’s label for storage and dose, and check with your vet if the new product looks or smells different from the last one.

Can I split or crush my cat’s tablets?

Only if your vet or pharmacist says so. iCatCare notes that some tablets have a special coating and must be given whole, and some shouldn’t be handled at all once split or crushed.

If your vet does ask you to give part of a tablet, iCatCare suggests a pill splitter, which divides tablets accurately. Ask whether a different strength or a liquid would avoid splitting altogether. For tips on the giving part, see how to give a cat a pill.

How do I measure liquid medicine accurately?

• Use the syringe or dropper that came with the medicine. The AAFP notes your vet can show you how to draw up the right amount.
• Shake the bottle if the label says so. The FDA explains that some liquids settle, and shaking spreads the medicine evenly so each dose is the same.
• Read the units carefully. The FDA has reported overdoses caused by misread labels, such as “mcg” mistaken for “mg”, which is a thousandfold difference. If anything on the label is unclear, call the clinic or pharmacy before giving it.

What should I do about a missed dose?

Call your vet or check the instructions they gave you. The FDA explains that the right answer depends on the medicine: some need to be given at evenly spaced times, and your vet can tell you when to give the next one.

Never give two doses at once to catch up. If you gave too much by mistake, call your vet right away. If your cat vomited or spat out a dose, don’t simply repeat it, because some of it may already have been absorbed.

Why should my cat finish the course?

Many medicines only work if the level in the blood stays high enough for long enough. The FDA notes that skipping doses or stopping an antibiotic early can let an infection return, or leave bacteria that no longer respond to that drug. Other medicines, such as the steroid prednisolone, must be tapered down slowly rather than stopped. Always ask your vet before stopping anything, even if your cat seems better.

How should I store my cat’s medicines?

The FDA’s advice for storing pet medicines:

• Keep them in the original container with the label and your cat’s name clearly readable
• Store them securely. Cats jump and climb, and pets can chew through pill bottles and blister packs. Child-safe doesn’t mean pet-safe
• Keep pet and people medicines apart, so nobody gives the wrong one
• Follow the storage instructions. Some need the fridge, some room temperature, some darkness
• Get rid of old medicine safely, ideally through a drug take-back program

Flavored pet medicines can tempt a cat to eat a whole supply at once, so treat them like any other medicine.

Should I keep a medication log?

Yes, especially if your cat takes more than one medicine or several people share the job. A simple log prevents missed and doubled doses. Note:

• The date and time of each dose, and who gave it
• The medicine name and strength, copied from the label
• Anything unusual, like vomiting, refusing food or spitting out the pill
• Your cat’s weight when it’s checked

Bring the log to rechecks. It helps your vet judge whether the dose is working and spot side effects early. For more drug guides, browse our cat medications guides.

Written by the CatsMed Team from the sources above. Reviewed by Dr. Jarod Grantland, DVM. It isn’t a substitute for seeing a vet. See how we research.