CBD Oil for Cats: Dose, Liver Risk, Label Reality

CBD is not a first-line treatment for anything in cats. The most defensible claim is narrow. In a 26-week oral tolerability trial, healthy cats given 4 mg/kg of CBD per day stayed clinically normal, but roughly one cat in ten developed raised liver enzymes, and the drug sits badly in a species that clears it slowly. Add a market where labels are often wrong and THC creeps in, and the honest position is: possible under veterinary supervision, never casual.

What the 26-week data actually shows

The study design matters more than the headline. Cats received 4 mg/kg per day by mouth for 26 weeks, with physical exams, bloodwork and owner diaries throughout. No deaths and no serious events were attributed to the drug. Loose stool and occasional vomiting appeared in a minority, usually in the first two weeks and usually self-limiting. The finding that changes decisions is hepatic: about 9 to 11% of cats showed ALT rises above the reference range, most between weeks 2 and 4, and most returned toward baseline after the oil was stopped. That is a 1 in 10 liver signal at a moderate dose. It is not permission to go higher.

Why cats are not small dogs

Cats have limited glucuronidation capacity. Their UDP-glucuronosyltransferase activity is low compared with dogs, so phase II conjugation of many plant compounds runs slowly. In practice CBD's half-life in cats is around 5 to 6 hours, longer than the 2 to 3 hours reported in dogs, and clearance is slower still in kittens under 12 weeks and in cats with any liver compromise. CBD also inhibits several cytochrome P450 enzymes in laboratory work, which means it can push up blood levels of drugs that share those pathways. Twice-daily dosing is used precisely because single daily doses leave troughs, but it also means accumulation over 7 to 10 days.

ALT is the number to watch

Get baseline biochemistry before the first dose, including ALT, ALP, bilirubin and bile acids. Repeat at 2 weeks, again at 4 weeks, then every 3 months while the cat is on the product. Stop and call your vet if ALT climbs above 3 times the upper reference limit, if bile acids rise, or if any of these appear: yellow tinge to the gums or ear pinnae, orange-brown urine, appetite loss lasting more than 24 hours, or sudden lethargy. Cats hide liver disease well, so the blood test is the early warning, not the behaviour.

Labels lie more often than owners expect

Independent testing of hemp products repeatedly finds CBD content far from the label, in both directions. Some bottles contain under half the stated amount, some contain double, and a few contain almost none. Hemp-derived products may legally carry up to 0.3% THC in some jurisdictions, which sounds trivial until you run the arithmetic for a 4 kg cat eating a full dropper twice a day. Cats are unusually sensitive to THC: ataxia, dilated pupils, tremors, hypersalivation, and in bad cases hyperthermia and seizures. Veterinary poison services have reported a steady rise in THC-related calls since edible and oil products spread into households.

Dosing if a vet has signed off

Start at 0.5 to 1 mg/kg every 12 hours, hold for 7 days, and only then consider moving toward 2 to 4 mg/kg per day total. Weigh the cat on the same scale you would use for a kitten, because a 0.3 kg error at 4 mg/kg is a 20% dose error, and /tools/kitten-weight/ explains why household scales drift. Buy only products with a batch certificate of analysis showing measured CBD and THC under 0.1%. Know your concentration: at 10 mg/ml, one drop of about 0.05 ml delivers 0.5 mg, so a 4 kg cat at 2 mg/kg needs 8 mg, which is 16 drops, not 4.

Product strength	CBD per drop (0.05 ml)	Drops for a 4 kg cat at 2 mg/kg/day
5 mg/ml	0.25 mg	32 drops, split into 2 doses
10 mg/ml	0.5 mg	16 drops, split into 2 doses
20 mg/ml	1.0 mg	8 drops, split into 2 doses
50 mg/ml	2.5 mg	3 to 4 drops, split into 2 doses

Interactions and household hazards

Do not combine CBD with phenobarbital, cyclosporine, ketoconazole, clomipramine or any sedative without explicit veterinary direction, because all of them compete for the same liver enzymes. Avoid products that contain xylitol, chocolate, raisins, or essential oils such as tea tree and eucalyptus, all of which are hazardous to cats on their own. Keep bottles in a closed cupboard: a cat that chews a dropper can take 10 times its dose in one go. If the household includes an immunocompromised or herpes-positive cat, stress and illness drive flares, and /health/feline-herpes-long-term/ is a better use of your attention than an unproven oil. Raw or unregulated botanical products also carry a parasite and bacterial load worth reviewing in /health/toxoplasmosis-cats/.

When to go to the emergency clinic

• Unable to stand, swaying, or knuckle-walking on the front paws.
• Tremors that do not stop, or any seizure.
• Vomiting more than 3 times in 12 hours, or any vomiting with blood.
• Yellow gums, yellow ear flaps, or dark orange urine.
• Breathing fast at rest, over 40 breaths per minute.
• Collapse, or a temperature above 40C.

A practical checklist before the first dose

1. Ask what problem you are treating, and write down how you will measure improvement in 14 days.
2. Get baseline bloodwork including ALT, ALP, bilirubin and bile acids.
3. Buy a product with a batch certificate of analysis and a stated THC limit under 0.1%.
4. Weigh the cat, calculate drops per dose from the actual concentration, and write it on the bottle.
5. Recheck liver values at 2 weeks and 4 weeks, and stop at the first abnormal result.

The realistic verdict: CBD is not poison at 4 mg/kg per day, and it is not a substitute for pain control, dental care or a proper diagnosis. Treat it as a narrow, monitored trial with a stop rule, not a supplement you add and forget.

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