Zyrtec (Cetirizine) Dosage Calculator for Cats
Dose ranges on this page are published veterinary references for education only. Your veterinarian's prescribed dose always wins. When in doubt, call your vet first.
Cetirizine (Zyrtec) is occasionally used in cats for allergies and itching. Veterinary dosing charts list a conservative feline range of about 2.5–5 mg per cat, given once daily — for most cats, that means half of a 5 mg tablet.
Because cat doses are small and kidney disease changes how the drug is cleared, check with your veterinarian before giving cetirizine to your cat.
Dose calculator
Dosage chart by weight
| Cat weight | Dose range per dose |
|---|---|
| 5 lb | 2.5–5 mg (per cat) |
| 8 lb | 2.5–5 mg (per cat) |
| 10 lb | 2.5–5 mg (per cat) |
| 12 lb | 2.5–5 mg (per cat) |
| 15 lb | 2.5–5 mg (per cat) |
| 18 lb | 2.5–5 mg (per cat) |
| 20 lb | 2.5–5 mg (per cat) |
Chart uses the same conservative range as the calculator (2.5–5 mg per cat (conservative feline range)). Always confirm with your veterinarian.
Common formulations
- Tablets — 5 mg tablets
5 mg tablets exist; 10 mg tablets must be split into quarters - Liquid syrup (5 mg / 5 mL) — 5 mg / 5 mL
Check inactive ingredients — no xylitol
Use the calculator above to convert any of these sizes into an amount for your pet's weight.
How often to give it
Once daily (every 24 hours). 2.5–5 mg per cat (conservative feline range).
Common veterinary uses
- Mild allergies and itching (vet-directed)
- Sneezing from allergies (vet-directed)
Safety warnings
Possible side effects
- Mild drowsiness
- Vomiting
- Drooling
- CRITICAL: never use Zyrtec-D — pseudoephedrine is toxic to cats.
- Use plain cetirizine only — confirm it is the sole active ingredient.
- Check liquid inactive ingredients for xylitol.
Do not use (or ask your vet first)
- Cats with kidney disease need vet-adjusted dosing
- Pregnant or nursing cats — ask your vet first
When to see a veterinarian
- Vomiting, extreme lethargy, or appetite loss after dosing
- Rapid heart rate or agitation (possible wrong-product ingestion — emergency)
- Symptoms do not improve within several days
- Your cat has kidney disease — dosing must be vet-directed
Frequently asked questions
Can cats take Zyrtec?
It is occasionally used in cats under veterinary direction. Published charts list about 2.5–5 mg per cat once daily — roughly half of a 5 mg tablet for an average cat. Confirm with your vet first.
How do I split a Zyrtec tablet for my cat?
5 mg tablets can be halved; 10 mg tablets must be quartered for a ~2.5 mg dose. A pill splitter helps accuracy — or ask your vet about liquid formulations.
How much Zyrtec for a 10 lb cat?
Feline dosing is per-cat rather than strictly by weight: the conservative published range is 2.5–5 mg once daily regardless of typical adult cat weight. Confirm with your vet.
Is Zyrtec-D safe for cats?
No — never. Zyrtec-D contains pseudoephedrine, which is toxic to cats. Use plain cetirizine only.
Sources
- Cedarview Veterinary Clinic — Antihistamine Dosing Chart (PDF)
- Fi Blog — Can Dogs Take Zyrtec? (background)
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Dose ranges on this page are published veterinary references for education only. Your veterinarian's prescribed dose always wins. When in doubt, call your vet first.