Zyrtec (Cetirizine) Dosage Calculator for Dogs by Weight
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 — sold as Zyrtec — is a second-generation antihistamine that causes less drowsiness than Benadryl. Veterinarians use it for seasonal allergies and itching in dogs. Published references (including the AAHA allergic skin disease guidelines table) list 1–2 mg per kg once daily; this calculator uses the conservative 1 mg/kg end.
Many veterinarians in practice keep the daily dose around 10 mg for large dogs unless they direct otherwise. Enter your dog's weight below, convert to standard 10 mg tablets, and read the critical Zyrtec-D warning before giving anything.
Dose calculator
Dosage chart by weight
| Dog weight | Dose range per dose |
|---|---|
| 5 lb | 2.3 mg |
| 10 lb | 4.5 mg |
| 15 lb | 6.8 mg |
| 20 lb | 9.1 mg |
| 30 lb | 13.5 mg |
| 40 lb | 18 mg |
| 50 lb | 22.5 mg |
| 60 lb | 27 mg |
| 80 lb | 36.5 mg |
| 100 lb | 45.5 mg |
Chart uses the same conservative range as the calculator (1 mg per kg of body weight (conservative end of the published 1–2 mg/kg range)). Always confirm with your veterinarian.
Common formulations
- Tablets — 10 mg tablets
Standard Zyrtec tablet - 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). 1 mg per kg of body weight (conservative end of the published 1–2 mg/kg range).
In practice, many veterinarians keep the daily dose at about 10 mg for large dogs unless they direct otherwise.
Common veterinary uses
- Seasonal allergies and itching
- Sneezing / runny nose from allergies
- Mild allergic skin flare-ups
Safety warnings
Possible side effects
- Mild drowsiness (less than with Benadryl)
- Vomiting
- Drooling / excessive thirst
- Rarely: agitation
- CRITICAL: never use Zyrtec-D — it contains pseudoephedrine, which is toxic to dogs and can cause dangerous heart effects.
- Use plain cetirizine only — check that it is the sole active ingredient.
- Check liquid inactive ingredients for xylitol.
Do not use (or ask your vet first)
- Dogs with kidney disease need vet-adjusted dosing
- Pregnant or nursing dogs — ask your vet first
When to see a veterinarian
- Vomiting, extreme lethargy, or loss of appetite after dosing
- Rapid heart rate or agitation (possible wrong-product ingestion — emergency)
- Allergy symptoms do not improve within several days
- Your dog takes other medications — check for interactions first
Frequently asked questions
How much Zyrtec can I give my dog?
The conservative published reference is 1 mg/kg once daily — for example, a 20 kg (44 lb) dog would be about 20 mg, though many vets in practice use around 10 mg daily for large dogs. Confirm with your vet.
Can I give my dog Zyrtec every day?
Veterinarians do use it daily through allergy seasons. Ongoing daily use should be vet-directed so the underlying allergy is properly managed.
Is Zyrtec or Benadryl better for dogs?
Cetirizine (Zyrtec) typically causes less drowsiness and is dosed once daily, which many owners prefer. Benadryl has a longer track record for acute reactions. Your vet can advise which fits your dog.
What happens if my dog ate Zyrtec-D?
Zyrtec-D contains pseudoephedrine, which is dangerous for dogs — restlessness, rapid heart rate, vomiting, or tremors can occur. Contact your vet or poison control immediately; this is an emergency.
How fast does Zyrtec work in dogs?
Usually within 1–2 hours, with effects lasting about 24 hours — which is why it is dosed once daily.
Sources
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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.