Zyrtec for Dogs: Dosage Calculator
Cetirizine (Zyrtec) is a second-generation antihistamine that causes less drowsiness than Benadryl. The commonly published veterinary range for dogs is 0.5–1 mg/kg once a day; some vets split it twice daily.
Enter your dog's weight to see the published reference range. Used for seasonal and environmental allergy itch.
Zyrtec dosage chart for dogs by weight
cetirizine 0.5–1 mg/kg, once daily (sometimes split twice daily by your vet). Tablets rounded to quarters and kept inside the range. Reference only: confirm with your vet.
| Dog weight | mg range | Zyrtec tablet, 10 mg | Zyrtec tablet, 5 mg | Children's Zyrtec liquid, 1 mg / mL |
|---|---|---|---|---|
| 5 lb (2.3 kg) | 1.1–2.3 mg | less than ¼ (ask vet) | 0.25 | 1.1–2.3 mL |
| 10 lb (4.5 kg) | 2.3–4.5 mg | 0.25 | 0.5–0.75 | 2.3–4.5 mL |
| 15 lb (6.8 kg) | 3.4–6.8 mg | 0.5 | 0.75–1.25 | 3.4–6.8 mL |
| 20 lb (9.1 kg) | 4.5–9.1 mg | 0.5–0.75 | 1–1.75 | 4.5–9.1 mL |
| 30 lb (13.6 kg) | 6.8–14 mg | 0.75–1.25 | 1.5–2.5 | 6.8–13.6 mL |
| 40 lb (18.1 kg) | 9.1–18 mg | 1–1.75 | 2–3.5 | 9.1–18.1 mL |
| 50 lb (22.7 kg) | 11–23 mg | 1.25–2.25 | 2.5–4.5 | 11.3–22.7 mL |
| 60 lb (27.2 kg) | 14–27 mg | 1.5–2.5 | 2.75–5.25 | 13.6–27.2 mL |
| 70 lb (31.8 kg) | 16–32 mg | 1.75–3 | 3.25–6.25 | 15.9–31.8 mL |
| 80 lb (36.3 kg) | 18–36 mg | 2–3.5 | 3.75–7.25 | 18.1–36.3 mL |
| 100 lb (45.4 kg) | 23–45 mg | 2.5–4.5 | 4.75–9 | 22.7–45.4 mL |
For large dogs, vets often stay at the low end of the range or cap a single dose. Your highlighted row follows the weight you entered above.
How "mg per kg" dosing works
It only helps some allergic dogs, so ask your vet whether it suits yours and at what dose.
Vets dose by body weight because the same amount of drug is spread through a bigger or smaller body. Drag the weight to see how the reference range and the number of tablets move together, and why a tablet sized for a 70 kg adult human can be a big dose for a small pet.
Range 6.8–13.6 mg = 0.75–1.25 tablets of Zyrtec tablet, 10 mg. For comparison, a typical adult human dose is based on about 70 kg.
Warnings before giving Zyrtec
- Never give Zyrtec-D. Pseudoephedrine is highly toxic to dogs.
- Check children's liquids and dissolving tablets for xylitol.
- Side effects are uncommon but can include mild sleepiness, vomiting or drooling.
- Dogs with kidney or liver disease may need a lower dose; ask your vet.
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Questions owners ask
How much Zyrtec can I give my dog?
The usual veterinary reference range is 0.5–1 mg/kg once daily. A 45 lb (20 kg) dog comes to 10–20 mg, so one 10 mg tablet sits at the low end. Your vet sets the final dose.
Is Zyrtec or Benadryl better for dogs?
Cetirizine usually causes less drowsiness and is given once a day, while diphenhydramine is shorter-acting. Neither works for every dog; vets often try one for 1–2 weeks and judge the response.
How long does Zyrtec take to work in dogs?
It is absorbed within a couple of hours, but judging whether it controls allergy itch usually takes 1–2 weeks of regular dosing.