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PetDosageChart

Zyrtec (Cetirizine) Dosage for Dogs

Antihistamine (second-generation) ⏱ Onset: 1-2 hours ⏳ Duration: 24 hours

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator

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Zyrtec Dosage Chart for Dogs by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
5 lbs (2.3 kg) 1mg 2.5mg 2.5mg once daily
10 lbs (4.5 kg) 2.5mg 4.5mg (5mg tablet) 4.5mg (5mg tablet) once daily
15 lbs (6.8 kg) 3.5mg 7mg 7mg once daily
20 lbs (9.1 kg) 4.5mg (5mg tablet) 9mg (2 × 5mg) 9mg (2 × 5mg) once daily
25 lbs (11.3 kg) 5.5mg (5mg tablet) 11.5mg 11.5mg once daily
30 lbs (13.6 kg) 7mg 13.5mg 13.5mg once daily
40 lbs (18.1 kg) 9mg (2 × 5mg) 18mg 18mg once daily
50 lbs (22.7 kg) 11.5mg 22.5mg 22.5mg once daily
60 lbs (27.2 kg) 13.5mg 27mg 27mg once daily
70 lbs (31.7 kg) 16mg (3 × 5mg) 31.5mg 31.5mg once daily
80 lbs (36.3 kg) 18mg 36.5mg 36.5mg once daily
90 lbs (40.8 kg) 20.5mg (4 × 5mg) 41mg (8 × 5mg) 41mg (8 × 5mg) once daily
100 lbs (45.4 kg) 22.5mg 45.5mg (9 × 5mg) 45.5mg (9 × 5mg) once daily
120 lbs (54.4 kg) 27mg 54.5mg (11 × 5mg) 54.5mg (11 × 5mg) once daily
150 lbs (68 kg) 34mg (7 × 5mg) 68mg 68mg once daily

What is Zyrtec (Cetirizine) used for in dogs?

allergies atopic dermatitis itching hives

How to give Zyrtec to your dog

Use plain cetirizine (Zyrtec) only. Do NOT use Zyrtec-D, which contains pseudoephedrine — this decongestant is toxic to dogs. Can be given with or without food. Zyrtec is typically given once daily due to its 24-hour duration of action.

Available Forms

tablet, liquid

Give with Food?

No — can be given without food

Side effects of Zyrtec in dogs

Common side effects

mild sedation
drooling
vomiting

Serious side effects

  • excessive sedation
  • urinary retention
  • hypersensitivity reaction

When to call the vet

Call your vet immediately if your dog shows any of these signs:

  • Signs of allergic reaction worsening
  • Excessive drowsiness
  • Difficulty urinating
  • Vomiting or diarrhea persists
  • Swelling of face or throat

Related Medications for Dogs

Antihistamine (second-generation)

Claritin

Loratadine

For allergies

View dosage chart
Antihistamine (first-generation)

Atarax

Hydroxyzine

For allergies

View dosage chart
First-generation antihistamine

Chlor-Trimeton

Chlorpheniramine

For Allergies

View dosage chart
Antihistamine

Benadryl

Diphenhydramine

For allergies

View dosage chart

Sources & References

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Cetirizine.

Frequently Asked Questions

How much Zyrtec can I give my dog?
The standard dose of Zyrtec (cetirizine) for dogs is 1 mg per kilogram of body weight, given once daily. For example, a 10 kg (22 lb) dog would receive one 10 mg tablet per day. Smaller dogs under 5 kg may receive a half tablet of the 5 mg size.
Can I give my dog Zyrtec every day?
Yes, Zyrtec is commonly given daily for ongoing allergy management in dogs. Its once-daily dosing makes it convenient for long-term use. However, consult your veterinarian before starting any long-term medication to rule out underlying conditions that may need different treatment.
Is Zyrtec safe for dogs?
Plain Zyrtec (cetirizine) is generally considered safe for dogs at the recommended dose. However, you must never use Zyrtec-D, which contains pseudoephedrine — a decongestant that is toxic to dogs and can cause life-threatening symptoms including high blood pressure, seizures, and death.
Can I give my dog Zyrtec and Benadryl together?
It is generally not recommended to give both Zyrtec and Benadryl at the same time without veterinary guidance, as both are antihistamines and combining them increases the risk of excessive sedation and other side effects. Your vet may recommend switching between them or using one at a time.
How long does it take for Zyrtec to work in dogs?
Zyrtec typically begins working within 1-2 hours of administration in dogs. Full effects may take a few days of consistent daily dosing to become apparent, especially for chronic allergy symptoms like atopic dermatitis.

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