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PetDosageChart

Zyrtec (Cetirizine) Dosage for Cats

Second-Generation Antihistamine (H1 Receptor Antagonist) ⏱ 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 Cats by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
3 lbs (1.4 kg) 0.5mg 1mg 1.5mg Once daily
4 lbs (1.8 kg) 1mg 1.5mg 2mg Once daily
5 lbs (2.3 kg) 1mg 1.5mg 2.5mg Once daily
6 lbs (2.7 kg) 1.5mg 2mg 2.5mg Once daily
7 lbs (3.2 kg) 1.5mg 2.5mg 3mg Once daily
8 lbs (3.6 kg) 2mg 2.5mg 3.5mg Once daily
9 lbs (4.1 kg) 2mg 3mg 4mg (5mg tablet) Once daily
10 lbs (4.5 kg) 2.5mg 3.5mg 4.5mg (5mg tablet) Once daily
12 lbs (5.4 kg) 2.5mg 4mg (5mg tablet) 5.5mg (5mg tablet) Once daily
14 lbs (6.3 kg) 3mg 4.5mg (5mg tablet) 6.5mg Once daily
16 lbs (7.3 kg) 3.5mg 5.5mg (5mg tablet) 7.5mg Once daily
18 lbs (8.2 kg) 4mg (5mg tablet) 6mg (5mg tablet) 8mg Once daily
20 lbs (9.1 kg) 4.5mg (5mg tablet) 7mg 9mg (2 × 5mg) Once daily
25 lbs (11.3 kg) 5.5mg (5mg tablet) 8.5mg 11.5mg Once daily

What is Zyrtec (Cetirizine) used for in cats?

Allergic dermatitis and itching Environmental allergies (atopy) Feline eosinophilic granuloma complex (adjunctive) Allergic rhinitis and sneezing

How to give Zyrtec to your cat

Cetirizine tablets can be cut to size and hidden in a pill pocket or soft treat. For a 5 mg dose, use a half of a 10 mg tablet. For more precise dosing, use the children's liquid cetirizine (1 mg/mL) measured with an oral syringe—this is often the easiest method for cats. The liquid can be squirted directly into the mouth or mixed with a small amount of wet food. Can be given with or without food. Always verify the product is plain cetirizine—NEVER Zyrtec-D (with pseudoephedrine).

Available Forms

Tablet, Oral liquid/syrup

Give with Food?

No — can be given without food

Side effects of Zyrtec in cats

Common side effects

Mild sedation
Drooling (if tablet is chewed)
Decreased appetite
Vomiting (uncommon)

Serious side effects

  • Urinary retention
  • Severe sedation
  • Liver toxicity (rare)
  • Paradoxical hyperexcitability

When to call the vet

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

  • Difficulty urinating, straining, or no urine output
  • Excessive sedation or difficulty waking
  • Persistent vomiting or diarrhea
  • Signs of allergic reaction to the medication (facial swelling, difficulty breathing)
  • Behavioral changes such as severe agitation or hiding

Related Medications for Cats

Second-Generation Antihistamine (H1 Receptor Antagonist)

Claritin

Loratadine

For Allergic dermatitis

View dosage chart
Antihistamine (H1 Receptor Antagonist)

Atarax

Hydroxyzine

For Allergic dermatitis and itching

View dosage chart
NK1 receptor antagonist / Antiemetic

Cerenia

Maropitant

For vomiting

View dosage chart
H2 receptor antagonist

Pepcid

Famotidine

For stomach acid reduction

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

Can I give my cat Zyrtec for allergies?
Yes, plain cetirizine (Zyrtec) is commonly recommended by veterinarians for managing allergies in cats. The typical dose is 0.5-1 mg/kg once daily. For most average-sized cats (4-5 kg), this works out to about 2.5-5 mg daily, which is a quarter to a half of a 10 mg tablet. NEVER use Zyrtec-D, which contains pseudoephedrine that is toxic and potentially fatal to cats.
Is Zyrtec or Benadryl better for cats?
Cetirizine (Zyrtec) is often preferred over diphenhydramine (Benadryl) for cats because it only needs to be given once daily (versus every 8-12 hours for Benadryl) and causes less sedation. Both are considered safe for cats when properly dosed. Zyrtec may also be slightly more effective for skin allergies. Discuss with your vet which is best for your cat's specific situation.
How much Zyrtec can I give my cat?
The standard cetirizine dose for cats is 0.5-1 mg/kg once daily. For a typical 4-5 kg cat, give 2.5-5 mg once daily. Most vets recommend starting with a half of a 5 mg tablet (2.5 mg) for an average cat and adjusting as needed. The children's liquid form (1 mg/mL) makes measuring smaller doses much easier and more accurate.
Can Zyrtec help with my cat's itching and overgrooming?
Cetirizine can help reduce itching and subsequent overgrooming in cats with allergic skin conditions. It works by blocking histamine receptors involved in the allergic itch response. However, overgrooming in cats can have many causes beyond allergies (stress, pain, parasites), so it is important to have your vet determine the underlying cause. Antihistamines work best as part of a comprehensive allergy management plan.
Are there side effects of Zyrtec in cats?
Cetirizine is generally well-tolerated in cats with minimal side effects. The most common is mild sedation, which usually decreases over the first few days of use. Some cats may experience decreased appetite or mild GI upset. Serious side effects are rare but can include urinary retention or severe drowsiness. If your cat seems overly sedated, reduce the dose and consult your vet.

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