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.
Dosage Calculator
Enter your cat's weight to calculate the recommended dose.
Recommended Dosage
Low Dose
—
mg
Standard Dose
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mg
Max Dose
—
mg
Frequency
Once daily
💊 Closest Tablet
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These calculations are estimates based on standard veterinary dosing guidelines. Always confirm with your veterinarian before administering medication.
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
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.