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Second-Generation Antihistamine (H1 Receptor Antagonist) · For Cats

Zyrtec dosage reference for cats (Cetirizine)

This page's standard weight-based reference is 0.75 mg per kg (0.34 mg per lb), with Once daily recorded as the reference frequency. Use the calculator to see the arithmetic for your cat's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset
1-2 hours
Duration
24 hours
Class
Second-Generation Antihistamine (H1 Receptor Antagonist)

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Cetirizine (often known by brand names such as Zyrtec) is a second-generation antihistamine (H1 receptor antagonist) commonly used in veterinary medicine for Allergic dermatitis and itching, Environmental allergies (atopy), Feline eosinophilic granuloma complex (adjunctive), and Allergic rhinitis and sneezing. Understanding the correct dosage, administration, and potential side effects of Cetirizine is critical for your cat’s safety and well-being.

A typical Cetirizine dose for cats is around 0.75 mg/kg Once daily, within a usual range of 0.5-1 mg/kg. Available forms include Tablet and Oral liquid/syrup.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

Cetirizine Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Cetirizine dose from the 0.75 mg/kg guideline. Your veterinarian may adjust it for your cat’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your cat's weight

Quick Dosage Chart

Typical Cetirizine amounts for common cat weights, for quick reference:

Dosage Chart · 02

Zyrtec weight-based reference chart for cats

Scroll sideways to see full table

Weight Lower Reference Standard Reference Upper Reference Frequency
3 lbs (1.4 kg) 0.70 mg 1.0 mg 1.4 mg Once daily
4 lbs (1.8 kg) 0.90 mg 1.4 mg 1.8 mg Once daily
5 lbs (2.3 kg) 1.1 mg 1.7 mg 2.3 mg Once daily
6 lbs (2.7 kg) 1.4 mg 2.0 mg 2.7 mg Once daily
7 lbs (3.2 kg) 1.6 mg 2.4 mg 3.2 mg Once daily
8 lbs (3.6 kg) 1.8 mg 2.7 mg 3.6 mg Once daily
9 lbs (4.1 kg) 2.0 mg 3.1 mg 4.1 mg (5mg tablet) Once daily
10 lbs (4.5 kg) 2.3 mg 3.4 mg 4.5 mg (5mg tablet) Once daily
12 lbs (5.4 kg) 2.7 mg 4.1 mg (5mg tablet) 5.4 mg (5mg tablet) Once daily
14 lbs (6.3 kg) 3.1 mg 4.7 mg (5mg tablet) 6.3 mg Once daily
16 lbs (7.3 kg) 3.6 mg 5.5 mg (5mg tablet) 7.3 mg Once daily
18 lbs (8.2 kg) 4.1 mg (5mg tablet) 6.1 mg (5mg tablet) 8.2 mg Once daily
20 lbs (9.1 kg) 4.5 mg (5mg tablet) 6.8 mg 9.1 mg (2 × 5mg) Once daily
25 lbs (11.3 kg) 5.7 mg (5mg tablet) 8.5 mg 11.3 mg Once daily

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Zyrtec reference by cat weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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How to Give Cetirizine 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).

It may interact with CNS depressants (additive sedation), Other antihistamines (additive effects and sedation), Theophylline (may decrease cetirizine clearance), and Anticholinergic drugs (additive drying effects).

Side Effects and Safety

Common side effects include Mild sedation, Drooling (if tablet is chewed), Decreased appetite, and Vomiting (uncommon). More serious side effects can occur, such as Urinary retention, Severe sedation, Liver toxicity (rare), and Paradoxical hyperexcitability.

Cautions · 12

When Zyrtec should be used with caution or avoided

Some cats should not take Zyrtec, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Zyrtec.

  • Known hypersensitivity to cetirizine or hydroxyzine
  • Severe kidney disease (cetirizine is renally excreted)
  • NEVER use Zyrtec-D (contains pseudoephedrine, which is toxic to cats)

Interactions · 13

Zyrtec drug interactions

Zyrtec can interact with other drugs. This list is not complete — always give your veterinarian a full list of your cat's medications and supplements.

CNS depressants (additive sedation)
Other antihistamines (additive effects and sedation)
Theophylline (may decrease cetirizine clearance)
Anticholinergic drugs (additive drying effects)

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult cat at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

  • In an emergency, or after accidental ingestion or a suspected overdose
  • For pregnant or nursing pets
  • For very young or very old cats
  • For pets with liver disease, kidney disease, or another chronic illness
  • For pets taking several medications at once
  • When you are not sure of your cat's current, accurate weight
  • For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your cat had too much Zyrtec, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

  • Call your veterinarian or the nearest emergency animal hospital.
  • ASPCA Animal Poison Control Center: (888) 426-4435
  • Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your cat experiences any of the following, contact your veterinarian or an emergency clinic immediately:

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

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.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your cat's weight by the lower, standard, and upper mg/kg values recorded for Zyrtec. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses
Allergic dermatitis and itching, Environmental allergies (atopy), Feline eosinophilic granuloma complex (adjunctive), Allergic rhinitis and sneezing
Recorded forms
Tablet, Oral liquid/syrup
Reference timing
Once daily; onset 1-2 hours; duration 24 hours

Individual checks a calculator cannot perform

  • Confirm the diagnosis and the reason this medication is being considered.
  • Match the exact product, concentration, route, and whether a tablet may be split.
  • Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
  • Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

Known hypersensitivity to cetirizine or hydroxyzine; Severe kidney disease (cetirizine is renally excreted); NEVER use Zyrtec-D (contains pseudoephedrine, which is toxic to cats).

Recorded interactions

CNS depressants (additive sedation); Other antihistamines (additive effects and sedation); Theophylline (may decrease cetirizine clearance); Anticholinergic drugs (additive drying effects).

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your cat's complete medication list before acting on a number.

For Dogs

Looking for Zyrtec dosage for dogs?

View the Zyrtec dosage chart and calculator for dogs.

Related · 08

Related medications for cats

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

Source names are shown at the record level; passage-level page and label citations are still being added. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 0.75 mg per kg (0.34 mg per lb) of body weight, given Once daily. The calculator multiplies that basis by your cat's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner
Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status
Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review cats dosage data.

Safety · 10

More resources