Skip to main content
PetDosageChart

Serotonin (5-HT3) antagonist antiemetic · For Cats

How much Zofran (Ondansetron) can I give my cat?

Standard Zofran dose for cats is 0.75 mg per kg (0.34 mg per lb), given every 8-12 hours. Use the calculator below for your cat's exact weight, or jump to the weight-by-weight chart.

Onset
30-60 minutes (oral), 10-15 minutes (injectable)
Duration
8-12 hours
Class
Serotonin (5-HT3) antagonist antiemetic

Calculator estimate from Plumb’s Veterinary Drug Handbook. Not yet vet-reviewed — see our methodology .

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. Sourced from Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator · 01

Enter your cat's weight

By Weight

Zofran dose by cat weight

Pick your cat's weight to jump to a dedicated page with the dose, frequency, safety notes, and FAQ for that size.

Embed this calculator on your site

Get a free Zofran dosage widget

Get embed code

Free forever. Works in any blog post or article. Adds a small "Powered by petdosagechart.com" credit at the bottom.

Dosage Chart · 02

Zofran dosage for cats by weight

Scroll sideways to see full table

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

Common Uses · 03

What is Zofran (Ondansetron) used for in cats?

nausea vomiting chemotherapy-induced nausea post-anesthetic nausea motion sickness

Administration · 04

How to give Zofran to your cat

Ondansetron can be given with or without food. For cats, a typical dose is 0.5-1 mg/kg, which usually means a quarter to half of a 4 mg tablet for an average cat. The oral dissolving tablet (ODT) can be placed on the tongue where it dissolves quickly — this is helpful for cats that are actively nauseous and may vomit up a regular tablet. For severe vomiting, the injectable form can be given by your vet to bypass the GI tract entirely.

Available Forms

tablet, injectable, oral dissolving tablet

Give with Food?

No — can be given without food

Side Effects · 05

Side effects of Zofran in cats

Common side effects

constipation
mild sedation
headache
mild diarrhea

Serious side effects — call your vet

  • cardiac arrhythmias (QT prolongation)
  • serotonin syndrome with other serotonergic drugs
  • severe constipation
  • hypersensitivity reaction

Emergency · 06

When to call the vet

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

  • Vomiting continues despite ondansetron treatment
  • Signs of dehydration (sunken eyes, dry gums, skin tenting)
  • Blood in vomit or stool
  • Lethargy or inability to keep water down
  • Rapid or irregular heartbeat

For Dogs

Looking for Zofran dosage for dogs?

View the Zofran dosage chart and calculator for dogs.

Related · 08

Related medications for cats

Sources · 09

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 Ondansetron.

Read more about our methodology and how we calculate dosages.

Transparency · 11

How this page was made

Sourced from Plumb's Veterinary Drug Handbook, the reference used in US vet schools. Every dose, frequency, and tablet count on this page is generated from that data, then checked against the published references below.

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 every 8-12 hours. The calculator multiplies that basis by your cat's weight and rounds to the closest available tablet size.
Last-reviewed status
Automated from Plumb’s, not yet vet-reviewed.

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

Frequently Asked · 07

Questions about this medication

Is ondansetron safe for cats?
Yes, ondansetron is considered safe and effective for cats. It is one of the most potent antiemetics available and is widely used in both human and veterinary medicine. It works by blocking serotonin receptors in the vomiting center of the brain and in the GI tract. It has fewer sedating effects than some other antiemetics.
How is ondansetron different from Cerenia for cats?
Both are effective antiemetics but work through different mechanisms. Cerenia (maraviroc) blocks substance P, while ondansetron blocks serotonin (5-HT3) receptors. Cerenia is FDA-approved for dogs but used off-label in cats. Ondansetron may be preferred for chemotherapy-induced nausea and is available in more convenient forms like oral dissolving tablets.
Can I give my cat ondansetron for car sickness?
Yes, ondansetron can help with motion sickness in cats. Give it 30-60 minutes before travel. However, for routine travel nausea, Cerenia (maropitant) may be more effective as it specifically targets motion-induced vomiting pathways. Consult your vet about the best option for your cat.
How much ondansetron can I give my cat?
The typical dose is 0.5-1 mg/kg every 8-12 hours. For an average 4-5 kg cat, this means approximately 2-4 mg per dose. A quarter to half of a 4 mg tablet is a common starting dose. Always follow your veterinarian's specific dosing instructions.
Can ondansetron be used with other medications?
Ondansetron can be safely combined with most medications, but caution is needed with serotonergic drugs (SSRIs like fluoxetine, tramadol) due to serotonin syndrome risk, and with drugs that prolong the QT interval on ECG. Always inform your vet of all medications your cat is taking.

Safety · 10

More resources