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PetDosageChart

Selective serotonin reuptake inhibitor (SSRI) · For Cats

How much Prozac (Fluoxetine) can I give my cat?

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

Onset
4-8 weeks for full behavioral effect
Duration
24 hours per dose
Class
Selective serotonin reuptake inhibitor (SSRI)

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

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By Weight

Prozac 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.

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Dosage Chart · 02

Prozac 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 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 once daily
10 lbs (4.5 kg) 2.5mg 3.5mg 4.5mg once daily
12 lbs (5.4 kg) 2.5mg 4mg 5.5mg once daily
14 lbs (6.3 kg) 3mg 4.5mg 6.5mg once daily
16 lbs (7.3 kg) 3.5mg 5.5mg 7.5mg (10mg tablet) once daily
18 lbs (8.2 kg) 4mg 6mg 8mg (10mg tablet) once daily
20 lbs (9.1 kg) 4.5mg 7mg 9mg (10mg tablet) once daily
25 lbs (11.3 kg) 5.5mg 8.5mg (10mg tablet) 11.5mg (10mg tablet) once daily

Common Uses · 03

What is Prozac (Fluoxetine) used for in cats?

urine spraying inappropriate urination anxiety compulsive overgrooming inter-cat aggression

Administration · 04

How to give Prozac to your cat

Fluoxetine tablets are small and can be given directly or hidden in a pill pocket or small amount of wet food. A typical cat dose is 2.5-5 mg (quarter to half of a 10 mg tablet). Give at the same time each day for consistent blood levels. Do not abruptly stop — taper off gradually under veterinary guidance. Behavioral improvement takes 4-8 weeks, so do not discontinue early thinking it is not working.

Available Forms

tablet, capsule, liquid

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Prozac in cats

Common side effects

decreased appetite
sedation
urinary retention
mild GI upset

Serious side effects — call your vet

  • serotonin syndrome (tremors, agitation, rapid heart rate)
  • severe appetite loss
  • liver toxicity
  • seizures

Emergency · 06

When to call the vet

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

  • Tremors, twitching, or agitation (serotonin syndrome)
  • Complete refusal to eat for more than 48 hours
  • Yellowing of gums or skin (liver toxicity)
  • Seizures or sudden collapse
  • Worsening behavioral issues or new aggression

For Dogs

Looking for Prozac dosage for dogs?

View the Prozac 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 Fluoxetine.

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 once daily. 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

Does Prozac really work for cat spraying?
Yes, fluoxetine is one of the most effective medications for reducing urine spraying in cats, with studies showing a 90%+ reduction in spraying frequency in many cats. However, it should be combined with behavioral modification and environmental enrichment. It works by reducing anxiety and stress-related marking behavior.
How long does fluoxetine take to work in cats?
Fluoxetine typically takes 4-8 weeks to reach full effect in cats. Some improvement may be seen in 2-3 weeks, but do not judge effectiveness until at least 6-8 weeks of consistent daily dosing. If discontinued too early, the problem behavior often returns.
Can my cat take fluoxetine long term?
Yes, many cats take fluoxetine for months to years, sometimes for life. It is generally well tolerated long-term. Your vet may recommend periodic blood work to monitor liver function. Some cats can eventually be weaned off if the underlying behavioral triggers are resolved.
What happens if I suddenly stop giving my cat fluoxetine?
Abruptly stopping fluoxetine can cause withdrawal symptoms including irritability, GI upset, and a return of the original behavioral problem. Always taper the dose gradually over 2-4 weeks under veterinary guidance when discontinuing.
Can I use human fluoxetine for my cat?
Human fluoxetine tablets can be used for cats with veterinary guidance, but the dose must be carefully adjusted — cats typically need only 2.5-5 mg daily (a quarter to half of the smallest human 10 mg tablet). Never give a full human dose. Your vet or a compounding pharmacy can provide an appropriate formulation.

Safety · 10

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