Selective serotonin reuptake inhibitor (SSRI) · For Cats

Prozac dosage reference for cats (Fluoxetine)

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

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.

Fluoxetine (often known by brand names such as Prozac and Reconcile) is a selective serotonin reuptake inhibitor (SSRI) commonly used in veterinary medicine for urine spraying, inappropriate urination, anxiety, compulsive overgrooming, and inter-cat aggression. Understanding the correct dosage, administration, and potential side effects of Fluoxetine is critical for your cat’s safety and well-being.

A typical Fluoxetine 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, capsule, and liquid.

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.

Fluoxetine Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Fluoxetine 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 Fluoxetine amounts for common cat weights, for quick reference:

Dosage Chart · 02

Prozac 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	once daily
10 lbs (4.5 kg)	2.3 mg	3.4 mg	4.5 mg	once daily
12 lbs (5.4 kg)	2.7 mg	4.1 mg	5.4 mg	once daily
14 lbs (6.3 kg)	3.1 mg	4.7 mg	6.3 mg	once daily
16 lbs (7.3 kg)	3.6 mg	5.5 mg	7.3 mg	once daily
18 lbs (8.2 kg)	4.1 mg	6.1 mg	8.2 mg (10mg tablet)	once daily
20 lbs (9.1 kg)	4.5 mg	6.8 mg	9.1 mg (10mg tablet)	once daily
25 lbs (11.3 kg)	5.7 mg	8.5 mg (10mg tablet)	11.3 mg (10mg tablet)	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

Prozac 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 Fluoxetine 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.

It is generally recommended to give Fluoxetine with food to help reduce stomach upset. It may interact with MAO inhibitors, tramadol, mirtazapine, buspirone, and trazodone.

Side Effects and Safety

Common side effects include decreased appetite, sedation, urinary retention, and mild GI upset. More serious side effects can occur, such as serotonin syndrome (tremors, agitation, rapid heart rate), severe appetite loss, liver toxicity, and seizures.

Cautions · 12

When Prozac should be used with caution or avoided

Some cats should not take Prozac, 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 Prozac.

concurrent use with MAO inhibitors
severe liver disease
seizure disorders
pregnancy

Interactions · 13

Prozac drug interactions

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

MAO inhibitors

tramadol

mirtazapine

buspirone

trazodone

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 Prozac, 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:

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

Frequently Asked Questions

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.

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 Prozac. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: urine spraying, inappropriate urination, anxiety, compulsive overgrooming, inter-cat aggression
Recorded forms: tablet, capsule, liquid
Reference timing: once daily; onset 4-8 weeks for full behavioral effect; duration 24 hours per dose

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

concurrent use with MAO inhibitors; severe liver disease; seizure disorders; pregnancy.

Recorded interactions

MAO inhibitors; tramadol; mirtazapine; buspirone; trazodone.

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.

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.

Plumb's Veterinary Drug Handbook — listed in this medication's source record.
Merck Veterinary Manual — listed in this medication's source record.
DailyMed label search for Fluoxetine — check current product and formulation labels; some veterinary uses may be off-label.

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

Pet Medication Safety Hub — What's safe, what's dangerous, and emergency signs
How we calculate dosages — Our sources, math, and review process
Printable emergency checklist — One-page reference for your fridge or first aid kit