Last updated: June 19, 2026
Cephalexin Dosage Calculator for Cats
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The Cephalexin Dosage Calculator for Cats estimates the antibiotic dose as Dose per administration (mg) = body weight (kg) × prescribed rate (mg/kg), where the typical feline rate is 15–25 mg/kg every 8–12 hours. For a 125 mg/5 mL suspension (25 mg/mL), the liquid volume is the dose in mg divided by 25. For example, a 4 kg cat at 15 mg/kg needs 60 mg (2.4 mL) per dose, twice daily. Cephalexin is a prescription medication, so this tool is an educational dosing aid only — the exact dose, frequency, and duration must be set by a veterinarian.
A cat's cephalexin dose equals its weight in kilograms times the prescribed rate in milligrams per kilogram, typically 15 to 25 milligrams per kilogram every 8 to 12 hours. For example, a 4 kilogram cat at 15 milligrams per kilogram needs about 60 milligrams per dose. Always confirm the dose with your veterinarian.
Key Takeaways
- Dose per administration (mg) = cat weight (kg) × prescribed rate (mg/kg) — a 4 kg cat at 15 mg/kg gets 60 mg
- The typical feline rate is 15–25 mg/kg every 8–12 hours, set by your veterinarian for the specific infection
- Liquid (125 mg/5 mL = 25 mg/mL): mL per dose = dose in mg ÷ 25 — 60 mg equals 2.4 mL
- Weigh in pounds? Divide by 2.2046 to convert to kilograms before dosing
- Always finish the full 7–14 day course to prevent relapse and antibiotic resistance
- Cephalexin is prescription-only — this calculator is a dosing aid, not a substitute for veterinary advice
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
Dose per administration (mg) = Cat weight (kg) × Dosage rate (mg/kg)
Where:
- D_mg=Dose per administration(mg)
- W_kg=Cat body weight(kg)
- R_mg/kg=Dosage rate (typically 15–25 mg/kg)(mg/kg)
Worked Examples
4 kg cat, 15 mg/kg, twice daily
A typical adult cat with a routine skin or urinary infection at the standard 15 mg/kg rate.
- 1Dose = 4 kg × 15 mg/kg = 60 mg per administration
- 2Daily total = 60 mg × 2 doses = 120 mg/day
- 3Liquid (125 mg/5 mL = 25 mg/mL) = 60 ÷ 25 = 2.4 mL per dose
10 lb cat, 20 mg/kg, twice daily
A cat weighed in pounds, prescribed a higher 20 mg/kg rate for a more stubborn infection.
- 1Convert weight: 10 lbs ÷ 2.2046 = 4.54 kg
- 2Dose = 4.54 kg × 20 mg/kg = 90.7 mg per administration
- 3Liquid = 90.7 ÷ 25 = 3.6 mL per dose
5 kg cat, 20 mg/kg, three times daily
A larger cat on an every-8-hour (three times daily) schedule for a severe or deep-tissue infection.
- 1Dose = 5 kg × 20 mg/kg = 100 mg per administration
- 2Daily total = 100 mg × 3 doses = 300 mg/day
- 3Liquid = 100 ÷ 25 = 4.0 mL per dose
Introduction
The Cephalexin Dosage Calculator for Cats estimates the antibiotic dose from your cat's weight and your veterinarian's prescribed rate, then converts it into a liquid volume or capsule count. Cephalexin (cefalexin) is a first-generation cephalosporin used in cats for skin and wound infections, urinary tract infections, and bone infections. The dose per administration is simply weight (kg) × rate (mg/kg), with a typical rate of 15–25 mg/kg every 8–12 hours. This tool is an educational dosing aid, not veterinary advice — cephalexin is a prescription medication, and only your veterinarian can diagnose your cat and set the correct dose, route, and duration. For related tools, see our cat age calculator and cat Benadryl dosage calculator.
Important Safety Information
Antibiotic dosing in cats is a medical decision. Cats are uniquely sensitive to many medications, and an incorrect dose or an inappropriate drug can cause harm. Please read this before using the numbers from this calculator.
- Prescription only:
cephalexin requires a veterinary prescription — never start, stop, or change an antibiotic without your vet
- Confirm the diagnosis:
antibiotics only help bacterial infections; they do nothing for viral illness and can cause harm if misused
- Use your vet's exact rate:
the 15–25 mg/kg range is a guideline — your vet sets the rate for your cat's specific condition
Never use human leftovers or another pet's medication: formulation, strength, and suitability differ
- Finish the full course:
stopping early drives antibiotic resistance and relapse
- Seek urgent care for any allergic reaction:
facial swelling, hives, or difficulty breathing are emergencies
This calculator does not replace professional veterinary judgement. Always confirm every dose with your veterinarian before giving it to your cat.
Cephalexin Dosage Chart for Cats
Use this reference chart for the common starting rate of 15 mg/kg, consistent with veterinary pharmacology references. Your vet may prescribe a different rate (up to ~25 mg/kg) depending on the infection.
| Cat Weight (kg) | Cat Weight (lbs) | Dose at 15 mg/kg (mg) | Liquid 125 mg/5 mL (mL) | Capsule 250 mg |
|---|---|---|---|---|
| 2 | 4.4 | 30 | 1.2 | 0.12 |
| 3 | 6.6 | 45 | 1.8 | 0.18 |
| 4 | 8.8 | 60 | 2.4 | 0.24 |
| 5 | 11.0 | 75 | 3.0 | 0.30 |
| 6 | 13.2 | 90 | 3.6 | 0.36 |
| 7 | 15.4 | 105 | 4.2 | 0.42 |
| 8 | 17.6 | 120 | 4.8 | 0.48 |
How Cephalexin Dosing Works
Cephalexin is a bactericidal antibiotic that kills bacteria by blocking cell-wall synthesis. According to the Merck Veterinary Manual, the typical feline dose is 15–25 mg/kg every 8–12 hours. The calculator multiplies the cat's weight by the prescribed rate and then converts the milligram dose into practical dose forms.
Dose per administration (mg) = weight (kg) × rate (mg/kg)
- Standard rate:
15 mg/kg twice daily (every 12 h) for skin and urinary infections
- Higher rate:
up to 20–25 mg/kg, and/or every 8 h, for more severe infections
- Liquid suspension:
125 mg per 5 mL = 25 mg/mL, so mL per dose = dose (mg) ÷ 25
- Capsules:
commonly 250 mg, so capsules per dose = dose (mg) ÷ 250 (compounding is often needed for cats)
- Course length:
typically 7–14 days — always complete the full course
How to Give Cephalexin to Your Cat
Cephalexin is bitter, and many cats resist it, so technique matters. Consistent timing keeps blood levels steady and the antibiotic effective.
Give with or just after food to reduce stomach upset
Space doses evenly — every 12 hours for twice daily, every 8 hours for three times daily
For liquid, shake the bottle well and measure with the supplied oral syringe, not a kitchen spoon
Ask your vet about a flavoured compounded suspension if your cat refuses the medication
Always provide access to fresh water
Wash your hands after handling the medication
Set phone alarms for each dose. Even spacing (e.g. 8 am / 8 pm) keeps drug levels in the effective range and improves the chance of clearing the infection.
What to Do About a Missed Dose
Missing an occasional dose is common. Handle it safely rather than doubling up.
Give the missed dose as soon as you remember
If it is almost time for the next dose, skip the missed one and resume the normal schedule
Never give two doses at once or 'catch up' — doubling can cause vomiting and other side effects
If your cat spits out or vomits a dose, do not automatically re-dose — call your vet for advice
Keep a simple dosing log so you do not lose track over a 1–2 week course
When Cephalexin Is Prescribed for Cats
Cephalexin is effective against many gram-positive bacteria and some gram-negative organisms that commonly infect cats.
Skin infections (pyoderma): often Staphylococcus species
Wound and bite-abscess infections, including post-surgical sites
Urinary tract infections caused by susceptible bacteria
Bone infections (osteomyelitis): cephalexin penetrates bone well
Some soft-tissue and ear infections, at the vet's discretion
Side Effects, Cautions, and When to Call the Vet
Cephalexin is generally well tolerated in cats, but watch for adverse effects and know when a reaction is an emergency.
- Common (mild):
vomiting, diarrhoea, or reduced appetite — giving with food usually helps
- Allergy/penicillin cross-reactivity:
avoid in cats with a known cephalosporin or penicillin allergy
- Kidney disease:
cephalexin is cleared by the kidneys, so impaired cats may need dose adjustment and monitoring
- Pregnancy/nursing and very young kittens:
use only under direct veterinary supervision
- Drug interactions:
tell your vet about every other medication and supplement your cat receives
Call your veterinarian immediately for facial swelling, hives, difficulty breathing, persistent vomiting, lethargy, or yellowing of the gums or eyes — these can signal a serious reaction.
Storage and Handling
Correct storage keeps the medication safe and effective for the full course.
Liquid (reconstituted) suspension: refrigerate and discard after the period stated on the label (often ~14 days)
Capsules/tablets: store at room temperature, away from moisture and direct light
Keep all medications out of reach of pets and children
Do not use past the expiry date or if the suspension looks or smells abnormal
Dispose of unused antibiotics via a pharmacy take-back program, not down the drain
Glossary of Dosing Terms
Key terms that appear in feline antibiotic prescriptions and in this calculator:
| Term | Meaning |
|---|---|
| mg/kg | Milligrams of drug per kilogram of body weight — the prescribed dosing rate. |
| Dose per administration | The amount given at one time (weight × rate). |
| Daily dose | The total over 24 hours = dose per administration × number of doses per day. |
| q12h / q8h | Veterinary shorthand for 'every 12 hours' / 'every 8 hours'. |
| BID / TID | Twice daily / three times daily. |
| Suspension | A liquid form of the drug; cephalexin is commonly 125 mg per 5 mL (25 mg/mL). |
| Bactericidal | Kills bacteria (as opposed to merely stopping their growth). |
| Compounding | A pharmacy custom-preparing a flavoured or cat-sized formulation. |
Quick Reference Card
Cephalexin for Cats — Quick Reference
Quick reference • Cephalexin Dosage Calculator for Cats
Dose (mg) = Weight (kg) × Rate (mg/kg) • Liquid (mL) = Dose ÷ 25 • Daily = Dose × doses/dayValid range: Typical rate 15–25 mg/kg every 8–12 h; vet-prescribed
Common Values
⚠ Watch Out
- •Prescription medication — always confirm the dose, frequency, and duration with your veterinarian
- •Never use a dog's or a person's cephalexin, or any leftover antibiotic
- •Finish the entire course; stopping early drives resistance and relapse
- •Stop and call your vet for facial swelling, hives, breathing trouble, or persistent vomiting
Pro Tips
- →Give with food and at evenly spaced times (e.g. every 12 h) to improve tolerance and efficacy
- →Measure liquid with the supplied oral syringe, never a kitchen spoon
- →Set alarms and keep a dosing log over the 1–2 week course
- →Ask your vet about a flavoured compounded suspension if your cat refuses the medication
FAQs
What is cephalexin used for in cats?
Cephalexin is an antibiotic used to treat bacterial infections in cats, including skin infections (pyoderma), urinary tract infections, wound and abscess infections, and bone infections. It is effective against Staphylococcus, Streptococcus, and some other bacteria, but only works against bacterial — not viral — illness.
What is the correct cephalexin dose for cats?
The typical veterinary dose is 15–25 mg/kg of body weight every 8–12 hours. For example, a 4 kg cat at 15 mg/kg receives 60 mg per dose. The exact rate, frequency, and duration must be set by your veterinarian for your cat's specific infection — this calculator only estimates the amount for a rate your vet provides.
How do I calculate my cat's cephalexin dose?
Multiply your cat's weight in kilograms by the prescribed rate in mg/kg: Dose = Weight (kg) × Rate (mg/kg). If you weigh your cat in pounds, divide by 2.2046 to get kilograms first. To convert to liquid, divide the milligram dose by 25 (for a 125 mg/5 mL suspension). This calculator does all of this automatically.
How much liquid cephalexin should I give my cat?
The common suspension is 125 mg per 5 mL, which is 25 mg/mL. Divide the prescribed milligram dose by 25 to get the volume in mL. A 60 mg dose, for example, is 60 ÷ 25 = 2.4 mL. Always measure with the oral syringe provided, not a kitchen spoon.
How long should cats take cephalexin?
Treatment usually lasts 7–14 days, but the exact length is set by your vet based on the infection. Always finish the entire course even if your cat seems better — stopping early can let the infection return and promote antibiotic-resistant bacteria.
Can cephalexin cause side effects in cats?
The most common side effects are mild: vomiting, diarrhoea, or reduced appetite, especially on an empty stomach — giving the dose with food usually helps. Serious allergic reactions (facial swelling, hives, difficulty breathing) are rare but are emergencies that need immediate veterinary care.
What if I miss a dose?
Give the missed dose as soon as you remember. If it is nearly time for the next one, skip the missed dose and continue the normal schedule. Never give two doses at once to catch up, as this increases the risk of side effects.
Can I give my cat cephalexin prescribed for a dog or a person?
No. Never use another animal's or a person's medication. The strength, formulation, and suitability differ, and some human products contain ingredients unsafe for cats. Only give cephalexin that your veterinarian has prescribed specifically for your cat.
Should cephalexin be given with food?
Yes, giving cephalexin with or just after food helps reduce stomach upset such as vomiting or loss of appetite. It can be given without food, but most cats tolerate it better with a small meal.