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First-Generation Cephalosporin Antibiotic · For Cats

How much Cephalexin (Keflex) can I give my cat?

Standard Cephalexin dose for cats is 15 mg per kg (6.80 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
1-2 hours
Duration
8-12 hours per dose
Class
First-Generation Cephalosporin Antibiotic

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

Keflex 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

Keflex dosage for cats by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
3 lbs (1.4 kg) 14mg 21mg 35mg Every 8-12 hours
4 lbs (1.8 kg) 18mg 27mg 45mg Every 8-12 hours
5 lbs (2.3 kg) 23mg 34.5mg 57.5mg Every 8-12 hours
6 lbs (2.7 kg) 27mg 40.5mg 67.5mg Every 8-12 hours
7 lbs (3.2 kg) 32mg 48mg 80mg Every 8-12 hours
8 lbs (3.6 kg) 36mg 54mg 90mg Every 8-12 hours
9 lbs (4.1 kg) 41mg 61.5mg 102.5mg Every 8-12 hours
10 lbs (4.5 kg) 45mg 67.5mg 112.5mg Every 8-12 hours
12 lbs (5.4 kg) 54mg 81mg 135mg Every 8-12 hours
14 lbs (6.3 kg) 63mg 94.5mg 157.5mg Every 8-12 hours
16 lbs (7.3 kg) 73mg 109.5mg 182.5mg Every 8-12 hours
18 lbs (8.2 kg) 82mg 123mg 205mg (250mg tablet) Every 8-12 hours
20 lbs (9.1 kg) 91mg 136.5mg 227.5mg (250mg tablet) Every 8-12 hours
25 lbs (11.3 kg) 113mg 169.5mg 282.5mg (250mg tablet) Every 8-12 hours

Common Uses · 03

What is Keflex (Cephalexin) used for in cats?

Skin and soft tissue infections Urinary tract infections Wound infections Bone infections Respiratory infections

Administration · 04

How to give Keflex to your cat

Cephalexin capsules can be given whole, hidden inside a pill pocket or a small piece of deli meat or cheese. Do not open the capsule, as the powder inside tastes very unpleasant. If your cat refuses capsules, ask about the oral liquid suspension, which can be flavored. Use a pill gun to place the capsule at the back of your cat's tongue, hold the mouth closed, and stroke the throat until you see a swallow. Follow with a small syringe of water to ensure it goes down. Always give with food to reduce stomach upset. Complete the full course as prescribed.

Available Forms

Capsule, Tablet, Oral suspension

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Keflex in cats

Common side effects

Nausea and vomiting
Diarrhea
Decreased appetite
Drooling (if capsule is bitten)

Serious side effects — call your vet

  • Severe allergic reaction (anaphylaxis)
  • Persistent bloody diarrhea
  • Kidney damage (rare, at very high doses)
  • Blood disorders (rare)

Emergency · 06

When to call the vet

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

  • Signs of allergic reaction: facial swelling, hives, difficulty breathing
  • Persistent vomiting or severe diarrhea (especially bloody)
  • No improvement in infection after 3-4 days of treatment
  • Lethargy or refusal to eat for more than 24 hours
  • Rash, redness, or new skin lesions developing during treatment

For Dogs

Looking for Cephalexin dosage for dogs?

View the Cephalexin 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 Cephalexin.

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 15 mg per kg (6.80 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 cephalexin safe for cats?
Yes, cephalexin is generally considered safe and well-tolerated in cats. It is a first-generation cephalosporin antibiotic commonly prescribed for bacterial infections. Side effects are typically mild and mostly gastrointestinal (nausea, diarrhea). It is one of the safer antibiotic choices for cats when used at the correct dose and duration prescribed by your vet.
How long should my cat take cephalexin?
The typical course of cephalexin for cats is 7-14 days for most infections, though deep skin infections or bone infections may require 4-6 weeks or longer. It is very important to complete the entire course even if your cat appears better, as stopping early can lead to antibiotic resistance and recurrence of the infection.
Can I give my cat human cephalexin?
The active ingredient in human cephalexin is the same as veterinary formulations. However, you should never give your cat any medication without veterinary guidance, as the dose must be calculated specifically for your cat's weight and condition. Human capsules may also contain inactive ingredients not tested in cats. Always obtain antibiotics through your veterinarian.
What infections does cephalexin treat in cats?
Cephalexin is effective against many gram-positive bacteria and some gram-negative bacteria. In cats, it is commonly used for skin infections (wounds, abscesses, pyoderma), urinary tract infections, respiratory infections, and bone infections. It is not effective against all types of bacteria, so your vet may perform a culture and sensitivity test to confirm it is the right antibiotic.
What if my cat vomits after taking cephalexin?
Mild nausea is a common side effect. Giving cephalexin with food usually helps prevent vomiting. If your cat vomits within 30 minutes of dosing, you may need to re-dose—ask your vet. If vomiting persists despite giving with food, contact your vet about switching to a different antibiotic or trying a compounded formulation that may be easier on the stomach.

Safety · 10

More resources