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PetDosageChart

Keflex (Cephalexin) Dosage for Cats

First-Generation Cephalosporin Antibiotic ⏱ Onset: 1-2 hours ⏳ Duration: 8-12 hours per dose

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. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

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Keflex Dosage Chart for Cats by Weight

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Weight Low Dose Standard Dose Max Dose 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

What is Keflex (Cephalexin) used for in cats?

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

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 of Keflex in cats

Common side effects

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

Serious side effects

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

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

Related Medications for Cats

Fluoroquinolone antibiotic

Baytril

Enrofloxacin

For bacterial infections

View dosage chart
Antibiotic (Penicillin)

Amoxil

Amoxicillin

For bacterial infections

View dosage chart
Antibiotic (Tetracycline)

Vibramycin

Doxycycline

For upper respiratory infections

View dosage chart
Nitroimidazole Antibiotic / Antiprotozoal

Flagyl

Metronidazole

For Inflammatory bowel disease (IBD)

View dosage chart

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.

Frequently Asked Questions

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.

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