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PetDosageChart

Antibiotic (Cephalosporin) · For Dogs

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

Standard Cephalexin dose for dogs is 22 mg per kg (9.98 mg per lb), given every 8-12 hours. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

Onset
1-2 hours
Duration
8-12 hours
Class
Antibiotic (Cephalosporin)

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 dog weight

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Dosage Chart · 02

Keflex dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
5 lbs (2.3 kg) 23mg 50.5mg 69mg every 8-12 hours
10 lbs (4.5 kg) 45mg 99mg 135mg every 8-12 hours
15 lbs (6.8 kg) 68mg 149.5mg 204mg (250mg tablet) every 8-12 hours
20 lbs (9.1 kg) 91mg 200mg (250mg tablet) 273mg (250mg tablet) every 8-12 hours
25 lbs (11.3 kg) 113mg 248.5mg (250mg tablet) 339mg every 8-12 hours
30 lbs (13.6 kg) 136mg 299mg (250mg tablet) 408mg every 8-12 hours
40 lbs (18.1 kg) 181mg 398mg 543mg (2 × 250mg) every 8-12 hours
50 lbs (22.7 kg) 227mg (250mg tablet) 499.5mg (2 × 250mg) 681mg every 8-12 hours
60 lbs (27.2 kg) 272mg (250mg tablet) 598.5mg 816mg every 8-12 hours
70 lbs (31.7 kg) 317mg 697.5mg (3 × 250mg) 951mg (4 × 250mg) every 8-12 hours
80 lbs (36.3 kg) 363mg 798.5mg (3 × 250mg) 1089mg every 8-12 hours
90 lbs (40.8 kg) 408mg 897.5mg 1224mg (5 × 250mg) every 8-12 hours
100 lbs (45.4 kg) 454mg (2 × 250mg) 999mg (4 × 250mg) 1362mg every 8-12 hours
120 lbs (54.4 kg) 544mg (2 × 250mg) 1197mg (5 × 250mg) 1632mg every 8-12 hours
150 lbs (68 kg) 680mg 1496mg (6 × 250mg) 2040mg (8 × 250mg) every 8-12 hours

Common Uses · 03

What is Keflex (Cephalexin) used for in dogs?

skin infections (pyoderma) urinary tract infections bone infections wound infections

Administration · 04

How to give Keflex to your dog

Cephalexin can be given with or without food, but giving with food reduces stomach upset. Complete the entire prescribed course, even if your dog seems better. For skin infections, treatment often needs to continue for 3-4 weeks or longer.

Available Forms

capsule, tablet, liquid suspension

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Keflex in dogs

Common side effects

nausea
vomiting
diarrhea
decreased appetite

Serious side effects — call your vet

  • allergic reaction (hives, swelling)
  • severe diarrhea
  • blood in stool
  • seizures (rare, very high doses)

Emergency · 06

When to call the vet

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

  • Signs of allergic reaction (facial swelling, hives, difficulty breathing)
  • Severe or bloody diarrhea
  • Vomiting that does not resolve
  • No improvement after 3-5 days
  • Rash or skin reaction develops

For Cats

Looking for Cephalexin dosage for cats?

View the Cephalexin dosage chart and calculator for cats.

Related · 08

Related medications for dogs

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 22 mg per kg (9.98 mg per lb) of body weight, given every 8-12 hours. The calculator multiplies that basis by your dog'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 dogs dosage data.

Frequently Asked · 07

Questions about this medication

What is cephalexin used for in dogs?
Cephalexin is one of the most commonly prescribed antibiotics for dogs. It is especially effective for skin infections (pyoderma), urinary tract infections, wound infections, and bone infections. It works by killing bacteria by disrupting their cell wall formation.
How much cephalexin do I give my dog?
The standard dose is 22 mg per kilogram of body weight, given every 12 hours. For example, a 50 lb (23 kg) dog would typically receive 500 mg twice daily. Your vet may adjust the dose based on the type and severity of infection.
How long should a dog take cephalexin?
Treatment duration depends on the infection. Simple urinary tract infections may need 7-14 days. Skin infections (pyoderma) often require 3-4 weeks or even longer for deep infections. Always complete the full prescribed course.
Is cephalexin safe for dogs?
Cephalexin is considered very safe for dogs and is one of the most commonly prescribed veterinary antibiotics. The most common side effects are mild GI upset (nausea, diarrhea). Serious allergic reactions are rare but possible, especially in dogs with known penicillin allergies.

Safety · 10

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