Medication Guide • Reviewed by Dr. Tiffany Delacruz, DVM
Cephalexin for Dogs
Cephalexin is a prescription antibiotic widely used in dogs for skin infections, urinary tract infections, and other susceptible bacterial infections.
What Cephalexin is used for in dogs
- Skin infections (pyoderma)
- Urinary tract infections
- Some respiratory infections
- Bone and joint infections
How it works
Cephalexin inhibits bacterial cell wall synthesis, killing susceptible bacteria. It's effective against many Gram-positive bacteria and some Gram-negative.
Available formulations
250 mg capsule
500 mg capsule
Oral suspension
Side effects to know
Common side effects
- • Mild GI upset
- • Diarrhea
- • Decreased appetite
These usually resolve on their own. If they persist past the first few doses, ask your vet.
Call your vet immediately if you see
- ⚠ Severe allergic reaction (especially in penicillin-allergic dogs)
- ⚠ Severe diarrhea (C. difficile risk)
- ⚠ Yeast overgrowth with long courses
Drug interactions
- • Probenecid (increases cephalexin levels)
- • Aminoglycoside antibiotics (kidney monitoring)
When not to use
- • Known cephalosporin allergy
- • Use cautiously in penicillin-allergic dogs
- • Severe kidney disease (dose adjustment)
Monitoring during treatment
Complete the full prescribed course. Watch for signs of allergic reaction or severe GI upset.
Need a Cephalexin refill?
RexVet is the first 501(c)(3) non-profit online vet service in the U.S. Talk to a licensed veterinarian by video, get your dogs's Cephalexin prescription, and have it shipped through RexVetRx — all for $64.99 per visit.
Book a vet visit — $64.99Cephalexin for Dogs
Frequently asked questions
How long until cephalexin works for my dog's skin infection?
Most dogs show clinical improvement within 3-5 days. Skin infections typically require 2-4 weeks of treatment — finish the full course even if your dog looks better.
Should I give cephalexin with food?
It can be given with or without food, but with food often reduces GI upset.
Can I give my dog human cephalexin?
Same active ingredient — but only at vet-determined doses. Some human capsules contain dyes or coatings unsuitable for sensitive dogs.
Can RexVet prescribe cephalexin?
Yes — for clearly diagnosable cases like uncomplicated skin or urinary infections, a RexVet video visit can result in cephalexin through RexVetRx the same day.
What if the infection comes back after cephalexin?
Recurrent infections often need culture and sensitivity testing to find the right antibiotic. A RexVet vet can help organize that workup.
Medical review by Dr. Tiffany Delacruz, DVM
Chief Executive Officer & Lead Veterinarian, RexVet. Licensed in Florida, New York, and Virginia.
Last fact-checked: 2026-05-19
Sources
This page is an educational reference and does not replace veterinary advice. Always consult a licensed veterinarian before starting, changing, or stopping medication for your pet.