Dose scales with body weight and infection severity
Cephalexin is dosed by the dog's weight, in milligrams per kilogram. Vets pick the mg/kg figure from how serious the infection is, then split the daily total across two or three servings. A 20 kg dog with a mild skin infection at 15 mg/kg gets 300 mg per serving; twice a day that is 600 mg a day. This is a first-generation cephalosporin antibiotic and its use in dogs is often off-label, so the exact figure should come from your vet.
Typical mg/kg by infection severity
| Infection | Dose (mg/kg) | Dose (mg/lb) |
|---|---|---|
| Mild | 10–15 | 4.5–6.8 |
| Moderate | 15–25 | 6.8–11.3 |
| Severe | 25–40 | 11.3–18.1 |
Dosing frequency is usually every 12 hours (twice a day) or every 8 hours (three times a day). Maximum safe daily total for a dog with healthy kidneys is around 80 mg/kg. This is general information, not veterinary advice.
Tablet strengths and what to watch for
- Capsule sizes. Cephalexin comes as 250 mg and 500 mg capsules, plus 100/300/600 mg chewable tablets and a liquid; the calculator rounds a target dose up to whole units.
- Kidney disease. Dogs with reduced kidney function need a lower dose. Cephalexin is cleared by the kidneys, so it can build up otherwise.
- Allergy overlap. Dogs allergic to penicillin can react to cephalosporins in a small share of cases. Stop and call your vet if you see swelling, hives or trouble breathing.
- Never use human leftovers. Use the veterinary product your vet prescribed. Strength and inactive ingredients can differ.
Common questions
What is the standard cephalexin dose for a dog?
A common range is 15 to 25 mg per kg of body weight, given twice a day (every 12 hours). For a 20 kg dog that is roughly 300 to 500 mg per dose. Your vet may set a different dose for the specific infection, so confirm before you start.
Can I give cephalexin with food?
Yes. Cephalexin can be given with or without food. Giving it with a meal can reduce nausea, though it may slow absorption slightly.
How long does a course usually last?
Most infections are treated for 7 to 14 days. Superficial skin infections (pyoderma) can need up to 28 days, and deep pyoderma several weeks. Finish the full course even if the dog seems better.
