Antibiotic (Cephalosporin) · For Dogs

Cephalexin dosage reference for dogs (Keflex)

This page's standard weight-based reference is 22 mg per kg (9.98 mg per lb), with every 12 hours recorded as the reference frequency. Use the calculator to see the arithmetic for your dog's weight, then confirm the indication, product, and actual dose with a veterinarian.

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

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Sources and review process

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Cephalexin (often known by brand names such as Keflex and Rilexine) is an antibiotic (cephalosporin) commonly used in veterinary medicine for skin infections (pyoderma), urinary tract infections, bone infections, and wound infections. Understanding the correct dosage, administration, and potential side effects of Cephalexin is critical for your dog’s safety and well-being.

A typical Cephalexin dose for dogs is around 22 mg/kg every 12 hours (the FDA-approved Rilexine label dose for skin infections), within a usual range of 10-30 mg/kg. Some infections, such as bone infections, may be treated on a shorter interval, but only as your veterinarian directs. Available forms include capsule, tablet, and liquid suspension.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

What the source establishes

The label dose is 22 mg/kg (10 mg/lb) of body weight twice daily for 28 days, for secondary superficial bacterial pyoderma in dogs caused by susceptible Staphylococcus pseudintermedius. This is why the page records cephalexin as every 12 hours.

This is the canine skin-infection label. Shorter dosing intervals used for other infections, such as bone infections, are extra-label and set by the veterinarian; this page does not model them.

RILEXINE (cephalexin) chewable tablets FDA-approved label (Virbac, DailyMed) — Indications; Dosage and Administration (revision 01/2024).

Dogs in the comparison group received cephalexin at 15–30 mg/kg by mouth twice daily, and all dogs in both groups reached resolution. This supports the 30 mg/kg upper per-dose reference on a twice-daily schedule (60 mg/kg per day).

A 40-dog open study of superficial pyoderma. It does not set the dose for other infections or for an individual dog.

Toma et al. (2008): once-daily vs twice-daily cephalexin in canine superficial pyoderma — J Small Anim Pract 49:384–391; abstract, methods.

Cephalexin Dosage Calculator for Dogs

Enter your dog’s weight below to estimate the Cephalexin dose from the 22 mg/kg guideline. Your veterinarian may adjust it for your dog’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your dog's weight

Quick Dosage Chart

Typical Cephalexin amounts for common dog weights, for quick reference:

Dosage Chart · 02

Keflex weight-based reference chart for dogs

Scroll sideways to see full table

Keflex weight-based reference chart. Educational arithmetic, not a prescription.
Weight	Lower Reference	Standard Reference	Upper Reference	Frequency
5 lbs (2.3 kg)	22.7 mg	49.9 mg	68.0 mg (0.25 × 250mg)	every 12 hours
10 lbs (4.5 kg)	45.4 mg	99.8 mg	136.1 mg (0.5 × 250mg)	every 12 hours
15 lbs (6.8 kg)	68.0 mg (0.25 × 250mg)	149.7 mg	204.1 mg (0.75 × 250mg)	every 12 hours
20 lbs (9.1 kg)	90.7 mg	199.5 mg (0.75 × 250mg)	272.1 mg (250mg tablet)	every 12 hours
25 lbs (11.3 kg)	113.4 mg	249.4 mg (250mg tablet)	340.1 mg (1.25 × 250mg)	every 12 hours
30 lbs (13.6 kg)	136.1 mg (0.5 × 250mg)	299.3 mg (1.25 × 250mg)	408.2 mg	every 12 hours
40 lbs (18.1 kg)	181.4 mg (0.75 × 250mg)	399.1 mg (1.5 × 250mg)	544.2 mg (2 × 250mg)	every 12 hours
50 lbs (22.7 kg)	226.8 mg	498.9 mg (2 × 250mg)	680.3 mg (2.5 × 250mg)	every 12 hours
60 lbs (27.2 kg)	272.1 mg (250mg tablet)	598.6 mg (2.5 × 250mg)	816.3 mg	every 12 hours
70 lbs (31.7 kg)	317.5 mg (1.25 × 250mg)	698.4 mg (3 × 250mg)	952.4 mg	every 12 hours
80 lbs (36.3 kg)	362.8 mg (1.5 × 250mg)	798.2 mg (3 × 250mg)	1088.4 mg	every 12 hours
90 lbs (40.8 kg)	408.2 mg (1.75 × 250mg)	898.0 mg (3.5 × 250mg)	1224.5 mg	every 12 hours
100 lbs (45.4 kg)	453.5 mg (1.75 × 250mg)	997.7 mg (4 × 250mg)	1360.5 mg	every 12 hours
120 lbs (54.4 kg)	544.2 mg (2 × 250mg)	1197.3 mg (5 × 250mg)	1632.7 mg (6.5 × 250mg)	every 12 hours
150 lbs (68 kg)	680.3 mg (2.5 × 250mg)	1496.6 mg (6 × 250mg)	2040.8 mg (8 × 250mg)	every 12 hours

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Keflex reference by dog weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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How to Give Cephalexin 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.

It is generally recommended to give Cephalexin with food to help reduce stomach upset. It may interact with aminoglycoside antibiotics (increased nephrotoxicity), probenecid, and anticoagulants.

Side Effects and Safety

Common side effects include nausea, vomiting, diarrhea, and decreased appetite. More serious side effects can occur, such as allergic reaction (hives, swelling), severe diarrhea, blood in stool, and seizures (rare, very high doses).

Cautions · 12

When Keflex should be used with caution or avoided

Some dogs should not take Keflex, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Keflex.

known penicillin or cephalosporin allergy
severe kidney disease (dose adjustment needed)

Interactions · 13

Keflex drug interactions

Keflex can interact with other drugs. This list is not complete — always give your veterinarian a full list of your dog's medications and supplements.

aminoglycoside antibiotics (increased nephrotoxicity)

probenecid

anticoagulants

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult dog at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

In an emergency, or after accidental ingestion or a suspected overdose
For pregnant or nursing pets
For very young or very old dogs
For pets with liver disease, kidney disease, or another chronic illness
For pets taking several medications at once
When you are not sure of your dog's current, accurate weight
For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your dog had too much Keflex, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

Call your veterinarian or the nearest emergency animal hospital.
ASPCA Animal Poison Control Center: (888) 426-4435
Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your dog experiences any of the following, contact your veterinarian or an emergency clinic immediately:

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

Frequently Asked Questions

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, which matches the FDA-approved Rilexine label for skin infections. For example, a 50 lb (23 kg) dog would typically receive 500 mg twice daily. Your vet may adjust the dose or, for some infections such as bone infections, prescribe a shorter interval.

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.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your dog's weight by the lower, standard, and upper mg/kg values recorded for Keflex. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: skin infections (pyoderma), urinary tract infections, bone infections, wound infections
Recorded forms: capsule, tablet, liquid suspension
Reference timing: every 12 hours; onset 1-2 hours; duration 12 hours

Individual checks a calculator cannot perform

Confirm the diagnosis and the reason this medication is being considered.
Match the exact product, concentration, route, and whether a tablet may be split.
Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

known penicillin or cephalosporin allergy; severe kidney disease (dose adjustment needed).

Recorded interactions

aminoglycoside antibiotics (increased nephrotoxicity); probenecid; anticoagulants.

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your dog's complete medication list before acting on a number.

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

RILEXINE (cephalexin) chewable tablets FDA-approved label (Virbac, DailyMed)
Indications; Dosage and Administration (revision 01/2024). Supports the specific claim described above; it is not a review of the entire page.
Toma et al. (2008): once-daily vs twice-daily cephalexin in canine superficial pyoderma
J Small Anim Pract 49:384–391; abstract, methods. Supports the specific claim described above; it is not a review of the entire page.
Plumb's Veterinary Drug Handbook — listed in this medication's source record.
Merck Veterinary Manual — listed in this medication's source record.
DailyMed label search for Cephalexin — check current product and formulation labels; some veterinary uses may be off-label.

Specific citations above support the identified claims. Other source names remain record-level references; further claim review is still needed. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

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 12 hours. The calculator multiplies that basis by your dog's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner: Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status: Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review dogs dosage data.

Safety · 10

More resources

Pet Medication Safety Hub — What's safe, what's dangerous, and emergency signs
How we calculate dosages — Our sources, math, and review process
Printable emergency checklist — One-page reference for your fridge or first aid kit