Dog Cephalexin Dosage Calculator (15-30 mg/kg)
Calculate a dog's cephalexin dose by weight, using the 15-30 mg/kg per-dose veterinary range and the FDA-approved 22 mg/kg label dose, given twice daily.
Dog Dosage Calculator for Cephalexin
Always consult with your veterinarian before administering medication.
Documentation
Dog Cephalexin Dosage Calculator
Cephalexin is an antibiotic that veterinarians prescribe for bacterial infections in dogs, most often skin infections. This calculator estimates a cephalexin dose for a dog from its weight in kilograms, using the veterinary dosing range and the FDA-approved label dose as reference points.
A veterinarian sets the exact dose, schedule, and length of treatment for each dog. Use this calculator to check that math, not to replace a prescription.
How to Calculate Cephalexin Dosage for Dogs
Cephalexin for dogs is dosed per administration, not as one daily amount. Two sources set the numbers this calculator uses. The Merck Veterinary Manual lists a dosing range of 15 to 45 mg per kilogram, given every 6 to 12 hours. The FDA-approved label for the chewable-tablet brand Rilexine sets a fixed dose of 22 mg per kilogram (10 mg per pound), given twice a day for 28 days.
This calculator uses 15 to 30 mg/kg per dose, given twice a day, 12 hours apart. The lower bound is the Merck minimum; the upper bound sits inside the Merck range. That places the FDA label dose (22 mg/kg) inside the calculator's range, and it shows that figure alongside the range as a fixed reference point.
Cephalexin Dosage Formula
Minimum dose (mg) = weight (kg) × 15 mg/kg Maximum dose (mg) = weight (kg) × 30 mg/kg
The dose is given twice a day, so the daily total is double the per-dose amount:
Minimum daily total (mg) = minimum dose × 2 Maximum daily total (mg) = maximum dose × 2
Each per-dose amount is rounded to the nearest milligram. The calculator accepts weights in kilograms up to 120 kg (about 264 lb).
Worked Example
A 15 kg (33 lb) dog:
- Minimum dose: 15 kg × 15 mg/kg = 225 mg
- Maximum dose: 15 kg × 30 mg/kg = 450 mg
- Given every 12 hours, the daily total ranges from 450 mg to 900 mg.
- FDA label dose: 15 kg × 22 mg/kg = 330 mg per dose, or 660 mg a day.
Cephalexin Dosage Chart by Weight
| Dog weight | Per-dose range (15-30 mg/kg) | Daily total (twice daily) | FDA label dose (22 mg/kg, twice daily) |
|---|---|---|---|
| 5 kg (11 lb) | 75-150 mg | 150-300 mg | 110 mg per dose, 220 mg/day |
| 10 kg (22 lb) | 150-300 mg | 300-600 mg | 220 mg per dose, 440 mg/day |
| 15 kg (33 lb) | 225-450 mg | 450-900 mg | 330 mg per dose, 660 mg/day |
| 20 kg (44 lb) | 300-600 mg | 600-1,200 mg | 440 mg per dose, 880 mg/day |
| 25 kg (55 lb) | 375-750 mg | 750-1,500 mg | 550 mg per dose, 1,100 mg/day |
| 30 kg (66 lb) | 450-900 mg | 900-1,800 mg | 660 mg per dose, 1,320 mg/day |
These figures are starting points. A veterinarian may prescribe a dose above or below this range based on the infection and the dog's health.
Twice-Daily Dosing, Every 12 Hours
This calculator assumes a fixed schedule: one dose every 12 hours, twice a day. That matches the schedule on the FDA-approved cephalexin label for dogs. Some veterinarians prescribe a different interval, such as every 6 or 8 hours, for more severe infections, since the Merck Veterinary Manual allows dosing as often as every 6 hours. Always follow the schedule printed on the prescription label rather than the twice-daily default shown here, if the two differ.
What Cephalexin Treats in Dogs
Cephalexin is a first-generation cephalosporin antibiotic. It works by interfering with bacterial cell wall synthesis. The Rilexine label is approved for secondary superficial bacterial pyoderma (a skin infection) caused by susceptible Staphylococcus pseudintermedius, and recommends culture and susceptibility testing to confirm the cause.
Veterinarians also use oral cephalosporins for soft-tissue and some urinary tract infections. Cephalexin is not a good choice for every urinary infection: the Merck Veterinary Manual notes that it should be anticipated to be ineffective against E. coli, a common urinary pathogen. Like all antibiotics, it does not work against viruses, fungi or parasites.
Cephalexin Side Effects in Dogs
The most common adverse reactions in dogs are diarrhea, vomiting, loss of appetite and lethargy. If a dog vomits after a dose, giving it with a small amount of food may help. Allergic reactions can occur; fever, rash, difficulty breathing or pale gums are warning signs that need veterinary attention. The label contraindicates the drug in dogs allergic to cephalexin or to other beta-lactam antibiotics, the group that includes penicillins.
The kidneys clear cephalexin from the body, so a veterinarian may lower the dose in dogs with kidney dysfunction.
Frequently Asked Questions
What is the standard cephalexin dose for dogs?
The Merck Veterinary Manual gives 15 to 45 mg per kilogram per dose, every 6 to 12 hours. The FDA-approved label dose for the Rilexine brand is 22 mg/kg twice daily. This calculator shows 15 to 30 mg/kg per dose, twice daily, alongside the label dose.
How many times a day should a dog take cephalexin?
Twice a day, about 12 hours apart, is the standard schedule and the one this calculator uses. A veterinarian may prescribe a shorter interval, such as every 6 or 8 hours, for a more severe infection.
How do I calculate my dog's cephalexin dose?
Multiply the dog's weight in kilograms by 15 for the low end of the per-dose range, and by 30 for the high end. Multiply each result by 2 to get the daily total, since the dose is given twice a day.
Can I give my dog cephalexin with food?
Yes. According to the Rilexine label, food lowers the peak blood level but has a negligible effect on how much of the drug is absorbed. A small amount of food may help if the dog vomits after a dose.
What should I do if I miss a dose?
Give the missed dose as soon as it is remembered, unless the next dose is almost due. In that case, skip the missed dose and resume the normal schedule. Do not give two doses at once.
Is human cephalexin the same as the dog version?
The active ingredient is the same, but the dose for a dog depends on its weight and the infection, and human capsules come in fixed strengths. Use cephalexin for a dog only under veterinary direction.
References
- U.S. Food and Drug Administration / DailyMed. Rilexine (cephalexin) chewable tablets, label. Rilexine label on DailyMed — 22 mg/kg (10 mg/lb) twice daily for 28 days; pyoderma indication; mechanism; adverse reactions; beta-lactam allergy contraindication; effect of food.
- Merck Veterinary Manual. Dosages of Cephalosporins. Merck cephalosporin dosage table — cephalexin in dogs, 15–45 mg/kg PO every 6–12 hours.
- Merck Veterinary Manual. Cephalosporins and Cephamycins Use in Animals. Merck cephalosporins chapter — cephalexin is first-generation; expected to be ineffective against E. coli.
- VCA Animal Hospitals. Cephalexin. VCA cephalexin drug information — missed-dose guidance; giving with food after vomiting; caution and lower doses with kidney dysfunction.