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, including skin infections and urinary tract 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.
This calculator uses 15 to 30 mg/kg per dose, given twice a day, 12 hours apart. 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
The calculator accepts weights up to 120 kg (about 264 lb), which covers giant breeds such as Mastiffs and Great Danes.
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 kills bacteria by disrupting their cell walls. Veterinarians use it most often for skin infections, such as pyoderma (a bacterial skin infection) and infected wounds, usually for 7 to 14 days. It also treats urinary tract infections caused by bacteria such as E. coli, since it reaches high concentrations in urine.
Cephalexin can also treat some respiratory infections, ear infections, and dental infections, though a veterinarian first confirms the infection is bacterial rather than viral or fungal. It does not work against viruses, fungi such as yeast, or parasites.
Cephalexin Side Effects in Dogs
The most common side effect is stomach upset: vomiting, diarrhea, or loss of appetite. Giving the medication with food usually reduces this. Allergic reactions are rare but serious. Warning signs include hives, facial swelling, and difficulty breathing; these need immediate veterinary attention. Dogs that have reacted to penicillin-type antibiotics have a higher chance of reacting to cephalexin too, because the two drug families are chemically related.
Dogs with severe kidney disease need extra care, since the kidneys clear cephalexin from the body. A veterinarian may lower the dose or choose a different antibiotic for these dogs.
Frequently Asked Questions
What is the standard cephalexin dose for dogs?
Veterinary references put it at 15 to 30 mg per kilogram of body weight per dose, given twice a day. The FDA-approved label dose for the Rilexine brand is a fixed 22 mg/kg, also twice daily.
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. Food does not reduce how well cephalexin is absorbed, and giving it with a meal usually lowers the chance of stomach upset.
What should I do if I miss a dose?
Give the missed dose as soon as it is noticed, unless the next dose is due soon. In that case, skip the missed dose and resume the normal schedule. Do not give a double dose to make up for a missed one.
Is human cephalexin the same as the dog version?
The active ingredient is identical, but the correct dose depends on the dog's exact weight, and human products may contain inactive ingredients that are unsafe for dogs. Use cephalexin for a dog only under veterinary direction.
References
- U.S. Food and Drug Administration. Rilexine (cephalexin) chewable tablets, prescribing information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=84506621-8429-4b65-a7b4-1c9375dcbd89
- Merck Veterinary Manual. Dosages of Cephalosporins. https://www.merckvetmanual.com/multimedia/table/dosages-of-cephalosporins
- Plumb, D.C. (2018). Plumb's Veterinary Drug Handbook (9th ed.). Wiley-Blackwell.