Cephalexin Dosage for Cats Calculator (mg/kg)
Calculate cephalexin dosage for your cat by weight, infection type, and formulation, with dose, frequency, and duration.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Dose (mg) = Weight (kg) x Dose Rate (mg/kg); Volume (ml) = Dose (mg) / Concentration (mg/ml)
The cephalexin dose is calculated by multiplying the cat's body weight in kilograms by the prescribed dose rate (typically 15-30 mg/kg). For liquid formulations, the volume is determined by dividing the calculated dose in milligrams by the concentration of the suspension. The total medication needed is calculated by multiplying the daily dose by the treatment duration in days.
Worked Examples
Example 1: Skin Infection in Adult Cat
Problem:Calculate cephalexin dose for a 10-lb cat with a skin infection using liquid 125mg/5ml formulation.
Solution:Weight: 10 lbs = 4.5 kg\nStandard dose: 22.5 mg/kg twice daily\nDose per administration: 22.5 x 4.5 = 101.3 mg\nLiquid 125mg/5ml = 25mg/ml\nVolume per dose: 101.3 / 25 = 4.05 ml\nFrequency: Twice daily for 21 days\nTotal liquid needed: 4.05 x 2 x 21 = 170 ml
Result:4.05 ml twice daily for 21 days (101.3 mg per dose)
Example 2: UTI in Small Cat
Problem:Calculate cephalexin dose for a 7-lb cat with a urinary tract infection using 250mg capsules.
Solution:Weight: 7 lbs = 3.2 kg\nStandard dose: 18.5 mg/kg twice daily\nDose per administration: 18.5 x 3.2 = 59.2 mg\n250mg capsule: 59.2 / 250 = 0.24 capsules\nNote: Capsules cannot be easily split; liquid form recommended\nFrequency: Twice daily for 14 days
Result:59.2 mg twice daily for 14 days — liquid form recommended for accurate dosing
Frequently Asked Questions
What is cephalexin and is it safe for cats?
Cephalexin (brand name Keflex) is a first-generation cephalosporin antibiotic that is commonly prescribed for cats by veterinarians. It works by disrupting bacterial cell wall synthesis, making it effective against many gram-positive bacteria and some gram-negative bacteria. While not FDA-approved specifically for cats, it is widely used as an extra-label or off-label medication in veterinary practice with a well-established safety profile. Cephalexin is generally well-tolerated in cats, though side effects can include gastrointestinal upset (vomiting, diarrhea, decreased appetite) in some individuals. It should not be given to cats with known allergies to cephalosporin or penicillin-class antibiotics.
What is the correct cephalexin dosage for cats?
The standard veterinary dosage of cephalexin for cats is 15-30 mg per kilogram of body weight, given twice daily (every 12 hours). For most infections, a dose of 22 mg/kg twice daily is commonly prescribed. Some severe infections like bone infections may require doses at the higher end of the range given three times daily. The exact dose depends on the type and severity of infection, the cat size, and their overall health. Treatment duration typically ranges from 7-42 days depending on the infection. It is crucial to complete the full prescribed course even if symptoms improve to prevent antibiotic resistance. Only a veterinarian should determine the appropriate dose for your specific cat.
What infections does cephalexin treat in cats?
Cephalexin is effective against a range of bacterial infections in cats. Common uses include skin infections (pyoderma, abscesses, wound infections), urinary tract infections (UTIs), upper respiratory infections, bone and joint infections (osteomyelitis), and soft tissue infections. It is particularly effective against Staphylococcus and Streptococcus species, which are common causes of skin and wound infections in cats. Cephalexin is also used prophylactically before certain surgical procedures to prevent post-operative infections. It is not effective against viral infections (like feline herpesvirus or calicivirus) or certain resistant bacteria like MRSA. Your veterinarian may perform a culture and sensitivity test to confirm cephalexin is appropriate for your cat specific infection.
Can I give my cat human cephalexin?
While the active ingredient is the same, you should NEVER give your cat human cephalexin without veterinary guidance. The dosage for cats is calculated differently than for humans, and human formulations may contain inactive ingredients, flavorings, or coatings that could be harmful to cats. Some liquid suspensions contain xylitol or other sweeteners that are toxic to animals. Additionally, the correct dose, frequency, and duration depend on an accurate diagnosis — giving antibiotics without proper veterinary diagnosis can worsen the condition, mask symptoms of serious illness, or contribute to antibiotic resistance. Always consult your veterinarian, who can prescribe the appropriate veterinary formulation and dosage for your cat specific condition.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy