cat-cephalexin-dosage-calculator

Cat Cephalexin Dosage Calculator

The cat cephalexin dosage calculator estimates how many milligrams of cephalexin to give a cat, based on the cat's body weight. It uses a rate of 22 mg per kilogram (about 10 mg per pound), given twice a day. That rate is the label dose for dogs, 22 mg/kg every 12 hours. In cats, cephalexin is used extra-label (outside its approved species), and a veterinary teaching hospital lists 15 to 30 mg/kg every 12 hours for soft-tissue infections in cats.

What Is Cephalexin?

Cephalexin is an antibiotic in the cephalosporin class. It is sold under brand names such as Keflex for human use. Veterinarians prescribe it for cats mainly for bacterial skin and soft-tissue infections. It works by killing bacteria.

Cephalexin only works against bacteria. It does not work for viral infections, and it does not treat fungal infections. A cat needs a prescription from a veterinarian to get it; there is no over-the-counter version made for pets.

How to Calculate Cephalexin Dosage for Cats

1. Weigh the cat, or find its most recent weight from a vet visit.
2. Enter the weight into the calculator.
3. Choose the weight unit: pounds (lb) or kilograms (kg).
4. Read the dosage shown. This is the amount for one dose, given twice a day.

Cephalexin Dosage Formula

The calculator uses one of two fixed rates, depending on the unit chosen:

• 10 mg per pound of body weight (lb)
• 22 mg per kilogram of body weight (kg)

Both rates describe nearly the same dose. 22 mg/kg works out to about 9.98 mg per pound, so the two results differ by about 0.2%.

The dose is given twice daily, about 12 hours apart. That schedule is often written as "BID," short for the Latin phrase bis in die.

Formula:

1Dose per administration = body weight × rate
2

Worked Example

A cat weighs 10 lb. Using the pound rate:

110 lb × 10 mg/lb = 100 mg per dose
2

The cat receives 100 mg in the morning and 100 mg in the evening, for a total of 200 mg per day.

A second example in metric units: a cat weighs 4 kg.

14 kg × 22 mg/kg = 88 mg per dose
2

That cat receives 88 mg twice a day, for a total of 176 mg per day.

Cephalexin Dosage Chart by Weight

These figures use the 10 mg/lb rate. A veterinarian may prescribe a different amount depending on the type and severity of the infection.

What Cephalexin Treats in Cats

Cephalexin is a first-line choice for skin infections caused by susceptible Staphylococcus bacteria. It is also used for:

• Other soft-tissue infections, including wounds and abscesses
• Some urinary tract infections, where it is a less preferred choice
• Infections that spread through the body, when a culture test shows the bacteria are susceptible

Giving Cephalexin Safely

• Give cephalexin only on a veterinarian's instructions. Do not give a cat medication made for humans, or leftover medication from another animal, without checking with a vet first.
• Finish the full course of doses, even if the cat seems better partway through. Stopping early can let surviving bacteria multiply again.
• If a dose is missed, give it as soon as it is remembered. If it is almost time for the next dose, skip the missed one; do not give a double dose.
• Store the medication as the label directs. Liquid cephalexin is kept in the refrigerator and thrown away after 14 days.
• Common side effects are mild stomach upset, such as vomiting, diarrhea, or reduced appetite. Contact a veterinarian if side effects are severe or do not go away.

Frequently Asked Questions

How much cephalexin should a 10-pound cat get?

At the standard rate of 10 mg per pound, a 10 lb cat gets 100 mg per dose, twice a day, for a total of 200 mg daily. A veterinarian may adjust this based on the infection being treated.

Is cephalexin the same as amoxicillin?

No. Cephalexin is a cephalosporin, and amoxicillin is a penicillin. They belong to different classes of antibiotic and are not interchangeable without a veterinarian's guidance.

Can a cat take human cephalexin?

Only under a veterinarian's direction. The active drug is the same, but tablet strengths, flavorings, and other ingredients in human products are not made with a cat's needs in mind. A veterinarian will prescribe a form and strength suited to the cat.

What happens if a dose is missed?

Give the missed dose as soon as it is noticed. If it is close to the time for the next dose, skip the missed one and continue on the normal schedule. Never give two doses at once to make up for a missed one.

What are the side effects of cephalexin in cats?

The most common side effects are digestive: vomiting, diarrhea, or loss of appetite. Allergic reactions are possible but less common. A cat showing swelling, hives, or difficulty breathing needs urgent veterinary care.

Does cephalexin treat every kind of infection?

No. It works only against bacteria. It has no effect on viral infections, such as most upper respiratory infections in cats, or on fungal infections like ringworm.

When to Contact a Veterinarian

Contact a veterinarian promptly if a cat taking cephalexin shows severe vomiting or diarrhea, signs of an allergic reaction, or no improvement after a few days of treatment.

This calculator gives a general estimate based on a standard veterinary dosing rate. It is not a substitute for a veterinarian's prescription or advice. Always follow the dose and schedule a veterinarian provides.

References

1. The Ohio State University College of Veterinary Medicine. OSU VMC Antimicrobial Use Guidelines: Cephalexin [Companion]. Cephalexin dosing for cats and dogs — dog label dose 22 mg/kg every 12 hours; cats 15 to 30 mg/kg every 12 hours for soft-tissue infections (extra-label); first-line use for staphylococcal pyoderma; less preferred for urinary tract infections.
2. U.S. National Library of Medicine, MedlinePlus. Cephalexin. MedlinePlus drug information: cephalexin — cephalosporin class; not effective for viral infections; liquid kept refrigerated and discarded after 14 days.