What is Keflex: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Keflex overview

BRAND NAMES:

  • Keflex

Generic Names:

  • Cephalexin

Uses:

  • Treats infections. This medicine is a cephalosporin antibiotic.

Therapeutic Classes:

  • Antibiotic

Forms:

  • Capsule, Tablet, Tablet for Suspension, Liquid

How it’s taken:

  • By mouth

What is Keflex used for?

Keflex is a cephalosporin antibiotic used to treat bacterial infections such as acne and prevention of bacterial endocarditis. It also treats upper respiratory tract infections, ear infections, skin infections, and urinary tract infections. This medication is indicated for use by patients 1 year and above. This medication is available as a capsule.

What form(s) does Keflex come in

  • Capsule

  • Tablet

  • Tablet for Suspension

  • Liquid

What are common Keflex doses?

Common Keflex prescriptions

  • Keflex
    20 capsules bottle

  • Keflex
    40 capsules bottle

  • Keflex
    250mg capsule

  • Keflex
    500mg capsule

  • Keflex
    750mg capsule

How to take Keflex

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • You may take your medicine with food or milk to avoid stomach upset.

  • Oral liquid: Shake well just before use. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.

  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

  • Capsule or tablet: Store at room temperature away from heat, moisture, and direct light.

  • Oral liquid: Store in the refrigerator for 14 days. After 14 days, throw away any unused medicine. Do not freeze.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

  • You may take your medicine with food or milk to avoid stomach upset.

  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.

  • Oral liquid: Store in the refrigerator for 14 days. After 14 days, throw away any unused medicine. Do not freeze.

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • Oral liquid: Shake well just before use. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.

  • Capsule or tablet: Store at room temperature away from heat, moisture, and direct light.

What to do if you miss a dose of Keflex

Keflex contraindications

  • This medicine is not right for everyone. Do not use this medicine if you had an allergic reaction to cephalexin or another cephalosporin medicine.

Keflex warnings

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, or a history of digestive problems, such as colitis. Tell your doctor if you are allergic to penicillin.

  • This medicine can cause diarrhea. Call your doctor if the diarrhea becomes severe, does not stop, or is bloody. Do not take any medicine to stop diarrhea until you have talked to your doctor. Diarrhea can occur 2 months or more after you stop taking this medicine.

  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.

  • Call your doctor if your symptoms do not improve or if they get worse.

Keflex interactions

  • Some medicines and foods can affect how cephalexin works. Tell your doctor if you are also usingMetforminProbenecid

  • This medicine can cause diarrhea. Call your doctor if the diarrhea becomes severe, does not stop, or is bloody. Do not take any medicine to stop diarrhea until you have talked to your doctor. Diarrhea can occur 2 months or more after you stop taking this medicine.

  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.

  • Call your doctor if your symptoms do not improve or if they get worse.

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Keflex side effects

Serious Side Effects

  • Blistering, peeling, red skin rash

  • Severe diarrhea, especially if bloody or ongoing

  • Severe stomach pain, vomiting

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Less Serious Side Effects

  • Mild diarrhea or nausea

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