Generic name: Cephalexin hydrochloride.

Other brand names: Keflet, Keftab.

Keflex is a cephalosporin antibiotic. It prevents bacteria from multiplying and growing.

Quick Facts About Keflex


Used to treat bacterial infections of the respiratory tract including: middle ear, bone, skin, and the reproductive and urinary systems.

Keflex Dosage

May take with or without meals. Take at evenly spaced intervals, per your doctor’s instructions. Finish all of the medication even if symptoms subside. Tablets are for adults only. Do not use with other people or for other infections without advice from your doctor.

  • Usual adult dose: for throat, skin, and urinary tract infections — 500 milligrams taken every 12 hours. Bladder infection therapy is for 7 to 14 days. For other infections — 250 milligrams taken every 6 hours.
  • Usual child dose: only capsules and oral suspension are prescribed for children, not tablets. 25 to 50 milligrams per each 2.2 pounds of body weight per day, divided into smaller doses. For strep throat in children over 1 year and for skin infections — 2 doses taken every 12 hours. Should take for 10 days in the case of strep throat. For middle ear infection — 75 to 100 milligrams per each 2.2 pounds of body weight per day, divided into smaller doses.
  • Missed dose: take as soon as possible. If taking 2 times per day — take next dose in 5 to 6 hours. If taking 3 or more times per day — take next dose 2 to 4 hours later. Then go back to regular schedule.

Keflex Side Effects

Overdose symptoms:

blood in urine, diarrhea, nausea, upper abdominal pain, vomiting. If you suspect an overdose, immediately seek medical attention.

More common side effects: diarrhea.

Less common or rare Keflex side effects: abdominal pain, agitation, colitis, confusion, dizziness, fatigue, fever, genital and rectal itching, hallucinations, headache, hepatitis, hives, indigestion, inflammation of joints, inflammation of stomach, joint pain, nausea, rash, seizures, severe allergic reaction, skin peeling, skin redness, swelling due to fluid retention, vaginal discharge, vaginal inflammation, vomiting, yellow skin and eyes.


Inform your doctor before combining Keflex with:

diarrhea medications such as Lomotil, oral contraceptives.

No known food/other substance interactions.

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Appears in breast milk; could affect a nursing infant.

No special precautions apply to seniors.

Follow doctor’s instructions carefully for children.

  • May cause false results in tests for sugar in the urine. Inform your doctor that you are taking Keflex. Do not alter your diet or dosage of diabetes medications without instructions from your doctor.
  • Inform your doctor before Keflex therapy if allergic to penicillin or cephalosporin antibiotics in any form, or if you have any drug allergies. Allergic reaction can be extremely severe.
  • Tell your doctor before starting the medication if you have a history of stomach or intestinal disease, especially colitis; or kidney disorder.
  • Consult with your doctor before using diarrhea medications; some interact with Keflex.
  • If used on a long-term basis, may cause a secondary infection not treatable with Keflex.
  • Inform your doctor if symptoms do not improve within a few days or get worse.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Keflex side effects, please contact your healthcare provider.