Keflex Side Effects

Generic name: cephalexin

Medically reviewed by Drugs.com. Last updated on Oct 1, 2024.

Note: This document provides detailed information about Keflex.

Applies to cephalexin: oral capsule, oral powder for suspension, oral tablet Side Effects associated with cephalexin. Some dosage forms listed on this page may not apply specifically to the brand name Keflex.

Applies to cephalexin: oral capsule, oral powder for suspension, oral tablet.

Precautions

If your symptoms do not improve within a few days, or if they become worse, check with your doctor.

Serious allergic reactions can occur with this medicine. Check with your doctor right away if you have chest pain, blistering, peeling, or loose skin, red skin lesions, large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs, severe acne or skin rash, sores or ulcers on the skin, trouble breathing or swallowing, or fever or chills while you are using this medicine.

Cephalexin may cause diarrhea, and in some cases it can be severe. Do not take any medicine or give medicine to your child to treat diarrhea without first checking with your doctor. Diarrhea medicines may make the diarrhea worse or make it last longer. If you have any questions about this or if mild diarrhea continues or gets worse, check with your doctor.

Before you or your child have any medical tests, tell the medical doctor in charge that you are using this medicine. The results of some tests may be affected by this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of Keflex

Along with its needed effects, cephalexin (the active ingredient contained in Keflex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking cephalexin:

Other side effects of Keflex

Some side effects of cephalexin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to cephalexin: oral capsule, oral powder for reconstitution, oral tablet, oral tablet dispersible.

General adverse events

The most commonly reported side effects included diarrhea, dyspepsia, gastritis, nausea, and vomiting.^[Ref]

Gastrointestinal

• Frequency not reported: Diarrhea, nausea, vomiting, dyspepsia, gastritis, abdominal pain, anal pruritus, Clostridium difficile-associated diarrhea/colitis/pseudomembranous colitis
• Postmarketing reports: Colitis^[Ref]

Hematologic

• Frequency not reported: Direct Coombs' test seroconversion, decreased prothrombin activity/prolonged prothrombin time, eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia
• Postmarketing reports: Aplastic anemia, pancytopenia, leukopenia, agranulocytosis^[Ref]

Dermatologic

• Frequency not reported: Urticaria, rash, erythema multiforme, Stevens Johnson syndrome, toxic epidermal necrolysis/exanthematic necrolysis^[Ref]

Hepatic

• Frequency not reported: Transient hepatitis, cholestatic jaundice, AST and ALT elevations
• Postmarketing reports: Increased bilirubin^[Ref]

Hypersensitivity

• Frequency not reported: Hypersensitivity/allergic reactions, angioedema, anaphylaxis^[Ref]

Allergic reactions (including urticaria and angioedema) usually subsided upon treatment discontinuation.^[Ref]

Genitourinary

• Frequency not reported: Genital pruritus, genital candidiasis, vulvovaginitis/vaginitis and vaginal discharge^[Ref]

Nervous system

• Frequency not reported: Seizure, dizziness, headache^[Ref]

Psychiatric

• Frequency not reported: Agitation, confusion, hallucinations^[Ref]

Musculoskeletal

• Frequency not reported: Arthralgia, arthritis, joint disorder^[Ref]

Renal

• Frequency not reported: Reversible interstitial nephritis
• Postmarketing reports: Renal dysfunction, toxic nephropathy, increased blood urea nitrogen, increased creatinine^[Ref]

Other

• Frequency not reported: Fatigue
• Postmarketing reports: Fever^[Ref]

Immunologic

• Frequency not reported: Development of drug-resistant bacteria development^[Ref]

Metabolic

• Postmarketing reports: Increased alkaline phosphatase, increased lactate dehydrogenase (LDH)^[Ref]

Cardiovascular

• Postmarketing reports: Hemorrhage^[Ref]

See also:

Frequently asked questions

• What are the best antibiotics for a tooth infection?
• What is the best antibiotic to treat strep throat?
• Is Cephalexin safe for dogs? Uses, dosage, side effects?
• Can Cephalexin treat an abscess in the mouth or gum infection?
• If people are allergic to amoxicillin can they take cephalexin?
• Can you take cephalexin for a spider bite?
• Can you take antibiotics while pregnant?
• Cephalexin - is this a drug that can be abused by teens?

Further information

Keflex side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer