Cephalexin

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Mar 12, 2024

Warnings

Cephalexin Risks, Warnings, and Complications

Cephalexin can cause or worsen health problems in some people. Talk to your doctor about other treatment options if you are at an increased risk of complications from this antibiotic. Some of the risks of cephalexin use include:

SEVERE ALLERGIC REACTIONS: In a small number of people, cephalexin can cause a severe drug reaction, including swelling of the face and throat, wheezing, trouble breathing, and anaphylaxis (throat closing). Before starting treatment, tell your healthcare provider if you have ever had hypersensitivity reactions to any antibiotics, including cephalosporins and beta-lactam antibiotics (penicillins). Up to 10% of patients with an allergy to penicillins also have an allergy to cephalosporin antibiotics. Seek emergency medical care if you develop a skin rash, hives, itching, swelling of the face, lips, tongue, throat, hands, or feet, wheezing, or difficulty breathing or swallowing.
CLOSTRIDIUM DIFFICILE-ASSOCIATED DIARRHEA: Cephalexin and other antibiotics can increase the risk of developing a severe type of diarrhea that is caused by a bacteria called Clostridium difficile or C. diff growing out of control. This can happen up to 2 months or more after antibiotic therapy. Call your doctor immediately if you develop fever, nausea, stomach cramps, stomach pain, and severe bloody, watery, or bad-smelling diarrhea.

Precautions Before Starting Cephalexin

Tell your doctor if you have had allergic reactions in the past to cephalexin, any of the active or inactive ingredients in cephalexin formulations, other cephalosporins, penicillin antibiotics, or any other drugs. Your pharmacy can give you a list of ingredients.

Examples of other cephalosporin antibiotics include cefazolin (Kefzol, Ancef), cefoxitin (Mefoxin), ceftriaxone (Rocephin), cefditoren (Spectranef), cefotaxime (Claforan), ceftazidime (Fortaz, Tazicef), cefuroxime (Zinacef), ceftaroline (Teflaro), cefixime (Suprax), ceftibuten (Cedax), cefepime (Maxipime), cefaclor, cefpodoxime, cefadroxil, cefdinir, cefotetan, cefixime, cefprozil, and cefotetan.

Give your doctor your complete medical history. Cephalexin may not be safe for people with certain health conditions, such as allergies, liver disease, kidney disease, and gastrointestinal conditions like colitis.

Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, vitamins, supplements, and herbal products. This can help avoid possible interactions between cephalexin and your other other medications.

Tell your doctor if you are pregnant, could be pregnant, are planning a pregnancy, or are breast-feeding (small amounts of the medicine may pass into breast milk).

Precautions During Use of Cephalexin

Keep all your medical and lab appointments while on cephalexin. Tell your healthcare provider if your symptoms do not improve, get worse, or go away, and then come back.

Cephalexin can interfere with the results of certain lab tests. If you have diabetes and check your urine for sugar, use TesTape or Clinistix (but not Clinitest). Tell all laboratory personnel that you are on cephalexin before any lab tests.

Tell your healthcare professional if you become pregnant while on cephalexin.

Cephalexin Drug Interactions

Taking cephalexin with certain other drugs can affect how the medicines work. Possible interactions between cephalexin and other medicines can increase the risk of serious adverse effects. Your doctor may change the dose of your medications, switch you to a different medication, or monitor you carefully for side effects if there are known interactions between cephalexin and your other medicines. Cephalexin can have drug interactions with the following medications:

Anticoagulants or blood thinners such as warfarin (Jantoven, Coumadin)
Diabetes medications such as metformin (Glucophage, Fortamet, Glumetza, Riomet, Invokamet, in Glucovance)
Medications used to treat gout, such as probenecid (Probalan)

Give your health care professional a complete list of all the medications you are taking, including prescription drugs, non-prescription medicines, dietary supplements, and herbal products. Also, tell your healthcare provider if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription and over-the-counter medicines.

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