Some of the most common side effects associated with cephalexin include:
- Stomach pain
- Rectal or genital itching
- Dizziness or confusion
- Extreme tiredness
- Joint pain
This is not a complete list of adverse effects – though these are among the most common. Seek medical attention right away if you experience the following symptoms or other signs of infection while taking cephalexin:
- Skin rash
- Watery or bloody stools, stomach cramps, or fever during treatment or for up to two or more months after stopping treatment
- Swelling of the face, throat, tongue, lips, and eyes
- Difficulty breathing or swallowing
- A return of fever, sore throat, chills, or other signs of infection
- Hallucinations (seeing things or hearing voices that do not exist
Cephalexin can impact the readings of certain blood sugar tests for diabetes, so be sure to use Clinistix or TesTape (not Clinitest) during urine tests.
As with all prescription medication, be sure to inform the prescribing doctor about any medical conditions you have been previously diagnosed with, as well as any medication/ supplements you are currently taking before starting treatment with cephalexin.
Cephalexin can interact with other forms of medication and substances, causing potentially life-threatening side effects or serious allergic reactions. Be sure to let your doctor know if you’re taking any other cephalosporin antibiotics such as cefaclor (Ceclor), cefadroxil cefazolin (Ancef, Kefzol), cefdinir, cefditoren (Spectracef), cefepime (Maxipime), cefotaxime (Claforan), cefotetan, cefoxitin (Mefoxin), cefpodoxime, cefprozil, ceftaroline (Teflaro), ceftazidime (Fortaz, Tazicef, in Avycaz), ceftibuten (Cedax), ceftriaxone (Rocephin), cefuroxime (Zinacef), or cefixime, as these drug interactions may impact your treatment’s effectiveness.
You should also let your doctor know if you are taking any anticoagulants ('blood thinners') such as warfarin (Coumadin, Jantoven), or carbamazepine (Carbatrol, Epito, Equetro, Tegretol, Teril), as these medications can interact with cephalexin and cause potentially dangerous or life-threatening side effects.
In addition, let your doctor know if you are pregnant or plan on becoming pregnant before starting treatment with this medication.