Cephalexin Side Effects, Upsides, Downsides & How it Works

Cephalexin is a cephalosporin antibiotic and is used to treat bacterial infections as well as skin infections, upper respiratory infections, urinary tract infections, and ear infections. It is available in the form of tablets, capsules, and in liquid form. Cephalexin works similarly to penicillin. It fights bacteria by slowing their growth and preventing the production of the bacterial cell wall. This exposes the bacteria to the external environment due to which they are unable to survive.


However, Cephalexin should not be used to treat viral infections including flu and cold. Also, misusing or taking Cephalexin unnecessarily can decrease its effectiveness.


Side effects

Cephalexin can treat bacterial infections like ear infections and skin infections, but it also has some side effects. Most of the side effects are minor and disappear as your body adjusts to the use of Cephalexin. However, seek immediate medical help if any of the minor side effects do not go away or worsen.

Minor side effects

  • Fever
  • Dizziness
  • Tiredness
  • Vaginal itching or discharge
  • Diarrhea
  • Skin rash
  • Headaches
  • Abnormal liver tests
  • Joint pain


However, some of the side effects are serious and can become life-threatening if not treated immediately. Visit your doctor if you experience any of the following major side effects.

Major side effects

  • Jaundice
  • Little to no urination
  • Diarrhea that is bloody or water
  • Agitation and hallucinations
  • Easy bruising and bleeding
  • Purple spots under your skin
  • Signs of a skin reaction including burning in your eyes, sore throat, blistering, fever, or swelling in your tongue or face.
  • Signs of an allergic reaction including dizziness, itching, trouble breathing, swelling, and rash


How to use?

Take Cephalexin only according to the prescribed dosage, without increasing or decreasing your dose. It is advisable to take Cephalexin every 6 to 12 hours unless prescribed otherwise by your doctor. You can take Cephalexin with food if you feel nauseous. Do not stop taking this medicine even if you feel well as this can increase the risk of further infection. Make sure you take Cephalexin for the prescribed time as it is possible that your symptoms go away even before your infection has cleared up. If you are using liquid Cephalexin, shake the bottle well. It is advisable to use a dose-measuring device to ensure you get the proper dose. Refrigerate the liquid medicine and do not take Cephalexin if it has been unused for 14 days. Store the capsules and tablets in a cool, dry place, away from the reach of children.



  • Do not take Cephalexin if you are allergic to any of the active or inactive ingredients found in it, or to penicillins and other cephalosporins. It is advisable to ask for a list of ingredients from your pharmacist to avoid a severe allergic reaction.
  • Inform your doctor of all the diseases you have had, especially if you have a history of kidney disease and stomach or intestinal disease.
  • Inform your doctor and dentist of all the medications you are taking before undergoing any surgery.
  • The liquid form of Cephalexin contains sugar; hence, use it with caution in people who have diabetes. Consult your doctor about the use of Cephalexin if you have diabetes.


  • It is not advisable to have vaccinations and immunizations while using Cephalexin as it can make the vaccine less effective.
  • It is uncertain whether Cephalexin can harm an unborn baby and should only be taken if necessary. Consult your doctor about the use of Cephalexin if you are pregnant.
  • Cephalexin can pass into breast milk and can have harmful effects on a nursing infant. Consult your doctor about the use of Cephalexin before breastfeeding.