Is Keflex the best antibiotic for urinary tract infection?

Cephalexin is an antibiotic in a class of drugs called cephalosporins. Cephalexin fights bacteria in the body.

Cephalexin is used to treat many different types of bacterial infections, such as bronchitis, tonsillitis, ear infections, skin infections, and urinary tract infections.

Cephalexin may also be used for purposes other than those listed in this medication guide.


  • Take this medication exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
  • Take each dose with a full glass of water.
  • Cephalexin can be taken on an empty stomach or with food or milk if it causes stomach upset.
  • To ensure that you get the correct dose, measure the liquid form of cephalexin with a dose-measuring spoon or cup, not a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist where you can get one. Shake the suspension well before measuring a dose.
  • Take cephalexin at evenly spaced intervals to maintain a constant level of the drug in the body.
  • It is important to take cephalexin regularly to get the most benefit.
  • Take all of the cephalexin that has been prescribed for you, even if you begin to feel better. Your symptoms may start to improve before the infection is completely treated.
  • Keep the Keflex tablets and capsules at room temperature away from moisture and heat.
  • Store the suspension in the refrigerator. Throw away any unused medication after 14 days.

Side Effects

If you experience any of the following serious side effects, stop taking cephalexin and seek emergency medical attention or contact your doctor immediately:

  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, face, or tongue; hives; or a rash);
  • rash, redness, or itching;
  • severe nausea, vomiting, or diarrhea;
  • mucous or blood in the stool; or
  • unusual bleeding or bruising.

Other, less serious side effects may be more likely to occur. Continue to take cephalexin and talk to your doctor if you experience any discomfort.

  • mild nausea or diarrhea, or
  • a yeast infection of the mouth or vagina.

Other side effects other than those listed here may also occur. Talk to your doctor about any side effects that seem unusual or that are especially bothersome.


Before taking CEPHALEXIN, tell your doctor if you have any allergies (including penicillins, cephalosporins, or any other drug), or kidney disease. Use of CEPHALEXIN for prolonged or repeated periods may result in a secondary infection (e.g., oral, bladder, or vaginal yeast infection). CEPHALEXIN should be used only if clearly needed during pregnancy. It is not known if CEPHALEXIN is found in breast milk; consult your doctor before breast-feeding.

Drug Interactions

Tell your doctor about all prescription and nonprescription drugs you may use, especially drugs used for gout, such as probenecid. CEPHALEXIN may interfere with the effectiveness of birth control pills. Discuss using other methods of birth control with your doctor. CEPHALEXIN may cause false positive results in tests for sugar in the urine. Diabetics should use TesTape rather than Clinitest tablets to test for sugar while using CEPHALEXIN. Do not start or stop any medicine without doctor or pharmacist approval.

Missed Dosage

Take the missed dose as soon as you remember, then try to evenly space the rest of the doses for that day until you can return to a normal schedule. Do not take a double dose of this medication unless otherwise directed by your doctor.


Follow label warnings about whether or not to refrigerate. Do not freeze. Do not store in the bathroom. Discard any unused portion after 14 days because the drug loses potency.

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