Keflex is an antibiotic and treats infection. Finish taking all of your medication. Even if you feel better, do not stop taking medication unless your doctor tells you to stop.

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Keflex Overview


Keflex is a prescription medication used to treat bacterial infections. Keflex belongs to a group of drugs called cephalosporin antibiotics, which kill the bacteria that lead to infections.

This medication comes in oral (by mouth) capsule form. Keflex is taken up to 4 times a day with or without meals.

Common side effects of Keflex include upset stomach, diarrhea, and vomiting.

Patient Ratings for Keflex

How was your experience with Keflex?

First, a little about yourself

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What tips would you provide a friend before taking Keflex?

What are you taking Keflex for?

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  • Other
  • Bacterial Infections
  • Bites, Human
  • Endocarditis, Bacterial
  • Escherichia Coli Infections
  • Klebsiella Infections
  • Pharyngitis
  • Pneumonia, Bacterial
  • Proteus Infections
  • Skin Diseases, Bacterial
  • Soft Tissue Infections
  • Staphylococcal Infections
  • Streptococcal Infections
  • Surgical Wound Infection
  • Urinary Tract Infections

How long have you been taking it?

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  • Less than a week
  • A couple weeks
  • A month or so
  • A few months
  • A year or so
  • Two years or more

How well did Keflex work for you?

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How likely would you be to recommend Keflex to a friend?

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Keflex Cautionary Labels


Uses of Keflex

Keflex is a prescription medication used to treat certain bacterial infections. Keflex treats bacterial infections of the lung (pneumonia), ear, skin, bone, and urinary tract. 

Keflex and other antibiotics will not treat viral infections such as the flu or the common cold.

This medication may be prescribed for other uses.  Ask your doctor or pharmacist for more information.


Keflex Drug Class

Keflex is part of the drug class:

Side Effects of Keflex

Common side effects of Keflex include:

  • upset stomach
  • diarrhea
  • vomiting
  • stomach cramps
  • fever
  • mild skin rash

This is not a complete list of Keflex side effects. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with Keflex . See “Drug Precautions” section.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Keflex Interactions

Tell your doctor about all the medications you take including prescription and non-prescription medications, vitamins, and herbal supplements. Especially tell your doctor if you take:

  • metformin (Glucophage)
  • probenecid (Benemid)

This is not a complete list of Keflex drug interactions.  Ask your doctor or pharmacist for more information.

Keflex Precautions

Serious side effects have been reported with Keflex including:

Hypersensitivity reaction:  An allergic reaction is possible with Keflex .  Tell your doctor if you are allergic to penicillin antibiotics such as amoxicillin (Moxatag) and ampicillin or cephalosporin antibiotics such as cephalexin (Keflex) and cefuroxime (Ceftin). Symptoms of an allergic reaction to Keflex include:

  • skin rash
  • itching
  • hives
  • difficulty breathing or swallowing
  • sore throat
  • vaginal infections
  • dizziness
  • fatigue
  • headache
  • agitation
  • confusion
  • hallucinations
  • joint pain

Clostridium difficile associated diarrhea:  Keflex and other antibiotics can kill the “good” bacteria in the colon leading to a growth of C. difficile bacteria.  C. difficile is “bad” bacteria that can cause diarrhea.

Seizures associated with patients having poor kidney function

Keflex Food Interactions

Medicines can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods.  In the case of Keflex there are no specific foods that you must exclude from your diet when receiving Keflex.


Inform MD

Before taking Keflex, tell your doctor about all your medical conditions.  Especially tell your doctor if you:

  • have had an allergic reaction to Keflex, or other cephalosporins
  • have had an allergic reaction to penicillin antibiotics
  • have decreased kidney function
  • have decreased liver function
  • have a history of gastrointestinal (digestive tract) diseases
  • have been treated with anticoagulant therapies, or blood thinners
  • are pregnant or breastfeeding

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Keflex and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Keflex falls into category B.  Studies in animals have failed to demonstrate a risk to the unborn baby and there are no well-controlled studies in pregnant women.


Keflex and Lactation

Tell your doctor if you are breastfeeding or plan to breastfeed.  The active ingredient of Keflex is excreted in human breast milk.  The effect of Keflex on the nursing infant is not known.


Keflex Usage

  • Take Keflex exactly as prescribed.  Do not change the dose or stop taking Keflex without talking to your doctor. 
  • This medication comes in tablet, capsule, and oral suspension (liquid) forms. 
  • Keflex is typically taken 2 to 4 times a day for 7 to 14 days, with or without meals.
  • You should finish the entire course of treatment of the antibiotic to ensure your infection is treated appropriately.  It is important not to skip doses of Keflex.
  • Keflex can be taken with or without food.  Food or milk can prevent Keflex from causing an upset stomach.
  • Keflex tablets and capsules should be swallowed whole, not chewed, crushed, or split.
  • Keflex oral suspension should be shaken prior to taking the medication.
  • If you are diabetic, Clinitest urine glucose tests may give false results while taking Keflex.
  • If you miss a dose, take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of Keflex at the same time.

Keflex Dosage

Take Keflex exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

Your doctor will determine the appropriate dosage and schedule of Keflex depending on the type and severity of your bacterial infection, as well as your age.  For most infections, 250 mg of Keflex will be taken 4 times a day.  For more severe infections, 500 mg of Keflex will be taken twice a day.  The usual dosage range of Keflex is 1 to 4 grams a day, with a maximum dosage of 4 grams a day.

Keflex Overdose

If you take too much Keflex, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.


Other Requirements

  • Store Keflex oral suspension in the refrigerator for up to 14 days.
  • Store Keflex tablets and capsules at room temperature between 68° and 77°F (20° and 25°C).
  • Keep this and all medicines out of the reach of children.