Cephalexin (Oral)

Cephalexin is a medication that is used to treat bacterial infection throughout the body and belongs to the class of cephalosporin antibiotics.


Cephalexin is a cephalosporin that is used to treat gram-positive bacterial infections and is taken in either tablet or capsule (oral) form. It is only available through prescription and is known by the brand names Bio-Cef, Keflex and
Panixine DisperDose in the US. This drug is used to treat conditions such as urinary tract infections, ear infections, and skin infections. This medication poses a risk for an allergic reaction and should not be taken by individuals who are allergic to Cefzil, Omincer or penicillins. This medication works much in the same way that penicillin does, so it is not a safe treatment for people with a penicillin allergy.

When taking this medication, you may begin to feel better but should continue to take all of your prescriptions. Do not take more of this drug than is prescribed by your doctor. If you miss your regular dose, you should take it as soon as you remember unless it is time for your next dose. Do not take two doses at once. If you take more than the prescribed amount, you may experience symptoms of overdose such as blood in your urine, vomiting, stomach pain, and diarrhea. Symptoms of an allergic reaction to this medication include swelling of the face, throat, tongue, and lips. You may also experience hives and difficulty breathing.

You may take this medication with or without food. You should take your medication with a full glass of water and ensure that your keep hydrated to help reduce the risk of side effects. If you have a condition such as renal impairment, liver disease, or diabetes, you should consult with your doctor to determine what type of dose you may be able to tolerate. People with these conditions are more susceptible to experience dangerous side effects and a decline in their preexisting condition.

You should be monitored closely by your health care provider when taking this medication. If there are any sudden changes in your condition or side effects you should report them to your doctor. Experiencing persistent diarrhea, fever, chills, and pain in the stomach or side can indicate a serious issue with this medication. Seek medical attention for any serious side effects that develop as a result of taking cephalexin.

Keep this medication out of the reach of children and pets. Always travel with your prescription in the bottle it came in. Keep this drug away from heat, light, and humidity. Do not change your prescribed dose and do not store other medication with cephalexin. If anyone under the age of 18 is prescribed this medication, there is likely to be a dose adjustment for age. The dose of this medication is dependent on the particular condition of the patient, their age, and the nature of the infection to be treated. This medication is only intended to treat bacterial infection and not viral infections.

Do not stop taking this medication once you begin to feel better. Take the prescription exactly as directed and complete your course of antibiotics. Once you begin treatment with cephalexin, it may take up to 48 hours for you to notice a decrease in your symptoms. If you are pregnant or nursing, you should tell your doctor before you begin treatment with this medication. It may be dangerous for your fetus and is not recommended for breastfeeding mothers.

Conditions treated

  • Bacterial infection

Type of medicine

  • Antibiotic

Side effects

This medication has been known to cause a variety of side effects ranging from mild to severe. Always tell your doctor about any other medications you are taking to lessen the chance of interaction and side effects. Only take this medication as directed in the prescribed dose. Only take a single dose of this medication at one time. If you develop side effects tell your doctor or seek emergency medical help.

Common side effects

  • Diarrhea

Diarrhea is a common side effect but should be reported because it could indicate the development of a secondary infection that may need medical treatment.

Rare side effect

  • Stomach or abdominal pain

If you experience either abdominal pain or stomach pain, you may have a secondary infection, or you may be having problems tolerating this medication. Ask what your options are; if you do not have a developing infection it may be a sign of Clostridium difficile.

  • Loosening of the skin

This is a rare condition that may be a direct result of this medication and would normally require a change in your treatment plan.

  • Blistering or peeling of the skin

Any blistering or peeling of the skin as a result of cephalexin should be immediately addressed by your health care provider. It is a sign that you are not tolerating your treatment well.

  • Cough

A cough may be a sign of an underlying issue that may need immediate medical treatment. Monitor your condition and report any sudden changes.

  • Clay-colored stools

You should monitor any clay-colored stools to report to your doctor or health care provider as a precaution.

  • Diarrhea

Although diarrhea can be a common side effect, continuous or ongoing diarrhea can be the sign of a serious condition.

  • Dark urine

Monitor your urine output and report any dark or unusual coloring to your health care provider.

  • Fever

If you continue to run a fever or have a high fever, you should get medical attention.

  • Dizziness

Some individuals may experience dizziness during the adjustment phase. If this side effect persists, you may need to get a dose adjustment or find an alternative treatment.

  • Fatigue

You may notice an increase in fatigue when taking this medication. If this condition persists or suddenly worsens you may not tolerate the medication well.

  • Rash or itching

Any unusual rashes or itching could be the sign of an allergic reaction.

  • Muscle or joint pain

Muscle and joint pain is uncommon and should be monitored closely, especially if they accompany other side effects.

  • Unusual stool color

Report any unusual stool color to your health care provider because it could indicate an underlying issue.

  • Appetite loss

Some people who take cephalexin may notice a decrease in appetite, especially during the initial treatment. If the condition persists you should ask what your other treatment option is.

  • Vomiting or nausea

Nausea and vomiting can be a sign of intolerance to the medication. It can also be a sign of a developing infection.

  • Skin Lesions

Skin lesions are rare when taking cephalexin. They may be a sign of intolerance or an allergic reaction to the treatment.

  • Irritated, red eyes

In some rare instance, you may experience red, dry eyes. Ask your health care provider what you can do to help relieve this side effect.

  • Sore throat

If you develop a sore throat while taking this medication, you may be developing a secondary infection, or you may have an adverse reaction to this treatment. Ask what your treatment alternatives are if you do not tolerate this medication well.

  • Ulcers with white spots on mouth and lips

Any development of an ulcer with white spots on the mouth is a serious condition that requires medical treatment.

  • Bad breath

Although bad breath is a rare side effect of this medication, it is possible. Make sure you drink plenty of water with cephalexin to help decrease the occurrence of this minor but rare side effect.

  • Tiredness or weakness

Some individuals experience tiredness or weakness when they begin this medication. If the condition persists or changes suddenly, you should seek medical assistance.

  • Vomiting blood

Vomiting blood is a rare and very serious side effects. Seek emergency medical attention right away if you experience this side effect.

  • Yellowing of eyes or skin

Yellowing of the skin or eyes can be a sign of renal failure and should be treated by your healthcare provider right away.


Cephalexin should be administered orally for adults. The available doses of this medication are 250 mg and 500 mg. The dose for each specific condition varies and is determined by your attending physician at the time he prescribes the medication. If you are having trouble adjusting to your medication, you may need to have your dose adjusted if possible. Due to the effects of some pre-existing medical conditions, there are certain dose adjustments to take into consideration.


There are a total of 47 known drug interactions associated with cephalexin. Of these 47 drugs, there is 1 major drug interaction, 4 moderate drug interactions, and 2 minor drug interactions.The most common drug that interacts with cephalexin is lasix.

Disease interactions:

  • Renal dysfunction

Individuals with renal dysfunction may require a dose adjustment.

  • Liver disease

Patients with hepatic disease should be monitored closely for developing issues while taking cephalexin.

  • Colitis

Colitis can develop in patients who are taking this medication and can last for up to two months.

  • Seizure disorder

Patients who have a renal disorder in conjunction with seizure disorder are more likely to have additional seizures when taking this medication.


Do not take this medication if you are allergic to Cefzil, Omincer or penicillins. If you develop trouble breathing or notice an unusual rash or even swelling in your face or tongue you should seek emergency medical assistance. An allergic reaction may also cause vomiting and diarrhea. If you have any medical conditions, you should tell your doctor before beginning this medication. If you notice persistent diarrhea, you may be developing a serious condition and should alert your healthcare provider right away.

Patients who have a renal impairment, liver disease, or who have diabetes are susceptible to a variety of dangerous side effects and issues. These patients may require a dose adjustment and should be monitored carefully throughout their therapy with cephalexin. Seek medical attention if you develop chills, fever, trouble breathing, or a general feeling of illness. If you are pregnant or nursing, you should inform your doctor before you begin taking this medication. It is not recommended that pregnant women or mothers who are breastfeeding should take this medication unless directed by their physician.

Do not take more of this medication than directed and be sure to finish the entire prescription even if you begin to feel better. Do not take this medication if it is expired. Expired medication should be disposed of properly. Individuals who are being treated with cephalexin should be monitored closely for any developing secondary infections or side effects. If you believe you are having a severe side effect or a life-threatening emergency, you should seek medical attention right away.


This medication should be stored in a lockable container away from heat and light. Do not store in areas such as the bathroom where it will be exposed to excessive moisture. If this medication expires, you should dispose of it right away. When disposing of this drug, you should take it to your local community take-back program. If you do not have a take-back program, you should consult the FDA's pamphlet regarding proper medication disposal. It is recommended that you keep your medication in the prescription bottle it came in, especially if you plan to travel. Do not store other medications with this medication. If this medication expires, you should throw it away and talk to your doctor if you feel you need additional medication.


Cephalexin is an antibiotic that is used to treat a wide variety of bacterial infections. It is not intended to treat viral infections, however. Some common infections that are treated with cephalexin include ear and urinary tract infections. This medication does pose a risk of an allergic reaction and is known to produce a variety of side effects. If you experience any severe side effects or develop persistent diarrhea or fever, you should seek medical attention right away.

Talk to your doctor before you begin treatment with cephalexin. Report all of your current medication including herbal supplements and vitamins. If you have any pre-existing medical conditions you should tell your doctor. Do not take more than one dose of this medication at one time and keep it safely out of the reach of pets and children. Do not store this medication in the bathroom or anywhere where it will be exposed to heat, light, or excessive moisture.

Last Reviewed:
December 24, 2017
Last Updated:
April 04, 2018
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