Cefalexin (Cephalexin)

Cefalexin (Cephalexin)

Cefalexin is a relatively common form of antibiotic used for the treatment of infections caused by bacteria in the body. This medication will not treat viral infections like the common cold or the flu. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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Cefalexin, sometimes spelled Cephalexin, is a kind of antibiotic known as a cephalosporin. This is a type of broad-spectrum antibiotic that is used to treat infections caused by bacteria. You can only get Cefalexin with a prescription.  

What is Cefalexin? 

Cefalexin is a relatively common form of antibiotic used for the treatment of infections caused by bacteria in the body. This medication will not treat viral infections like the common cold or the flu. Cefalexin is a kind of antibiotic commonly referred to as a cephalosporin, it works by killing the pathogenic bacteria in the body that is responsible for your infections.  

Cefalexin can be given for a wide range of ailments, but it is only available on prescription, and should not be taken without medical advice.  

When is Cefalexin used? 

Cefalexin is a broad-spectrum antibiotic, which means that it works well against a wide selection of germs and bacteria. This medication can treat a host of commonly occurring infections, including infections of the urinary tract, skin, throat, and chest. In some cases, it may also be used for ear infections, throat infections, and dental issues.  

Cefalexin may be given for the treatment of pneumonia and tonsillitis, or laryngitis in certain cases, however your doctor will need to conduct a full assessment to determine whether your ailments are susceptible to treatment with Cefalexin. Using an antibiotic of any kind when it is not definitely needed could mean that this medication does not work for you in the future when you need it most.  

Cefalexin may not be suitable for some people who are allergic to penicillin antibiotics, as it is based on the penicillin drug. When taken properly, this medication will both help to get rid of the underlying infection causing your symptoms, and the side effects of that infection, such as fever and pain. 

How do you use Cefalexin? 

Medications like Cefalexin will come with a patient leaflet included in the packaging that provides you with plenty of information on how to safely take the drug and avoid any dangerous side effects. It is important to follow the instructions provided in these patient leaflets carefully, as they will give you the answers to any questions you might have about the medication.  

Cefalexin will be given a number of times each day, to help build up a certain amount of the medication in your system. Your doctor or consultant may be able to advise you on the right dose for your condition. It is important to take Cefalexin according to the instructions provided to you, and at a regular time every day for the full course of your treatment. Some people may be given Cefalexin as a strategy to prevent against recurring urinary tract infections. If this is the case, then you will likely only need to take a single dose of the medication once per day.  

Cefalexin can be taken either with, before, or after food. Some people find that the medication does start to work a lot faster on an empty stomach, however. You should check with your doctor to ensure that you should not be taking Cefalexin at a certain time each day. Spacing the doses evenly throughout the day will help you to get the right dose in your system at all times.  

If you forget to take a dose of Cefalexin, make sure that you take it when you remember, unless you know that it is time for your next dose soon.  

Continue to take Cefalexin at the appropriate times each day for the full course as prescribed as your doctor. Stopping your consumption of an antibiotic too early could increase your chances of the infection coming back and becoming resistant to the antibiotic. This may require a more dangerous form of treatment.  

If you are taking the oral suspension form of this antibiotic, make sure that you shake the bottle well before use, and use only the measuring device given to you.  

What dosages are there? 

When given in pill form, Cefalexin usually comes in doses of 250mg and 500mg depending on the condition that you need to be treated. The dosage you get will often come every six to twelve hours, and your doctor will tell you how much you need to take based on your condition.  

The most common dose is one 250mg or one 500mg capsule taken four times per day. You should not take more than 4 grams of Cefalexin in a single 24 hour period. Adjusted doses may be given to children under the age of eighteen years.  

For the best effect from this medication, try to take it at evenly spaced times throughout the day. It can be helpful to set alarms to help you remember, or to take the medication at the same time every day 

What are the side effects of Cefalexin? 

Many doctors and medical experts consider Cefalexin to be a relatively safe form of antibiotic for the treatment of a wide range of infections. However, like all medications, it is possible that you might suffer from side effects when taking this substance.  

Crucially, it is important to remember that different people get different side effects to medications like Cefalexin Sometimes, upset stomach, vomiting, diarrhea or nausea may occur. If any of these effects worsen or persist, then you should seek doctor’s advice. However, they may go away on their own as you get used to the medication.  

Use of this medication for an extended period of time could result in a new yeast infection or a case of oral thrush. If that happens, then you should contact your doctor. Watch for any signs of a change in vaginal discharge, white patches in your mouth, or other new symptoms. 

In very rare circumstances, this medication could cause a severe reaction in your intestines. This happens because of a resistant bacteria in your system. Clostridium diarrhea is a possible problem with many antibiotics, and it can happen long after you have stopped your treatment. If you notice any persistent diarrhea that doesn’t go away, or stool with blood and mucus in it, then you should speak to your doctor immediately.  

If you are having symptoms that include diarrhea, do not take any drugs that are designed to reduce this problem, as they could make the issue worse.  

An allergic reaction to Cefalexin is rare, but it can be more common if you are sensitive to penicillin. Make sure that you get medical help immediately if you recognize the signs of any allergic reaction, including itching or swelling around the tongue, face or throat, or problems with your breathing.  

When shouldn’t you use Cefalexin? 

Although Cefalexin is a wide-spectrum antibiotic that will work for a lot of different people, it will not be suitable for everyone. You should make sure that you answer all of the questions asked by your consultant carefully and truthfully when taking Cefalexin to make sure that it is safe for you to take. For instance, make sure that your consultant or doctor is aware of whether you have: 

  • Ever had allergic reactions to Cefalexin or any other medications. You should make sure that your consultant is aware of any reactions that you have had to penicillin or cephalosporin based medications in the past 
  • Problems in the way that your kidneys work, or any family history of problems with kidney failure and kidney disease.  
  • A chance of being pregnant, or if you are trying for a baby or feeding your child with breastfeeding. Currently, Cefalexin is not known to be particularly harmful to babies, but your doctor will advise you if you should take this. 
  • If you are using other medications that are similar to Cefalexin.  
  • If you take Cefalexin for several days and you do not see any improvements to your condition, then you may be resistant to the antibiotic and need a different treatment for the bacteria in your system. To make sure that you are getting the right treatment, your doctor might take samples of urine or saliva before you are given treatment.  

Does Cefalexin interact with other medications? 

Reading the patient leaflet that comes with your medication will give you a better idea of whether it is safe for you to take this drug with other substances. It is important to remember that drug interactions can be dangerous and should be taken seriously. You should always tell your consultant or doctor before you begin using Cefalexin if you are taking any other medications. This includes medications that you aren’t getting on prescription, or herbal remedies.  

Cefalexin may interfere with certain tests conducted by a doctor in the lab, including urine glucose tests. This could mean that you end up with false test results. Make sure that you tell your doctor or consultant before you take any tests when using Cefalexin  

Do not take Cefalexin with other medications that contain the same active ingredients, as this could increase your risk of side effects or an overdose.  

Where can you buy Cefalexin? 

Like all antibiotics your doctor will need to assess your clinical need, if cefalexin is advised then it is available to buy online through one of our partner pharmacies. However it is only available with a prescription, please proceed to fill in an online consultation. 

Can I get Cefalexin without a prescription? 

Like many antibiotics, Cefalexin is only available on prescription.  


BNF Nice, online, 2020, “CEFALEXIN”[Accessed 15th of February 2020], Available on: https://bnf.nice.org.uk/drug/cefalexin.html 

Medicines.org, online, 2020, “Cefalexin 250mg Capsules” [Accessed 15th of February 2020], Available on: https://www.medicines.org.uk/emc/product/2814/smpc 

Patient Info, 2020, online, “Cefalexin for infection”  [Accessed 15th of February 2020], Available on: https://patient.info/medicine/cefalexin-for-infection-keflex 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.