7 facts about Cephalexin (Keflex) for UTI & 12 tips when treating UTI with antibiotics


Did your doc prescribe you Cephalexin for UTI? Read about my experience using Cephalexin for urinary tract infection treatment.

Also, make sure to scroll down to read 10 useful tips when treating UTI with antibiotics and learn how to help your body to recover from antibiotics.

7 facts about Cephalexin for UTI (KEFLEX)

To treat my UTIs physicians prescribed me at first Cephalexin (KEFLEX), and then for the second and all the following infections I used Nitrofurantoin (Macrobid). For the very last infection (2015) I was prescribed Cipro.

Cephalexin was approved by the FDA in January 1971. It slows or stops the growth of the bacteria cells, which bacteria need to survive. A couple of things to consider, when taking cephalexin for UTI:

  1. Cephalexin and Pregnancy

    There are no conclusive studies of using cephalexin in pregnant women. But from what we know so far, Cephalexin shown to be very effective and complications to mother and child are very rare.

  2. If you are allergic to penicillin you may also be allergic to cephalexin

    According to a study published in Journal of investigational allergology and clinical immunology, if you are allergic to penicillins you chances to be allergic to cephanexin are about 11%.

  3. Yeast infection and unhealthy vaginal flora

    As any other antibiotic it will kill your good bacteria and yeast infection is an almost guaranteed side effect.

    Unfortunately, once your good bacteria are depleted you are not only more prone to yeast infection, but also more vulnerable to your own E. coli bacteria.

  4. It could increase risk of repeated UTIs

    Cephalexin belongs to a category of cephalosporin antibiotics. I recently came across a study that demonstrated that another drug from cephalosporin group (Cephadroxil) promotes vaginal colonization with Escherichia coli. And this is exactly how UTI infection cycle starts!

    If your vagina is colonized with E. coli, you are almost guaranteed repeated UTIs after sex (get familiar with the mechanics of why sex causes UTIs if this sounds surprising).

  5. Other side effects of Cephalexin for UTI

    I personally didn’t have any complications besides the yeast infection, but top three concerns of the patients on Treato, when taking this drug are: allergies (most reported), thrush and nausea. Other possible side effects include:

    • diarrhea;
    • dizziness, feeling tired;
    • headache, joint pain;
    • vaginal itching or discharge.
  6. Cephalexin for UTI can lead to resistance with long-term use

    A systematic review of 15 studies, including 1644 women aged over 75 years, concluded that short courses of antibiotics (varying from 3 to 6 days, depending on the antibiotic chosen) are as effective as long courses (7–14 days) for treating uncomplicated cystitis in older women.

    The longer the duration of treatment, the higher your chances to develop an antibiotic resistant bacteria. However, do not shorten the prescribed course yourself and always consult with your prescribing physician.

  7. How soon it will work if you take Cephanexin for UTI?

    I felt almost immediate relief. You should definitely feel better within the first 8-12 hours but make sure to finish all pills regardless of how well you feel.

Follow these 12 tips when treating UTI with any antibiotics:

  1. Take them regularly

    You need to make sure to take one pill every 12 hours (unless prescribed otherwise) to support a constant level of antibiotics in your body. It is better to take the first pill sometime between 7-10 (a.m or p.m.).

    When treating my first UTI infection I took the first pill at 3 p.m. For the following 7 days I had to set my alarm for 3 a.m. in the morning to take my night dose. Not fun!

  2. Take them on time

    Once you take your first pill, set your phone timer for 12 hours. Repeat it every time you take a pill till you are done.

  3. Plan ahead

    Make sure to take your pills to work! For example, I separated mine in two containers so that I would always have some in my purse for the 3 p.m. pill and the rest would be by my bed for the 3 a.m. dose.

  4. Take all pills

    To clear up your infection completely, take antibiotics for the full course of treatment. Keep taking it even if you feel better in a few days.

    I had no symptoms just a few hours after the first pill. However, if you stop taking the antibiotics early you’ll increase your chances for a repeated infection and antibiotic resistance.

  5. Do not take extra

    If you forget and miss a dose, take the pill as soon as you remember. Skip the missed dose if it is almost time for your next one. Do not take extra medicine to make up for the missed dose.

  6. Stay sober

    It’s better to avoid alcohol. Sometimes it can worsen the side effects, sometimes it can affect the effectiveness of a drug. Because your liver is already under serious pressure to deal with the infection and the antibiotics, you do not want to overwhelm it with alcohol.

  7. Support your vaginal and bladder flora

    Start on a course of probiotics right away and plan for one more right after your treatment. Studies show that if you take probiotics while taking the antibiotics your beneficial flora will recover to it’s normal state faster and you are less likely to develop yeast infection.

    To summarize, wait couple hours if possible to take your probiotic pill, do not take it at the same time as antibiotics and take special probiotics for 30 more days after you are done.

  8. Revitalize your microbiome after

    Continue with more probiotics after you finish your course of antibiotics. Make sure to buy special kind of probiotics containing beneficial vaginal bacteria. This will help you to prevent infections in the future.

  9. Watch out for serious side effects

    Do read the potential side effect of the antibiotics that your physician prescribed you. Let your doctor know if you develop diarrhea or vomiting. Some antibiotics (doxycycline, tetracycline, ciprofloxacin, levofloxacin, ofloxacin, trimethoprimcould also make your skin sensitive to sun.

  10. Avoid Cipro

    If your doc prescribed you Cipro, ask him/her if you can start with an alternative option. Since 2016 FDA does not recommend prescribing Cipro for uncomplicated UTIs, but too many physicians just do what they are used to do. Make sure you are your own advocate!

  11. Take NAC supplements

If you are suffering from recurrent UTIs, it is critical to fight microbial biofilms. Take NAC supplements that could double the efficacy of the antibiotics to help you to destroy pathogenic bacteria.

If you want to try to prevent and treat UTI naturally read the post about D-Mannose and all the comments from other readers.There are some really interesting stories!

12. Take D-Mannose with antibiotics

Currently, there is no information about D-Mannose interaction with antibiotics or any other drugs. If you are considering to boost your antibiotic treatment, I’d give D-Mannose a try. After all, D-Mannose is simply a sugar.

What type of antibiotics you have tried? Leave me a comment, I’d love to hear from you.


  1. Using antibiotics responsibly: right drug, right time, right dose, right duration.
  2. Antibiotic duration for treating uncomplicated, symptomatic lower urinary tract infections in elderly women.
  3. Cephadroxil promotes vaginal colonization with Escherichia coli.
  4. Cross-reactivity and Tolerability of Cephalosporins in Patients With Cell-Mediated Allergy to Penicillins
  5. Treatments for symptomatic urinary tract infections during pregnancy


  1. Hi, I am 9 weeks’ pregnant. I was prescribed Cefalexin (Keflex) 500mg x3 daily. Unfortunately 7 days later I still have symptoms. I am now on Co-Amoxiclav x3 daily. Fingers crossed, but wouldn’t wish this misery on anyone. I haven’t slept for a week….

    • Hi Jaimie,
      I’m so sorry to hear! Wish you and your baby to get through this as quick as possible. Just FYI, when on antibiotics you can still add D–Mannose to your treatment to see if it can speed up the recovery. Make sure to follow your physician’s prescription and finish all the antibiotic pills.
      Hopefully you’ll be over the hump in no time! Plan to double down on the preventive measures once you are healthy!

  2. I am taking this for a UTI and wowser it is making me feel like a zombie.I feel so drained and no energy.I have 1 to go tonight and 1 twice a day for next two days.Any hints on when to take it to cause the least chaos to my day as i have to work and seriously dont think i will cope if i take them at work.Work is 9am-5pm.Anyone taken them just at night so no side effects during the day.

    • Hey Ana, sorry to hear you are not taking it well. One more day to go!
      Talk to your doc but I don’t think he would change anything right now. Unfortunately you have to take each pill 12 hours apart to support the level of the antibiotic in your blood, there is no way around that.
      Best wishes,

  3. will the itching inside stop after I finish my meds 🙁 its horrible
    I started taking Sunday its Tuesday now and have to take it 4 times a day for 3 days

    • Hey Nita!
      That’s an interesting side-effect, sorry must be annoying. Did you tell your doc? Try taking probiotics, see if this helps.

  4. Just started Cephalexin and I accidentally took the second pill 3 hours after taking the first one! Will this affect anything? How fast will it start working? Seems like it flared up my itching/urge instead of settling it down. Is it normal ?

    • Hi Pris,
      Sorry I left you hanging, it was my wedding weekend so I disconnected.
      1) IMHO (and I’m not a doctor to provide a medical advice, so ask your doc): Taking too much at short intervals is not the worst mistake. Personally, I wouldn’t worry about it, and would try to keep 12 hours intervals going forward.
      2) “How fast” is very individual, but for me it worked within 2 hours after the first pill. Hopefully already worked for you! If not, let your doc know.
      3) Depends on what is itching 🙁 Itching is not really a common symptom of a UTI, if you have itching it could be anything ranging from an STD to an allergic reaction. Do tell your doc!
      Best wishes and feel better soon,

  5. I was prescribed this on Aug 30 for UTI that had me unable to walk because of the pain in my back. I’m to take 2 every 12 hours. It took almost to day 6 to feel completely releived. I’ll finish the next 4 days. No side effects outside of very bad bloating. I’m using a probiotic that I’ll probably continue. Thanks for the very informative article.

    • Danielle, sounds like your infections spread to your kidneys and I’m glad to hear that you are feeling better. Make sure to choose right probiotics and see if you could take it for at least one month after you are done with the treatment. Best wishes,

    • There are many reasons why you could experience a UTI once again in such a short period of time. I’m curious to know what the results of the test. Best of luck,


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