9 Facts About Cephalexin (Keflex) For UTI & 12 Tips For Treating UTI With Antibiotics

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Written by Anastasia Visotsky,

Personally, I have taken Cephalexin to treat my UTIs twice; sat other times I was prescribed Macrobid and Cipro. To be frank, I tolerate antibiotics very well, but this doesn’t mean that I like them. Unfortunately, antibiotics are sometimes a necessary evil.

Here are some of my tips for successfully taking antibiotics for your UTI.

First of all, make sure that antibiotics are the right choice for you. If you only have bladder pain and it burns during or after urination but your urine is clear, antibiotics might not be the best solution. In fact, if you keep having UTIs, you might need to dig a little deeper (here are 25 most common UTI causes) to address the root cause of your UTIs, rather than simply repeating the cycle of antibiotic treatment.

If you see blood in your urine, it’s cloudy or has a strange smell, it may be time for antibiotics. Also, if you have fever or chills, pain in your flank and are not able to keep anything down, it’s really time to see your doctor.

Cephalexin (KEFLEX) & UTI: My Experience

I had my share of UTIs several years ago. Fortunately, I was able to get rid of this chronic problem, mostly by relying on a specific type of probiotics and some lifestyle changes.

If this is your first UTI and you are treating it with Cephalexin, there is no guarantee that the UTI won’t come back.

Remember, the antibiotics will kill the bacteria that invaded your bladder, but antibiotics will not address any of the underlying health conditions that may have caused the UTI in the first place.

If you do not want to experience the horrors of UTI again, make sure to implement smart prevention strategies, and do not rely solely on the antibiotics. Here are some tips to get you started:

Cephalexin For UTI: How Soon It’ll Work

By the time you take your first antibiotic pill, you are probably desperate for relief and are wondering how long it will take the Cephalexin will work.

It should work pretty quickly.

I felt almost immediate relief when taking Cephalexin for my UTI symptoms.

  • Within an hour of taking the first pill, the pain with urination subsided.
  • In a few hours, I no longer had blood in my urine.
  • By the next day, all my symptoms were completely gone.

Important: just because your symptoms are gone, don’t stop taking the Cephalexin early. While it may have killed enough bacteria to stop your symptoms, you run the risk of growing bacteria that can survive Cephalexin, or in other words drug-resistant bacteria.

Can you boost Cephalexin performance?

However, if you truly want Cephalexin to work, make sure to boost the performance of antibiotics with bacterial biofilm enzymes and a diet that keeps your urine alkaline.

Haven’t heard about bacterial biofilms? In a nutshell, the bacteria group together on the surface of your bladder and release “slime” to protect themselves from antibiotics.

What to expect when taking Cephalexin?

  • Once you start taking antibiotics, you should feel better within the first 8-12 hours. However, make sure to finish all pills regardless of how well you feel.
  • If you are not feeling better or if your symptoms are getting worse, if you start having any flank pain, or feel nausea and weakness, call your doctor.
  • Cephalexin might not work if you have a type of bacteria that are resistant to this antibiotic. However, in some cases, resistance could be mistaken with bacterial biofilms.

Cephalexin Could Increase The Risk Of Repeated UTIs

Cephalexin belongs to a category of antibiotics called cephalosporins.

I recently came across a study that demonstrated that another drug from the cephalosporin group (Cephadroxil) promotes vaginal colonization with Escherichia coli (or E. coli), the number one bacteria causing UTIs.

The study looked at monkeys and the antibiotic was placed directly into the vagina (not given by mouth). While another study shows that low dose daily cephalexin does not affect the vaginal flora, it is definitely possible that if you take full dose Cephalexin regularly, this e may have a detrimental effect on the vaginal microbiome.

Unfortunately, if your vagina is colonized with E. coli, you are almost guaranteed to have repeated UTIs after sex.

Healthy vaginas normally have the ability to deter E. coli bacteria and therefore play a key role in preventing UTIs. If your vaginal health is compromised, your risk of chronic UTIs is higher.

Cephalexin Could Promote Yeast Infection

Beneficial bacteria Lactobacilli are present in healthy vaginas and help to maintain an acidic pH that deters pathogens and yeast.

Like any other antibiotic, taking full dose Cephalexin regularly can deplete your good bacteria and yeast infection may be a side effect.

Unfortunately, once your good bacteria are depleted, you are not only more likely to get a yeast infection but also more vulnerable to infection from your own E. coli. This, in turn, could lead to recurrent UTIs.

Cephalexin For Chronic UTI

If this is not your first UTI, know one thing: you may not be fighting single-celled free-floating bacteria in your bladder. Most likely, you are fighting bacterial biofilms.

Cephalexin stops the growth of the cell wall, which bacteria need to survive. However, bacteria eventually learn how to hide from the antibiotic attack, allowing them to become resistant to Cephalexin.

One method is for them to team up, cover themselves with a protective “slime,” and hide in the deeper layers of your bladder lining. This allows bacteria to wait until you stop taking antibiotics before renewing their activity.

This bacterial method of defense is called “bacterial biofilms”.

Your UTI-like Symptoms after Cephalexin

There are two main scenarios that could explain why you still feel some or all of the UTI-like symptoms after taking antibiotics.

First, you could be resistant to this particular antibiotics. Second, it may not have been a UTI. Obviously, it is critical to differentiate between these two options.

Here is my in-depth interview with urologist Dr. Lisa Hawes explaining the difference between the two and what you can do about UTI symptoms that persist after antibiotic treatment.

Bacterial Resistance

Here are some questions to consider:

  • How many pills did your physician prescribes for you?
  • Is this your first UTI?
  • Did you have any flank pain?
  • How long have you been experiencing your symptoms?
  • Can you try NSAIDs instead to relieve the symptoms while your body fights the infection?
  • Keep these questions in mind when discussing the length of antibiotic treatment with your physician.

A systematic review of 15 studies, including 1,644 women aged over 75 years, concluded that a short course of antibiotics (between 3 and 6 days, depending on the antibiotic) are as effective as long courses (7–14 days) for treating uncomplicated cystitis in older women.

The longer the duration of (unnecessary) treatment, the higher your chances of developing antibiotic-resistant bacteria.

However, do not shorten the prescribed course yourself and always consult with your prescribing physician.

Frequent Side Effects Of Cephalexin

Personally, when I took Cephalexin for my UTI, I tolerated it well. However, mild side-effects are possible.

Aside from yeast infections, the top three complaints we’ve seen related to Cephalexin are:

  • Allergies (most reported)
  • Thrush
  • Nausea

Other possible side effects include:

  • Diarrhea
  • Dizziness, feeling tired
  • A headache
  • Joint pain
  • Vaginal itching or discharge.

Other Antibiotic Options Besides Cephalexin For UTI:

Cephalexin And Pregnancy

There are no conclusive studies of using Cephalexin in pregnant women.

But from what we know so far, Cephalexin is very effective and complications to mother and baby are very rare.

Be Careful If Allergic To Penicillin

A study in the Journal of Investigational Allergology and Clinical Immunology found that if you have an allergy to penicillin, your chances of also having an allergy to cephalexin are almost 11%.

However, other researchers debunked this thinking by proposing that a history of penicillin allergy is a general risk factor for allergies to any antibiotics and is not specific to cephalosporins, such as Cephalexin. Also, it is possible that the risk of allergy to other antibiotics with a penicillin allergy is less than 10%.

12 Tips When Treating UTI With Antibiotics

  1. Take antibiotics 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 pills on time: Once you take your first pill, set your phone timer for 12 hours. Repeat it every time you take a pill until you are done.
  3. Plan ahead: Make sure to take your pills to work! For example, I separated mine into two containers so that I would always have some in my purse for the 3 p.m. dose while the rest would be near 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. If you stop taking the antibiotics early you’ll increase your chances of 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 an extra pill to make up for the missed dose.
  6. Stay sober: It’s better to avoid alcohol as it may worsen the side effects, and sometimes it can affect the effectiveness of a drug. Moreover, since 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 at the same time as the antibiotics your beneficial flora will recover to its normal state faster and you are less likely to develop a yeast infection. Wait a couple hours if possible to take your probiotic pill; do not take it at the same time as antibiotics, and snack on yogurt (without added sugars!) afterward.
  8. Revitalize your microbiome: Continue your probiotics after you finish the course of antibiotics. Make sure to buy special probiotics containing beneficial vaginal bacteria. This could help to prevent more UTIs in the future.
  9. Watch out for serious side effects: Do read the potential side effect of the antibiotics that your physician prescribed. Let your doctor know if you develop hives, diarrhea, vomiting or any other side effects. Know that some antibiotics (doxycycline, tetracycline, ciprofloxacin, levofloxacin, ofloxacin, trimethoprim) can make your skin more sensitive to the sun.
  10. Avoid Cipro: If your doc prescribed you Cipro, ask him/her if you can start with an alternative option. In 2016, FDA recommended against prescribing Cipro for uncomplicated UTIs, but there are still some physicians that are unaware of this. Let your doctor know this and be your own advocate.
  11. Take NAC supplements: If you are suffering from recurrent UTIs, learn about fighting bacterial biofilms. Some naturopathic doctors use N-acetyl Cysteine (NAC) supplements in hopes of destroying the “slime” bacteria produce to hide from antibiotics and your immune system. Ask your doctor about NAC supplements to potentially help destroy bacterial biofilms.
  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 sugar, but the good kind that doesn’t seem to worsen diabetes.

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

 UTI Guides

  1. 8 natural strategies to prevent recurrent UTI
  2. 7 Unexpected Facts About Vaginal Discharge And UTI
  3. SEX and UTI
  4. Can I Get a UTI From My Partner?


  1. Using antibiotics responsibly: right drug, right time, right dose, right duration.
  2. The role of bacterial biofilms in chronic infections
  3. Cephadroxil promotes vaginal colonization with Escherichia coli.
  4. Effect of prophylactic, low dose cephalexin on fecal and vaginal bacteria.
  5. Antibiotic duration for treating uncomplicated, symptomatic lower urinary tract infections in elderly women.
  6. Cross-reactivity and Tolerability of Cephalosporins in Patients With Cell-Mediated Allergy to Penicillins
  7. Ten percent of patients who are allergic to penicillin will have serious reactions if exposed to cephalosporins
  8. Treatments for symptomatic urinary tract infections during pregnancy
  9. Supplementation of standard antibiotic therapy with oral probiotics for bacterial vaginosis and aerobic vaginitis: a randomized, double blind placebo controlled trial.
  10. 10.FDA Drug Safety Communication: FDA advises restricting fluoroquinolone antibiotic use for certain uncomplicated infections

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