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Keflex and Upset Stomach: What Users Say

Upset stomach: mentioned by 7 users (7.7%)

Based on user experiences from 91 Keflex reviews, the following table shows the most commonly mentioned side effects.

All user comments are moderated by Drugs.com. Each review is verified for relevance and screened for inappropriate content. Side effects are user-reported and not clinically verified.

nausea 14.3%
diarrhea 9.9%
headaches 8.8%
upset stomach 7.7%
dizziness 6.6%
tiredness 5.5%
depression 4.4%
fatigue 4.4%
gas 4.4%
itching 4.4%

Reviews for Keflex

Commonly mentioned side effects
  • Jea...
  • Taken for less than 1 month
  • May 28, 2019

For Bladder Infection "Took a 500 mg dose of Keflex twice a day for one week - I had a UTI. Side effects were diarrhea, headaches, felt depressed, upset stomach, and nausea. Now I’m having stomach cramping. Just hope the urinary tract infection I had is gone after taking this strong antibiotic."

10 / 10
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  • Jea...
  • Taken for less than 1 month
  • May 28, 2019

For Bladder Infection "Took a 500 mg dose of Keflex twice a day for one week - I had a UTI. Side effects were diarrhea, headaches, felt depressed, upset stomach, and nausea. Now I’m having stomach cramping. Just hope the urinary tract infection I had is gone after taking this strong antibiotic."

10 / 10
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52 Report
  • Anonymous
  • July 22, 2011

For Skin or Soft Tissue Infection "Works very well for treating the cellulitis I got from an insect bite. But don't drink alcohol while you are on this medication. I had half a beer and started feeling really nauseous, had a migraine and my stomach hurt."

10 / 10
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87 Report

Frequently asked questions

  • Ama...
  • Taken for less than 1 month
  • September 14, 2018

For Bladder Infection "I have constant battles with UTIs, so I’ve taken a lot of different antibiotics. Keflex is definitely a good one, but for me, I have to take 500 mg three times a day, so I get some side effects, mostly tired, stomach cramps, and dizzy. It’s not bad, though, like some of the other ones I’ve taken. Before I had repeat infections, I had the 500 mg twice a day dose and had very minor cramping from that dose. It’s my go-to when I can take it. Drink lots of water with it too, it helps flush your system faster and get rid of the infection and its side effects quicker."

9 / 10
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47 Report
  • Ros...
  • Taken for less than 1 month
  • August 7, 2020

For Bladder Infection "I had cystitis and was put on Macrobid for 5 days, only to find out it didn’t do a thing for the infection. My Dr. gave me an injection of Rocephin in the office and suggested Keflex for 7 days, three times a day (500 mg). The Rocephin gave me a stomach ache and diarrhea, then I took Keflex, and it made me queasy the rest of the day. The second pill I was fine and have remained side effect-free since then. I finish my course tomorrow but still feel the cramping and mild pain from a UTI, so I’m not sure this antibiotic worked either. We’ll see!"

9 / 10
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7 Report

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  • Anonymous
  • November 12, 2020

For Bacterial Infection "I had an infection on my nose. I was happy how Keflex cleared up, but the side effects were terrible... stomach cramps, gas. I was down for 3 days."

7 / 10
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8 Report
  • Sta...
  • Taken for less than 1 month
  • September 24, 2021

For Skin or Soft Tissue Infection "Very bad reaction to this medication. Multiple bouts of diarrhea and stomach cramps."

1 / 10
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5 Report

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Reviews may be edited to correct grammar/spelling or remove inappropriate content. Reviews appearing to come from parties with a vested interest are not published. This information is not intended to endorse any medication and should not replace the expertise and judgment of healthcare professionals.