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Metronidazole and Upset Stomach: What Users Say

Brand names: Flagyl, Metro, Flagyl 375, Flagyl IV, Likmez Metro IV

Upset stomach: mentioned by 197 users (8.1%)

Based on user experiences from 2,431 Metronidazole 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 33.7%
headaches 21.1%
dizziness 13.9%
diarrhea 12.4%
bad taste 10.2%
tiredness 9.7%
metallic taste 8.8%
upset stomach 8.1%
loss of appetite 7.9%
vomiting 7.8%

Reviews for Metronidazole

Commonly mentioned side effects
  • Rir...
  • Taken for less than 1 month
  • February 15, 2020

For Dental Abscess "Ok, so I am allergic to penicillin, so I have no choice but to take this antibiotic, but I would happily take it anyway over a dental infection any day! It usually takes about 2-3 days to kick in for me, some people sooner and some longer, but it does work! As for the side effects, please don’t let these comments put you off as medication works differently for everybody! I do get a bit of an upset stomach and a weird taste in the mouth, but it’s nothing that’s unbearable or unmanageable. I am still able to go about my day, and if you are in true pain of a tooth infection, then I think you would take a bit of a dodgy stomach over that unbearable pain!"

10 / 10
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150 Report
  • Nel...
  • Taken for less than 1 month
  • October 18, 2020

Metronidazole for Bacterial Infection "I have been ill since the start of June this year. Finally received a diagnosis of BV last Thursday. Very concerned about taking this antibiotic after reading about so many bad experiences. Well, I am happy to report that after taking 4 tablets to date, the only side effects I have experienced are a bit of dizziness after taking the tablet and slight stomach cramps, which resolve after about an hour. Hope this feedback offers some reassurance to someone. Oops, almost forgot - I actually feel that I'm starting to get my life back - feel so much better."

9 / 10
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106 Report
  • gin...
  • Taken for less than 1 month
  • September 25, 2019

For Dental Abscess "I had a tooth abscess for 3 weeks. I was on other antibiotics, and it kept getting worse. I started taking this drug, and within 24 hours, the pain finally started to subside. Yes, there are some stomach issues with this medication, but nothing compared to the pain from the dental abscess. I am so glad to find something to get rid of the pain and infection!"

10 / 10
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98 Report

Frequently asked questions

  • Jul...
  • January 20, 2021

For Bacterial Vaginosis "I am on day 4 out of 7 taking this metronidazole antibiotic. I was prescribed 2 per day. I have awful fatigue and brain fogginess. I feel like I am in a dream, my stomach is so sick, and I have super painful stomach cramping that had me in tears today. Diarrhea as well. I’m very nauseous even if I take this with food. This medication is very hard to take. I want to give up on it. I’ve never experienced side effects like this."

1 / 10
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75 Report
  • Net...
  • Taken for less than 1 month
  • November 17, 2019

Metronidazole for Bacterial Infection "Nah-ah. Never again. Worst medication I have ever taken. On my second day of taking this tablet, I was feeling nauseous. My appetite was bad, and my stomach felt sick. Headaches, fatigue, easily irritated. I dreaded taking it when the time came. It made me absolutely miserable. My resting heart rate went up to 105 bpm. Even raising my voice ever so slightly made my heart pound harder. It was very stressful. Steer clear. I felt stupid taking this medicine for side effects that were much worse than the reason I needed them for."

1 / 10
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86 Report

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  • non...
  • August 27, 2016

Metronidazole for Diverticulitis "This drug caused uncontrollable diarrhea and stomach upset, and I had to stop taking it after just 2 days. This was given for mild diverticulitis, and I got better with a liquid diet for several days, then low-fiber soft food, and then graduated to regular foods. I had another bout of diverticulitis 4 months later and just did the diet - didn't go to doctors or use antibiotics. For my mild cases, this is the way to go. This drug caused more harm than good."

1 / 10
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78 Report
  • Sna...
  • October 2, 2018

Metronidazole for Bacterial Infection "I went into the hospital on Saturday with extreme stomach pain and constipation. CT scan and blood work showed colitis with a bacterial infection. Prescribed 500 mg Flagyl 3x a day and 500 mg Cipro 2x a day. I've taken Cipro before but had never heard of Flagyl. I made the mistake of reading reviews and became panicked. But most people don't leave reviews when things are good. I'm on day 3, but things are okay. I have to take it with milk. Keeps the nausea and metallic taste to a minimum. I have mild stomach upset (but nothing compared to before) and a headache. It's not pleasant, but I'm almost halfway through. My suggestion is to eat and drink different things. I also found spacing out the Flagyl and Cipro helped with nausea as well. The medicine seems to be working. And the side effects have been bearable so far. Take each review with a grain of salt and remember-every body is different and will respond to things differently."

10 / 10
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More FAQ

  • Inf...
  • Taken for less than 1 month
  • October 17, 2019

For Bacterial Vaginosis "The bad reviews and side effects scared me. I don't need more toilet/cry time. So I did this to have zero loose stools and barely lowered mood: -Set up your phone alarm so you don't miss a dose. -Dose at equal times apart. Your body will benefit from consistent levels of antibiotics (AB). If you dose early, you get more side effects. If you dose late, bacteria can grow back. Example: For two doses per day, dose 24 ÷ (2) = 12 hours apart. -Take probiotics (PB) between your AB. AB kill both good and bad bacteria. Without good bacteria, your mood worsens (look up 'mood gut'). PB restores a healthy gut. I took AB twice a day; this was my alarm clock schedule: 10 am-AB, 4 pm-PB, 10 pm-AB, 4 am-PB (I'd wake up, eat a bit, dose, then back to sleep.) -Take all your AB. Follow these tips to get fewer side effects. Take all your AB to save humanity from AB-resistant bacteria! -Eat some food before you take either AB or PB to avoid upset stomach from AB and to get more benefits from the PB."

8 / 10
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50 Report
  • She...
  • Taken for 1 to 6 months
  • September 5, 2020

For Diverticulitis "This is my second flare-up with diverticulitis since March of 2020. My own fault due to my bad choice in foods. This combination of Flagyl and Cipro makes my stomach ache, urine is dark and foul-smelling, my stomach pulses, headache is mild, joints hurt, nausea, dizzy the first 3 days. It is very stressful on your body. My diverticulitis is better, but the side effects of the treatments take a toll on your body. I find too, if I stick to taking a good probiotic with slippery elm and drink daily a full glass with a teaspoon of psyllium husk mixed in, I do not have any issues. But if I backside and slack off performing this daily regimen, then I flare up. Pizza, especially pepperoni, is a BIG NO-NO."

10 / 10
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38 Report
  • lov...
  • Taken for less than 1 month
  • June 22, 2020

Metronidazole for Bacterial Infection "I have SIBO, and my doctor prescribed Flagyl 250 mg 3 times/day for 14 days and Rifaximin 3 times/day for 14 days to treat SIBO (small intestinal bacterial overgrowth). Overall, my experience with Flagyl was unpleasant. I experienced moderate side effects that made me feel worse, so I stopped after 4 days and kept on the Rifaximin with no problems. On Flagyl, I experienced fatigue. When I tried to work out to boost energy, I felt horrendous: nauseous with flu-like symptoms. I experienced loss of appetite for normal healthy foods and found that I was binging on unhealthy foods. A slight metallic taste in my mouth, and a moderate feeling of upset stomach that came and went. Also, moderate bloating. If I had been extremely sick and Flagyl made me feel better, I may have kept on it, but for someone with mild SIBO, this drug wasn't worth it. If you're only mildly ill, I'd suggest finding an alternative medicine, if possible."

4 / 10
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39 Report
  • RaR...
  • Taken for less than 1 month
  • January 20, 2017

For Diverticulitis "I was diagnosed with a mild case of diverticulitis. I had severe abdominal pain, mainly on the left side, a low-grade fever, and a headache. I was prescribed Flagyl every 6 hours for 10 days and Bactrim every 12 hours for 10 days. Ugh... 60 pills..... I felt much better abdominal-wise after 2 days, but the side effects were horrible! Sour stomach and headaches... After day 4, I decided to do some research. I learned that you should space these meds at least an hour apart (helped a ton). You should also eat a piece of bread or have something on your stomach when you take them. Drink as much water as you can and take prebiotics and probiotics to help your stomach stay balanced. I was also recommended to take a Leaky Gut Repair health supplement."

10 / 10
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54 Report
  • sav...
  • Taken for less than 1 month
  • May 23, 2021

For Dental Abscess "Considering a dental abscess is probably the most pain I’ve ever been in, the metronidazole side effect of a slightly upset stomach I had was definitely a walk in the park. Took 500 mg 2x a day for 7 days, cleared up the infection immediately, and I felt better by dose 3. Usually, I ate something soft (banana, applesauce, eggs, or seasoned rice) before I would take it and had no nausea or throwing up. My stomach occasionally did “whale mating” sounds, but that’s not abnormal for me, lol."

10 / 10
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29 Report
  • Ano...
  • November 21, 2016

For Diverticulitis "Had pain in my lower left quadrant. Thought maybe had a partial blockage. On the third day, went to the ER, got blood work done, got an X-ray, found nothing, blood work came back with elevated white blood cell count. Doc orders a CT scan, turns out I have acute diverticulitis (I'm 30). The drugs (Cipro and Flagyl) work, pain subsided, and I can imagine they're fighting the infection as I write this, but man, the side effects are pretty terrible. Nausea, dizziness, upset stomach, metallic taste in mouth, and feeling crappy overall from the side effects. I'm on day 3, like most reviews on here, it seems like the make-or-break moment. The pills are progressively harder to ingest because I dread the side effects. BUT I gotta let the meds run their course."

8 / 10
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  • CBa...
  • July 16, 2019

For Diverticulitis "I have had diverticulitis for several years now and had my first partial bowel resection after I was extremely ill and diagnosed with a perforation. Since then, I have kept a combo of aerobic and anaerobic antibacterial meds on standby. I agree with a few other people... Cipro is extremely bad for you. Flagyl isn’t great either, but my Cipro experience was the absolute worst. I have never had side effects from any medications ever... until this one. My doctor changed my regimen and I am now on a Keflex + Flagyl combo. It works, but I still get a prolonged upset stomach for a number of days after finishing the 10-day cycle. I find taking chewable Gravol and eating yogurt, eggs, and drinking plenty of fluids does help. Diverticulitis completely sucks. And I’m sorry all of you who have posted are enduring this disease. Do what you can to avoid the resection. It is absolutely horrible."

7 / 10
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37 Report
  • Anonymous
  • May 26, 2020

Metronidazole for Diverticulitis "I am on the 5th day! The last day of metronidazole 500 mg twice a day! I don't recommend this antibiotic to anyone. I have had the most vivid, worst nightmares on this drug. My stomach cramps, and hurts, and I have diarrhea bad. I feel like my eyes are so dry and have a brain fog, and don't know if I'm coming or going. Side note, it cleared my diverticulitis up, though."

5 / 10
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31 Report
  • Nan...
  • Taken for less than 1 month
  • September 29, 2020

For Bacterial Vaginosis "I got prescribed 500 mg metronidazole twice a day for 7 days for BV. By day 4, I had extreme nausea, dizziness, irritability, and trouble falling asleep. On day 5, I woke up with awful stomach cramps, got out of bed to throw up, and ended up fainting. I felt mentally out of it the whole time I was on them. It cleared the infection, though. I don't really want to experience this again. Also, the taste is god-awful."

3 / 10
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30 Report
  • chu...
  • Taken for less than 1 month
  • October 19, 2019

For Diverticulitis "I was prescribed this metronidazole along with Cipro (for diverticulitis) and have to say it stopped my pain within a day. I suffered some stomach discomfort, but nothing severe, and had none of the bad side effects people have mentioned here."

9 / 10
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31 Report
  • Sea...
  • Taken for less than 1 month
  • March 26, 2015

Metronidazole for Diverticulitis "First off, don't forget that a lot of people are probably doing excellent with little to no problems with this antibiotic. Sort of like you never really hear from happy customers, usually the unsatisfied ones. Also, that everyone's body reacts differently. ...that being said, Holy Cow, the nausea! Ugh... Stomach cramps and pretty much constant nausea all day today (day 2). Eventually, had to leave work early. Pepto did not help. Going to try taking Nauzene with me to work tomorrow, see if it helps. (OTC nausea medication - a lifesaver in the past) Taking it with Cipro. Been on this combo before for my diverticulitis without so many stomach problems. Still a better option than the huge waves of pain from a flare-up."

8 / 10
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51 Report
  • Anonymous
  • Taken for less than 1 month
  • October 30, 2012

Metronidazole for Bacterial Infection "My doctor gave me this because I had bacterial vaginosis. Not even 12 hours into my first dose, I got the metallic taste in my mouth, then severe stomach cramps and nausea. I'm on day 5 and have had bouts of nausea throughout the course of my medication. My appetite has gone way, way down, and I'm so tired! I literally will sleep 12 hours and then get up for 2, then go back to bed for another 4! Having trouble staying awake at work, but it is doing its job!"

9 / 10
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52 Report
  • Eva...
  • July 28, 2009

Metronidazole for Bacterial Infection "I had a vaginal infection and was prescribed Flagyl to cure it. I hated the immediate awful taste in my mouth, and it dissolved immediately upon hitting my tongue. I only experienced the awful taste and some slight stomach upset as side effects. The infection began to clear up after 3 days of a 7-day prescription. I recommend it, and drink something fruity with it. Also, DO NOT DRINK ALCOHOL AT ALL while on this medication OR FOR 3 DAYS AFTER YOU STOP TAKING IT. You WILL have severe vomiting, heaving, and dizziness."

8 / 10
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65 Report
  • UN...
  • Taken for less than 1 month
  • November 9, 2019

Metronidazole for Bacterial Infection "Prescribed this medicine for an infection I got after getting an IUD inserted. 500 mg metronidazole twice a day. Took them at 8 am day one. No issues day two. Up at 4 am, had symptoms of bloating, stomach gurgling, cramps, explosive diarrhea, extremely liquid stool, pain. All subsided by 11 am next day. Day three. Up at 1 am. Bloating, stomach gurgling, doubled from the night before. I had cramps, diarrhea, but not as bad as the night before, and I swore that I was done with this medicine. Drank a probiotic yogurt, and it’s been a while, 20 minutes with no gurgling... nope, I was wrong. Here we go again..."

1 / 10
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27 Report
  • Wor...
  • Taken for less than 1 month
  • November 9, 2015

Metronidazole for Bacterial Infection "Everyone's body will react differently to meds, genetics. Just because I had a bad experience doesn't mean you will. Took with a full stomach of bland food, 16 oz water, and took a daily probiotic. My experience with this medication was horrible. I was unbearably anxious, had a rapid heartbeat, intense pelvic pressure, bad stomach cramping, nonstop nausea, vomiting, and explosive diarrhea. This was my second time with this medication, with the same bad reaction. I had to discontinue both times. It took 3 days to start feeling better, 5 to 7 until normal. I'll never take this medication again. I'm sure it's good for others, but not me. I had cancer, so I've taken a lot of medications. Never had to stop another medication from side effects before, but I was scared to the point of going to the ER. Never again."

1 / 10
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36 Report
  • adi...
  • December 29, 2011

Metronidazole for Bacterial Infection "I just finished a 10-day treatment of 500 mg every 12 hours. I am so glad it is over. I experienced stomach aches, a metallic taste in my mouth, which I am still experiencing, as well as tingling/numbness in my tongue. I am also experiencing itchy and a burning sensation in the vaginal area, it is uncomfortable. I hope it goes away soon. The only good thing about all this is that I don't have that fishy smell anymore."

7 / 10
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43 Report
  • Naa...
  • Taken for less than 1 month
  • March 12, 2019

Metronidazole for Bacterial Infection "I have taken Flagyl multiple times for BV. I hate it each time. I tried clindamycin, but it wasn’t as effective. I took the pills with chocolate milk for the first few days, then orange juice. Then I finally saw where to wrap a fruit roll-up around the pill. I wish I would’ve known about that a long time ago. It helped a lot. My side effects were: dizzy, drowsy, stomach ache, heartburn, kind of blurry vision, headaches, back pain, frequent urination, dark urine, not much diarrhea, nausea. Finally, I didn’t have a metallic taste, but the aftertaste was awful. After taking the medication, it did give me a yeast infection, which was expected. Really, please try the fruit roll-up method, it helped a lot even with my last tablet."

9 / 10
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24 Report
  • Anonymous
  • December 11, 2008

Metronidazole for Bacterial Infection "I took this in February of 2008, and in December 2008, I was diagnosed with the same bacterial infection again. The doctor said this is the best medicine available to kill the bacteria. The pills are horrible to take since they are not coated. I've experienced the metallic taste and stomach upset feelings. However, if they work, I am willing to withstand this temporary inconvenience."

9 / 10
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51 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.