How long does it take for Metronidazole to work?

This article documents how long it took between taking my first Metronidazole tablet, to the pain actually beginning to subside. 

So, after struggling for 5 days with brutal tooth pain in one of my lower teeth, I finally bit the bullet (excuse the pun) and decided to take a trip to the dentist. I booked my appointment, arrived promptly and was called into my dentist’s brightly lit office. I was asked to take a seat in the dreaded dental chair, pop on my safety specs and was then gently reclined backwards. That weird oblong light was focused on my teeth while she took a good look at the offending tooth.

She asked me a few questions and then tapped it this way and then tapped it that way whilst asking “does this hurt?” and “does that hurt?”. After giving her my answers she said “good, it looks like the nerve is still alive”. As reassuring as this was, it was still horribly painful, especially after being clouted a few times with her metal implement.

She shoved a big plastic-like thing in my mouth and then pointed her x-ray gun at the throbbing tooth, whilst saying “I’ll get this over with as quickly as I can”. She scurried from the room to click the x-ray machine button. Trying desperately not to gag, I waited for her to remove the mouthful of plastic she had inserted whilst trying not to think of Steve Martin’s performance in the film “Little Shop of Horrors” (if you’re afraid of dentists, don’t watch the film!)

She looked at the x-ray photo on her computer screen and told me I had a “pocket” some 5mm to 7mm long below the gum line that had become infected with bacteria. Within seconds, she’d written me a prescription for the antibiotic, Metronidazole.

Medicines, pills and tablets

Now, I haven’t taken any antibiotics for many, many years and try to avoid them if I can. However, as the pain was so bad, other than getting her to yank the tooth out there and then, it seemed like there were few other options available to me, aside from a root canal; and I didn’t want one of those. During my five day ordeal, I’d tried various things like salt water mouthwashes and even rubbed raw garlic on my gum (which actually worked quite well as a temporary pain relief, although it burned like hell at first).

My Metronidazole dosage

She prescribed me a 5-day course of Metronidazole. One tablet was to be taken 3 times a day and each tablet was 200mg. She reassured me that this would kill the infection and warned against drinking alcohol during the course as it would make me “very sick”.

Always read the label!

Now, I’m not really one for reading labels or the folded up paper that is always in medicines boxes, but on this occasion, I thought it prudent to do so. Driven on by the non-stop, incessant pain, I’d do anything to maximise the chance of the antibiotic working to its full potential. After reading about all the scary potential side effects and noting that I also shouldn’t consume alcohol for 48hrs AFTER the course had finished, I took my first 200mg dose of Metronidazole.

When would the pain eventually subside?

It then dawned on me that I didn’t really know how long if at all, the Metronidazole would actually take to bring about some relief from the pain I was suffering. I’d already been taking regular doses of Ibuprofen and Paracetamol to ease the pain, but these were only effective for around an hour or so after taking them, and I was trying desperately not to exceed the stated dose.

This all happened during the week leading up to Easter so I knew that if it didn’t work, I’d be in agony over the long weekend. I already knew that antibiotics were reported to become less effective on the whole due to so-called “superbugs” developing a resistance to them through the general population’s systematic over-use of them. This had me worried; what if I was infected with superbugs that could laugh in the face of my Metronidazole, whilst merrily reproducing in my mouth?

After daydreaming about one end of a bit of string tied to my tooth, with the other attached to a door handle (as a last resort of course), I tried to remain optimistic. I decided to look on the internet to find out how long I might have to wait for the Metronidazole to take effect. It was more difficult than I thought to find a definitive answer but the general consensus seemed to be anywhere from 12 hours to several days!

When did my pain relief actually start?

After 12 hours, nothing but a slight increase in pain. After 24 hours, nothing but another increase in pain. If it wakes you up at night or you can’t even get to sleep, even with painkillers, the relentless pain begins to drive you insane. Thinking more about door handles, I just hoped the Metronidazole would eventually begin to work.

During this whole episode, there were virtually no visible signs of an infection aside from a slight reddening of my gum. However, after 36 hours and a feeling of swelling on my gum (when your tongue pokes around and you can detect it), I got out of bed and looked in the mirror. There it was, finally visible! The gum was swollen with a big red blotch on it; the antibiotics were finally starting to do their thing – thank goodness!


So there you have it, for me, it was around 36 hours before it began to ease the pain. I’m sure that for some of you reading this, it may be shorter (lucky you!) or it could even be longer; up to 3 days from what I’ve read elsewhere. My experience was one and a half days, almost to the hour.

If you’ve stumbled upon this post looking for the same information that I was, I hope you’ve drawn some comfort from it and your pain subsides quickly.

Disclaimer – This post is based on my own personal experience and should NOT be considered medical advice.

23 thoughts on “How long does it take for Metronidazole to work?”

  1. Thank you so much for sharing your experience. It’s always nice to get some reassurance when you have pain coupled with anxiety. A life saver

  2. I have overian cancer after being prescribed metronidazole 400mg 3 times a day for 5 days for a gum infection by day 2 causing headaches,so I have been reading up on the drug I am concerned as I read could be carcinogenic

  3. I have had tooth pain for about two weeks went to the dentist and said I need either root canel or my tooth out but couldn’t do it there and then had to book me in for Nov . But now I have covid . And my tooth pain is excruciating can’t sleep or eat so on top of covid It’s a nightmare .
    The dentist has given me amoxicillin and metronidozle and Diclofenac Pain killers . Nothing is touching the pain.. never felt pain like it . Can’t cope much longer I’m beside myself . I

  4. I’m 32 hours in I really hope in 4 hours the pain eases. I live with chronic pain and stomach condition means I can’t take ibuprofen. I’m struggling to cope with this pain. It’s got me at my limits. The thought of another night of no sleep fills me with dread but I have some hope now. Thank you.
    Covids fault, broke a filling in my front tooth but couldn’t have it fixed, so now have an access in the root of the tooth. Had two options have it out or save it. So next Wed have the nerve taken out root filled with antibiotic paste and temporary filling. Hope it works. But if not it’ll have to come out. So I’ll give covid one thing at least no one will see I’ve a tooth missing wearing a mask. Been good at hiding the hole left from the filling too.
    Thank you for this information, like you said couldn’t find it anywhere else. I know now only a few more hours to enjaw this pain.

  5. toothache is the worst especially when its a nerve pain with the dull ache, before the lockdown i was meant to of had my pre assessment at the hosital back in march for a full dental clearance because all my teeth basically got really weak and ended up broken to the gum line , im in agony with just one tooth which is the wisdom tooth it broke last year so i have half a wisdom top left and oh my god im in the worst pain ever, a month ago when it started couldn’t even lay down and even tilting my head was made the pain worse and my cheek and temple felt so sore even when just stroking my face is was sore i had this pain constantly for 16 days and it was awful to the point i was pulling my hair out because all i wanted to do was go to sleep i was so tired, i rang the dentist multiple times about this and because there was no obvious swelling they wouldn’t give me anything such as antibiotics but what they didn’t know is that i had some left over from a previous tooth infection which was Metronidazole and i took what i had left which was half the packet and day 3 this pain suddenly just started to ease and i was so grateful that i had them in the cupboard they were still in date which was a god send but today after 2 weeks the pain is back again my gum is red raw and puffy where the wisdom tooth is and im so worried that im going to have another 16 days of agonizing pain and no sleep. i just want this Covid 19 pandemic to sod off so i get back to the hospital and have it all booked to have them all out 🙁

  6. Update … it didn’t clear the infection (took away the pain though) so back on antibiotics this time amoxicillin and I’m waiting for an extraction and a root canal.

  7. Update … it took over 3 days for the pain to go. I’m on my 4th day and still a little bit of discomfort but bearable. I have spent much of the time in bed as felt so ill with it and had no energy. I used paracetomol, bonjela, clove oil and frozen veg to help with the pain. My tablets were 400mg. My only advice for the future, is to seek dental advice at the very first signs of pain however mild.

    • Hi Alison. Thanks for taking the time to post an update and sorry to hear it took so long. I agree that seeking dental advice immediately is definitely the best thing to do. The pain can come on pretty quickly if things are left without treatment.

      • too much descriptive novel type writing, i found myself having to skip as much as possible just to get to anything relating to “how long does it take to work”

  8. I lost half a tooth three weeks ago. Had it fulled. A week later agony. Dentist decided to extract it. Number up and started extraction – the worst pain I have experienced in my life.

    Sent home with a course of amoxicillin which I finished on the Friday. Pain began again over the weekend. Back on the Monday for second attempt at extraction. Got further but pain returned – sent home with a 5 day course of metradizanole. 1 day left and can still feel sensitivity in tooth. Terrified the extraction won’t work again.

    Anyone had this before? If the infection is resistant to both antibiotics what would be the next step?

    • My dentist told me that if the infection didn’t go, then deep cleaning was a possibility and if that didn’t work, extraction would probably be next. As it turned out in my case (which isn’t mentioned in the post), the metronidazole didn’t work and I had to go back to my dentist again.

      She gave my tooth a really deep clean which stripped away some of my gum around the offending tooth and showed me how to keep it clean.

      So far, I still have the tooth and the pain has gone. As a result, I’m slightly annoyed as it seems I didn’t even need a course of Metronidazole antibiotics in the first place if it had been properly cleaned on my initial visit.

      Please do let us know how things work out for you.

  9. Thanks for the post! I’m on countdown to 36 hours – hopefully. Been 27 hours so far. I’ve never known pain like it. I’ve also been sick a few times but unsure if it’s the co codomal causing the sickness so changed to paracetamol which numbs for pain for less than an hour.

  10. Thanks very much for your info, you have given me hope!! ? After visiting my dentist yesterday I am on the 400g tablets I’ve taken 3 in 20 hours pain worse and seems to be travelling further paracetamol dulls it for a while but not long, hope it kicks in soon ☹

    • Thanks for the comment Alison and I’m glad you found the post useful. At the time, I was amazed at how much pain something so small could produce!

  11. Thank you. You are correct, I can’t find this info anywhere! I just took my first dose and I hope it works faster than 36 hours. This isn’t fun.


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