How and When to Re-Challenge FODMAPs

So, you’ve successfully eliminated FODMAPs and had a few weeks of symptom improvement? Yay! Now, you’re ready to re-challenge FODMAPs but you don’t know where to start? You’re wondering when and how you’re supposed to go about this phase of the diet? Well, you’re in the right place.

The re-challenge phase is the second of the 3 phases of the Low FODMAP Diet (find out more about the diet here). It’s the phase that actually lets you work out what your unique triggers are, which is the whole point of the diet. If you’re not convinced about why it’s important that you do this phase, have a read of my last post (here). Once you’re clear on why it’s important, keep reading!

If you’ve had some success by eliminating FODMAPs and seen a reduction in symptoms, that’s great! Now it’s time to work out which specific FODMAPs were causing problems for your gut. By doing this, you’ll finally understand what foods don’t work for you. You’ll be able to develop a personalised Low FODMAP Diet, that does work for you!

Speaking from experience, this phase is quite difficult and tedious, as you have to test each FODMAP group individually. It takes a bit of time and you need to have a plan. I’m here to give you some pointers to help you plan it out properly. This will help you avoid some common mistakes and get some answers as soon as possible!



Like I said, if you’ve eliminated FODMAPs and your symptoms have improved, it’s tempting to just keep going. Or maybe you know you need to re-challenge FODMAPs but you’re not sure how long you should wait.

Monash, the university that developed the diet (find out more here), recommend starting to re-challenge FODMAPs once you’ve seen an improvement in symptoms after 2-6 weeks on the Low FODMAP Diet. This is based on several studies they’ve carried out. Obviously, this isn’t clear cut and there’s quite a difference between 2 and 6 weeks. The whole diet is about working out what works for you and is very individual, therefore it makes sense that this bit is too. The point of the elimination phase is to establish a kind of ‘base’ level of symptom improvement. So, I would recommend staying on it long enough to have got to a stable level of symptoms.

If your symptoms have improved for a few days, that’s not long enough. If they went from a 9 to a 3 (using a scale of 1-10 where 10 is the worst symptoms) but then back to a 6 and then down to a 1, they’re not stable enough yet. However, if they’ve gone from a 9 to a 3 and this has stayed constant for a few weeks, that’s long enough. Within that 2-6 week period, wait until you’re happy that you could identify what your new ‘base’ level of symptoms are on the Low FODMAP Diet, on a scale of 1-10. Once you can do that, you’re ready to move on.


Now you know that you’re ready to re-challenge FODMAPs, how exactly do you go about doing it? Which foods do you re-challenge, how much of them do you eat and when do you eat them? Although some initial studies have been carried out, with some strong evidence, there’s still limited data to determine exactly how this phase should be carried out. That’s why it’s important to remember that what I’ll advise here, and what other people will advise, is a suggested plan to follow. However, it isn’t a strict protocol and it’s ok not to follow it perfectly and to adapt it to suit you. As long as it helps you to figure out your triggers, it’s ok.

The ‘re-challenge approach’ really just gives you a system to help work out how you tolerate each FODMAP sub-group. The aim is to try foods from the different groups, see if you get a reaction, and then know whether you tolerate it or not. Each food you try is called a ‘challenge’ and you’ll do challenges one at a time so you can be sure it’s that food causing the reactions (if you get them).



  • Timing - You will need to complete each ‘challenge’ one at a time, over a 3 day period

  • Background Diet - Other than the food you are using to re-challenge, keep the rest of your diet low FODMAP throughout the re-challenge phase

  • Symptoms - During each challenge, you should record the type of symptoms (e.g. bloating/pain/wind) and the severity (e.g. mild/moderate/severe), if you have any. If your symptoms get really bad at any point, stop re-challenging that food. If you tolerate the food with no or mild symptoms, keep increasing the dose of it up to the normal serving size you’d have.

  • ‘Washout’ - A 2-3 day ‘washout’ is recommended between each new FODMAP sub-group that you challenge. This is a period where you go back to the Low FODMAP Diet, to give your gut a chance to reset



Each challenge takes 3 days or 5 days (with fructans & GOS, a day in between challenge days is advised). They should be followed by a 2-3 day washout period. Therefore, I’d recommend putting aside a week to challenge each FODMAP sub-group. This allows for fructans/GOS and, for other sub-groups, an extra day if anything doesn’t go quite right, you have a big event on one day, or you need an extra day of washout to get your gut back to ‘normal.’

There are 8 FODMAP sub-groups that Monash recommends to re-challenge, so this phase usually takes 8 weeks. However, it’s very individual and can be done more quickly if you take less than a week for each challenge. It can also take longer if there are any complications, e.g. holidays, that cause delays, or you want to challenge any other foods.



The table below gives you my suggestions on which foods to re-challenge for each sub-group, the amount to try and when you should try it.

The foods here are recommend because they only contain one FODMAP sub-group. E.g. milk is high in lactose but doesn’t contain any other FODMAPs. If you test using foods that contain multiple FODMAP sub-groups, you won’t know which one it is that’s causing the reaction, if you get one.

FODMAP Re-challenge foods and portion sizes

This table is just a suggestion. There are lots of other foods you can use as test foods, and there is a lot more detail to this phase. If you want to invest in a book that covers only this phase, I’d highly recommend Lee Martin’s book (get it here). This is one of the resources I used when I was planning how to re-challenge FODMAPs.

The other thing to mention is that you can adapt the order, the foods, the amounts, etc, to you. You can really individualise the phase to make it fit in with your lifestyle and your preferences. For example, I personally tested onion and garlic separately as I suspected I’d be highly sensitive to them. I also changed the amount of milk I tested, as I would never normally drink 375ml of milk. On top of that, I had some big events planned during the re-challenge phase, so I built in some breaks.

Next week, I’ll be dedicating a post to how to really individualise the phase and re-challenge FODMAPs in a way that fits in with your life. If you sign up to my newsletter below, it’ll be sent straight to your inbox.


  • When: it’s time to re-challenge FODMAPs when you’ve:

    1. Been on the Low FODMAP Diet for 2-6 weeks

    2. Seen an improvement in symptoms

    3. Established a new ‘base’ level of symptoms on a scale of 1-10

  • How: there is no set way to re-challenge FODMAPs, but it will make the process easier if you follow a guide!

  • How long: it normally takes about 8 weeks to completely re-challenge FODMAPs

  • Foods & Portion Sizes: see the table above for some guidance

  • Tailoring the phase to you: it’s 100% possible to tailor the phase to your lifestyle and your food preferences, so it fits in with your life. I’ll be covering how to do that next week.

Thanks so much for taking the time to read this. Has this helped? Let me know in the comments!

Sophie x

Sophie BibbsComment