If you’re starting a course of probiotics, it helps to have realistic expectations about how quickly they will start working. You don’t want to give up on your probiotic supplements before they’ve had a chance to improve your well-being. You also don’t want to waste money taking probiotic products that don’t have any health benefits for you.
Based on my observation in the clinic, some patients notice the benefits of probiotics as soon as 1-3 days. For others, it takes as long as 2-3 weeks to see the effects of probiotic supplementation. A look through the research generally supports my observations about how quickly probiotics work, with one interesting exception. Here’s a summary of the research results:
Research Summary: How Soon Do Probiotics Start Working?
Dairy Intolerance (and possibly other food intolerances) 
0.5 – 3 years
There are hundreds of studies that show the benefits of probiotics for a wide variety of medical conditions including digestive problems (like IBS, bloating and even Crohn’s disease) and non-digestive symptoms. However, most studies don’t collect daily symptom data. That means that, for most studies, we know that probiotic supplementation was effective but we don’t know how quickly it worked.
Despite the lack of data on this topic, we can infer that in most cases, you can expect your probiotics to start working in 1-4 weeks, similar to the results that have been shown for irritable bowel syndrome (IBS). That’s because, for IBS and many other medical conditions, probiotics work by restoring balance in your gut bacteria, addressing the root cause of symptoms.
Exception #1: Probiotics May Treat Acute Diarrhea in 1-3 Days
Research shows that probiotics work in 1-3 days for acute diarrhea. , , 
This is great news if you come down with a case of traveler’s diarrhea!
And of course, as with any supplements, there are some who experience great results sooner due to what is referred to as the Placebo effect. In other words, by expecting and believing that the probiotic will work, they experience beneficial effects. Our thoughts are powerful.
Exception #2: Probiotics May Improve Food Intolerances Gradually
Preliminary research shows that probiotics can be helpful for reducing dairy intolerance.  However it takes between 6 months and 3 years.
This study corresponds with what I have seen in my clinical practice. As patients improve their gut health, bloating, fatigue, mood, and many other symptoms can start to abate fairly quickly. However, food intolerances do persist much longer. The good news, as I have seen many times, is that as gut health improves, food intolerances often do diminish over time.
In addition to taking probiotics, it can be very helpful to identify and eliminate foods that trigger symptoms. There are a few diets, like the Paleo diet and the low FODMAPs diet, that are designed to help you identify food intolerances and are excellent tools for improving your gut health.
And while it’s important to avoid foods that trigger reactions, I encourage you to gradually reintroduce foods and broaden your diet as much as possible over time. It can take some trial and error and it isn’t always a linear process. You may test a food item several times and continue to react and then suddenly you find you are able to tolerate it in moderate quantities.
Based on the research so far, long-term probiotic supplementation is likely to support this process.
Bottom Line: For most conditions, take probiotics for at least 3-4 weeks to see if they work for you. Acute diarrhea and food intolerances are exceptions to these guidelines.
How Probiotics Work
Probiotics don’t work like most drugs that directly target your symptoms directly.
Instead, probiotics work by balancing your gut flora and reducing the burden of pathogenic microorganisms. As the bacteria in your intestinal tract becomes more balanced, the immune system calms and inflammation reduces. As your gut bacteria become more balanced and your digestive health improves, your overall well-being (energy, mood, cognition, hormonal balance) also improves.
This process explains why it takes time for probiotics to work. It also explains why probiotics have so many different health benefits and few side effects. Research shows the benefits of probiotics for a wide variety of medical conditions, including IBS, Crohn’s disease and colitis, gut infections, mood, sleep, thyroid health and more.
For a science-based list of medical conditions that benefit from probiotic supplementation, see my Probiotic Starter Guide.
How to Know if a Probiotic Works for You
Probiotics work well for many medical conditions. But they’re not a panacea that’s guaranteed to work for everyone.
I recommend a 3-4 week trial of probiotics to test their effectiveness for you, even if you’ve tried probiotics before. But it’s important that you do a full and complete trial and follow a few guidelines.
Get It Right in One Go
A lot of people try probiotic supplements without really knowing which probiotic strains to buy or how long to take supplements. They may go on and off probiotic products, trying different brands or different strains of probiotics, hoping for better results. They also may not be informed about selecting a high-quality probiotic supplement.
I call this the probiotics merry-go-round and it can be a waste of time, energy and money.
Here is some simple advice for implementing an effective probiotic trial. It takes less than a month and will keep you off the probiotics merry-go-round.
Select a High-Quality Probiotic Supplement
The Food and Drug Administration (FDA) doesn’t actually review the quality of probiotics and research shows that some probiotic supplements are not worth buying.
The two most common reasons probiotic products don’t work are:
Not meeting label claims
Containing potentially harmful organisms
Here’s what the research shows:
Of 26 commercial probiotics assessed in this study, none fully supported label claims, and some of them contained unacceptable microorganisms .
One study found only half of the probiotics examined had the specific probiotic strain listed on the label .
Another study found 43% of the probiotics assessed contained less than half the amount of healthy bacteria listed on their labels .
You don’t need to purchase the most expensive probiotic supplements. But, you should be wary of a probiotic product that is substantially cheaper than the rest. This usually indicates corners have been cut in the quality assurance measures.
For specific information on what you should look for in a high-quality probiotic supplement, see my Probiotic Starter Guide.
Selecting the Right Probiotic Strains
There are a lot of different probiotic strains, but all you really need to know are the three main probiotic categories. Nearly every probiotic product can be classified into one of these categories .
These are the most well-researched, with over 500 trials assessing their validity. These live beneficial bacteria are also known as lactic-acid producing probiotic bacteria. They typically do not colonize the host but do improve the health of the host.
The second most researched probiotic, with over 100 studies. Saccharomyces boulardii (S. Boulardi for short) is not a normal part of the human microbiota, meaning it does not colonize us but does improve the health and well-being of the host.
The third most researched category of probiotics is soil-based probiotics. This group has roughly 14 clinical trials evaluating their effectiveness. This category is also known as spore-forming bacteria. This category of probiotic can colonize the host .
This is great news. This means you don’t need to try every probiotic strain on the market, simply pick one high-quality probiotic product from each category.
You also don’t need to match specific probiotic strains to specific medical conditions. All strains of probiotics work in a similar way by addressing the health of your digestive system. One category of probiotics may be more effective for you than another, simply because of the unique profile of gut flora in your intestinal tract.
You can also add healthy, probiotic-rich foods like kimchee, tempeh and Lacto-fermented sauerkraut to your diet. Just don’t expect these to take the place of supplements as the amount of probiotics they contain are much lower.
Ensure Your Probiotic Trial Works – Take All Three Categories of ProbioticsTogether
The 3 for BALANCE Probiotic Protocol was developed to give you full exposure to all 3 categories of probiotic bacteria. This approach can be very effective for those who have had poor results with a more haphazard approach to choosing probiotic strains.
Start by taking all three probiotic strains, together, for a trial period of 3-4 weeks.
How to Monitor the Effectiveness of Your Probiotic Supplements
When improvements to your well-being are gradual they are sometimes easy to overlook. Keeping a written record of symptoms can be very helpful.
Here’s an approach that will help you to be as objective as possible in monitoring the effects of probiotics during your trial:
1st – Take stock of your symptoms
They might be fatigue and depression, or bloating, or joint pain, or constipation, or insomnia, or an unstable dose of thyroid medication. Whatever they are, take stock of how often and how severe your symptoms are.
2nd – Reevaluate symptoms after 3-4 week on the probiotic protocol
Are you improving? If so, keep on the probiotic protocol. You are not looking for a complete resolution. If so, that is great. But don’t expect everything to be fixed completely at the 3-4 week mark. You are looking for a clear trend of improvement. If so, great, we are on the right track. Keep going.
3rd – Look for when you hit your peak improvement
Once you peak or plateau, great. This is another milestone. Keep this constant for another four weeks, so your body can integrate and you can lock in this new level of good health.
After four weeks…
Finally – Try to gradually find the minimal effective dose
Technically, you don’t have to do this but I find less is more with supplements. I like people to cut their dose of probiotic supplements in half, then reevaluate after 3-4 weeks. If this goes well try coming off your probiotics completely.
There is no one right way of weaning off your probiotic dose. You may want to try a different method. If at some point your symptoms return, it means you should stay on the probiotics. You can try weaning again in a few months.
Probiotics can safely be used in the long term, so if you consistently notice you feel better on them that is OK.
If Symptoms Return
You can be going along great and then something derails your gut health. Things like travel, stress or a significant period of poor self-care might lead to a regression. It’s OK, life happens. Don’t be hard on yourself. Simply return to the full 3 for BALANCE probiotic protocol, and then later you can again wean your dose.
What to Do if Probiotics Aren’t Working
If you have been taking a high-quality probiotic supplement and following the 3 For BALANCE Probiotic Protocol for 3-4 weeks, and you don’t experience any change in symptoms, you can be confident that you don’t need to try another probiotic product.
With probiotics, you have laid an important foundation that can make other, subsequent, gut therapies more effective. For example, some people have stubborn imbalances in their intestinal bacteria that may require more than probiotics. Antibacterial treatments like herbs or even select antibiotics can help here. Studies have found that probiotics make antibacterial treatments more effective. So we start with probiotics and then consider additional support if needed.
I care about answering your questions and sharing my knowledge with you. Leave a comment or connect with me on social media asking any health question you may have and I just might incorporate it into our next listener questions podcast episode just for you!
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