How Long Do Probiotics Take to Work?

Written by: Kari Raman, PharmD, RPh
Published April 13, 2023

Many people who come into the pharmacy who are taking probiotics want to know how long it is going to take for the probiotic to work. There is no easy answer to this question but generally it will take a few days to a few weeks to see the effects of probiotics. The difference will depend on the aliment you are trying to correct, the dose, the purity, your body’s normal flora, and your body’s response to the probiotic.


Side effects you might notice right away


In the first few days of taking a probiotic, people may experience bloating and diarrhea while the body is getting used to the change in microbiota. These side effects should subside in a few days after your body has adjusted the new balance in your system. To get the most benefit from probiotics, you should take the supplement at night, so that the good bacteria have enough time to improve digestive problems without interference.


How long probiotics take to work

Generally, if you are using probiotics to correct diarrhea it should start working in a few days. As stated in research by NIH, the 2-day treatment of diarrhea was more effective in the probiotic group than the control group.  The overall effects of probiotics like digestive issues or immune improvement are seen in the body when the bad bacteria and the good bacteria are in balance and inflammation has decreased. With this said, probiotics for these ailments will generally take two to three weeks to fully work. Research suggests that it can take up to 8 weeks for probiotics to start to work to reduce the symptoms of IBS.


To summarize, probiotics have shown to improve acute diarrhea in about two to three days, where more intensive bodily issues like immune health and improved digestive problems will take 2 to 3 weeks to see improvement. One related question I answered is how long probiotics stay in your system – it’s not that long if you stop taking them.


One common reason patients at my pharmacy want to take probiotics is because they are going to take a course of antibiotics. I’ve got a whole article on antibiotics – the summary is that the right strains can help prevent antibiotic induced diarrhea, in some people.

The table below summarizes what some medical research suggests is the time to show an impact.

Time to work for various conditions

Here is how log the research suggests it will take for probiotics to work for a few different conditions.



These different conditions are some of the signs that you need probiotics. Other conditions are frequent bloating and gas. And your doctor may suggest probiotics if you are trying to reduce inflamation or improve your immune system – but again, if you are worried about those conditions, talk to a doctor.

What Are Probiotics?

Probiotics are live microorganisms, often referred to as “good bacteria,” that can offer potential health benefits when consumed in adequate amounts – although there are also yeasts that are taken as supplements. These bacteria and yeasts are typically found in fermented foods like yogurt, pickles, sauerkraut, and kimchi or as dietary supplements. For some people, probiotics might play a really helpful role in maintaining a balanced intestinal flora by promoting the growth of beneficial bacteria and inhibiting the growth of harmful ones.

Potential Health Benefits of Probiotics

Probiotics may aid in improving gut health, and there’s growing research suggesting that they could have beneficial effects on various aspects of our well-being. They might assist in enhancing digestive function, reducing inflammation, boosting the immune system, and possibly alleviating symptoms of conditions such as irritable bowel syndrome (IBS) and diarrhea. There are a lot of studies, but many are small, so it’s not entirely proven that any specific strain or species is going to help any person with a particular condition. (I broke down some recent meta studies on IBS and probiotics, and there is starting to be some research that is pretty promising. That being said, it’s not a slam dunk for everyone and every condition.) So I always recommend that you talk to your doctor if you are having any health issues that you want to improve or before you begin taking a supplement – especially one that you’ll have to take for a number of weeks before the benefit starts to kick in. 

How Probiotics Work

When thinking about how long it takes for probiotics to work, it’s essential to understand their mode of action. Probiotics may contribute to restoring balance within the gut microbiota, leading to improved digestive health. They might alter the composition of the gut flora and modulate immune responses. The efficacy and the time it takes for probiotics to yield noticeable results may vary depending on individual health conditions, the type and strain of probiotic used, and dietary and lifestyle factors. However, as I’ve already written in this piece, it can take at least a couple of weeks before any benefits start to kick in. And that’s why some supplement makers, like GoodBelly, which I’ve reviewed, have 12 day challenges so people can give it enough time to start to work. 

Factors Influencing How Long Probiotics Take to Work

The amount of time it takes for individuals to experience the potential benefits of probiotics may vary due to differences in:

  • Body Composition: Each individual has a unique set of microbiota; thus, the effect of probiotics could be different for everyone.
  • Type and Strain of Probiotic: Specific strains might be more effective for certain conditions.
  • Dosage and Consistency: Regular and adequate intake is crucial for experiencing potential benefits.
  • Diet and Lifestyle: A balanced diet and a healthy lifestyle may enhance the effectiveness of probiotics.
  • Other medicines: Antibiotics and other medicines can have legitimate impacts on your gut.

Probiotics are live beneficial bacteria that might assist in maintaining gut health and could offer a variety of potential health benefits, such as improved digestion and enhanced immune function. The time it takes for probiotics to work can depend on multiple factors including the individual’s body composition, the specific probiotic strain, and overall lifestyle and dietary habits. Generally, effects like alleviation of diarrhea may be observed in a few days, while improvements in conditions like IBS might take up to 8 weeks or more. Consultation with a healthcare provider or a pharmacist can help in determining the right probiotic supplement based on individual health needs and conditions.


Pharmacist Kari Raman

I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

Probiotics are confusing!

One of the most common questions I get asked by patients is about probiotics. And the truth is, probiotics are not as well understood by the healthcare community as they should be.

So I’ve been reading a lot of probiotic clinical trials, and sharing what I’m learning here.

I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!