Probiotics are live microorganisms that may benefit a person’s health. For short-term relief, some probiotics may work in a few days. For chronic conditions, it may take probiotics up to a few months.

Taking probiotics may help build and restore healthy bacteria in the intestines and promote digestive health. Probiotics may quickly treat some minor issues. For example, a person with minor diarrhea may see symptoms go away in a few days. For overall digestive health, it can take a few weeks of regular use before a person notices the effects.

Continuing to use probiotics over time may be most advantageous, as it takes time for these healthy bacteria to build up and benefit the body.

In this article, we explore what probiotics are, how to use them, and how quickly they work.

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Probiotics are living bacteria and yeasts that people may describe as ‘good’ or ‘friendly.’ Manufacturers of products containing probiotics may refer to them as ‘live cultures.’

Most probiotics contain microbes that thrive within the body in areas such as the small intestines and colon. Taking these probiotics may help support a healthy gut, as they allow the microbes to establish themselves in the body.

These microbes are not harmful and instead play helpful roles in the body, such as aiding digestion.

A digestive system that lacks these helpful bacteria, or has an overgrowth of harmful bacteria, is in a state of imbalance called dysbiosis. This can lead to digestive system symptoms and increase the risk for other issues.

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How quickly probiotics work will depend on several factors. A 2018 study found that the type of probiotic strain, health condition, product formula, product quality, and dose are all important for effectiveness.

Some may recommend probiotics for targeted therapy to treat acute symptoms, such as traveler’s diarrhea. In these cases, a person may notice the effects as soon as a few days later.

For example, older research suggests that in combination with rehydration therapy, probiotic treatment can help reduce the duration and frequency of diarrhea by 2 days.

For more chronic conditions, dysbiosis, or general immune health, it can take weeks of continuous use to see probiotics’ effects, while extended use may be better.

For example, a review in Nutrients notes that people with irritable bowel syndrome (IBS) may notice the most benefit when taking probiotics for 8 weeks or more. A 2018 study also shows that people who consume a high-dose probiotic drink for 12 weeks had significantly fewer upper respiratory infections than a placebo group.

Continuous use of the correct probiotics may offer the best chance for symptom reduction and overall gut health.

Probiotics contain a variety of microorganisms. The two most common types belong to groups called Lactobacillus and Bifidobacterium.


Commons strains of Lactobacillus include:

  • Lactobacillus (L) salivarius
  • L. acidophilus
  • L. paracasei
  • L. fermentium
  • L. brevis
  • L. casei
  • L. Sakei


Some common strains of Bifidobacterium include:

  • Bifidobacterium (B) bifidum
  • B. longum
  • B. breve
  • B. animalis

Probiotics are usually added to certain foods or are available as supplements.

Eating probiotic foods

Some foods may naturally contain probiotics, while some companies may add them to products during the manufacturing process. Fermented and dairy foods are common sources of probiotics. These include:

  • yogurt
  • cottage cheese
  • sauerkraut
  • kefir
  • kombucha
  • pickled vegetables
  • fermented soy products, including tempeh, miso, and natto

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Click here to learn more about vegan probiotic options.

Probiotic supplements

People can also take probiotic supplements, which come in various levels of different strains. These are typically available in capsule form.

Supplements are a simple way to get large amounts of healthy microbes into the body. However, it is important that people follow the instructions and take the correct dosage.

Probiotics may have several benefits due to how they interact with the body. While they may affect many systems and organs, the main advantages of probiotic use focus on aiding gut flora and digestive health.

A study in Medicine notes that they may play a role in several digestive issues, such as:

However, the study researchers call for more long-term research into chronic digestive conditions, as there is limited evidence to make any claims about probiotic use.

A 2018 review notes the benefits of taking probiotics :

  • overall gut bacteria
  • immune system health
  • bowel movements
  • stool consistency
  • vaginal health

It is important to note that these effects persist for as long as the person takes probiotics. Also, there is limited evidence discussing the long-term benefits, so more research is necessary.

Probiotics are generally safe. However, taking them in large doses may cause minor symptoms in some people, such as gas or bloating.

There are some rare side effects associated with probiotics, generally where the person has underlying issues.

These side effects include:

People who are critically ill or have conditions that compromise their immune system should not take probiotics. Additionally, the potential risks of probiotic use in pregnant or breastfeeding people are not well-understood.

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Probiotics are live microbes that may positively influence the body. They may help improve markers of digestive health, reduce symptoms of some digestive conditions, and improve the immune system.

For short-term symptom relief, such as reducing diarrhea, some probiotics may work in as little as a few days. For chronic conditions or general immune health, it may be most beneficial to take probiotics for weeks or months at a time.

Most people can tolerate probiotics well, and they can help restore or balance the healthy gut microbiome. However, some may wish to discuss probiotics with their doctor before they incorporate them into their diet.