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Sure, probiotics are good for you, but how long do you have to take them to see results? And on a scale of 1 to superhuman, what kind of results are we talkin’ about?

How long does it take for probiotics to work?

That depends on a few things:

  • why you’re taking it
  • what type you’re taking
  • how much you’re taking

Results vary from person to person and may take anywhere from a few days to a few months.

What are probiotics, exactly?

They’re good-for-you live microbes — either yeast or bacteria. There are countless brands to choose from that contain healthy bacteria strains, or cultures, with fun scientific names like Lactobacillus and Bifidobacterium.

A word of caution

Probiotics aren’t reviewed by the FDA before they go on the market because they’re considered dietary supplements, food additives, or fermented foods. This means you don’t know exactly what you’re getting in terms of quality.

The strain and potency of the probiotics you’re using and the health condition you’re using them for are all important factors that can help you determine how long they’ll take to work — and if they’ll work at all.

For diarrhea…

A 2010 review of 63 studies found that combining rehydration therapy treatment with probiotics can reduce the duration and frequency of infectious diarrhea in as little as 2 days.

For gut health…

If you’re taking a probiotic for better immune or gut health, results may take longer.

A 2018 study found that people who swigged a high-dose Lactobacillus sp. probiotic drink for 12 weeks had fewer upper respiratory infections and flu-like symptoms than the placebo group. They also had better immunity indicators.

For irritable bowel syndrome…

In a 2011 study, people with irritable bowel syndrome (IBS) who took Saccharomyces boulardii for 4 weeks saw more symptom improvement than those who took a placebo.

For bloating…

In a 2014 study, participants who took a combination of probiotics saw significant improvements in bloating in as little as 21 days. And in a small 2011 study, those who took probiotics had improvements in bloating after 4 weeks, and their symptoms got even better by 8 weeks.

The effects of probiotics vary from person to person. Factors like your age, gut microbiome, genes, and diet will affect how well probiotics work for you and how long they’ll take to be effective.

A few reasons a probiotic may not work for you:

  1. You didn’t follow the directions. If the label says to take the pill with food, take it with food. And pay attention to the expiration date.
  2. You didn’t store them correctly. Like new relationships, probiotics are fragile. If they aren’t stored correctly — some have to stay in the fridge — the cultures may die.
  3. You got a crummy product. Not all products have live strains or enough CFUs to make it through manufacturing, storage, and your body’s digestive conditions to reach your intestines intact. Strain potency and live culture survival matter. Research suggests products with 5 billion CFUs or higher are more effective than lower doses for treating gastrointestinal conditions.
  4. You picked the wrong strain. Different cultures work on different ailments. Do your research and talk to your doctor to find out which strain is best for you.

When you’re hunting for the right probiotic, it’s important to know why you want to take one. Some people want to improve immunity or gut health, while others need relief from a specific symptom.

The trick is to find a product that contains strains known to help your specific issue. For instance, Lactobacillus, Bifidobacterium (bacteria), and Saccharomyces boulardii (yeast) are generally safe and helpful for conditions such as IBS, traveler’s and antibiotic-related diarrhea, eczema, and ulcerative colitis.

A review of 45 studies found probiotics to be helpful in healthy people who want to maintain gut, immune, and vaginal health.

Hoping to reap the benefits of popping probiotics?

Here’s what you can do to give yourself the best shot at good results:

  1. Pick a premium product. Get a probiotic with live cultures, because those determined strains have to survive your stomach and make it to your intestines to work. In other words, pay attention to the star ratings when you research products online.
  2. Take it as directed. Follow the label’s directions on what time of day to take the probiotic and whether to take it with or without food.
  3. Be timely. Pay attention to the expiration date. Bottles often include a “use by” date, which will indicate how long the cultures will stay live. There’s no use in taking probiotics with strains that are dead. Skip a product that lists its expiration as the “time of manufacture” because the cultures may not be active — or there may not be as many of them by the time you buy it.
  4. Store the container correctly. If it needs to be refrigerated, don’t leave it on the kitchen counter.
  5. Watch added ingredients. Make sure the probiotic doesn’t have extra ingredients that are known to interact with any medications or cause other reactions in your body.

Remember: Probiotics aren’t guaranteed to work. They may even be harmful in some cases. A 2018 review of several hundred trials found that researchers often neglected to report negative effects from using probiotics, prebiotics, and synbiotics.

The best way to know if you should take a probiotic is to chat with your doctor. They can determine if taking a probiotic will benefit you and which strain or brand is your best bet.

Probiotics typically take anywhere from a few days to several weeks to work. And sometimes they may not do anything.

Here’s how you might be able to improve their effectiveness:

  • Select a strain(s) that’s shown to improve your specific symptoms or to improve overall health.
  • Follow the directions to be sure you’re taking it correctly.
  • Choose a product with live cultures — and enough of them.