How Long Does It Take For Probiotics To Work?

  • 1st Revision:Tan Jit Yih

Probiotics are advertised as effective for maintaining health, preventing and treating some diseases. There are different probiotics out there but not enough guidance on what probiotic to take and for how long. 

How long you should take any probiotic will depend on:

  • Why you’re taking it—the condition you hope to manage
  • What probiotic you’re using—the particular probiotic strain

You may experience some benefits after 1 week of using a probiotic or after months. To make sure probiotics work for you, you should understand why they are effective and know how to choose the right one.    

Understanding probiotics

Probiotics are live microorganisms (mostly bacteria and yeasts) that have health benefits when ingested or applied to the body, adequately.1,2 

It may sound strange to consume microorganisms for health benefits. But humans host millions of microorganisms all over the body—in the gut, vagina, nose and on the skin. Collectively, these microorganisms form the human microbiota. These microorganisms can be affected by diet, illnesses, use of antibiotics or other drugs, or interactions with people or animals. Some of these microorganisms are potentially harmful but most are good or friendly. They help protect the body from harmful microorganisms, regulate mood, and aid digestion and growth.3

Probiotics, too, are good or friendly. They help restore the balance of the body’s microorganisms which can be disrupted by illnesses or certain treatments.4

Types of probiotics

Currently, most commercially available probiotics come from the bacterial genera: 

  • Bifidobacterium
  • Lactobacillus and
  • Saccharomyces, a yeast genus

Less common probiotics come from these bacterial genera:

  • Bacillus
  • Propionibacterium
  • Enterococcus
  • Pediococcus
  • Streptococcus and
  • Escherichia2,5

In biological classification, a genus (plural genera) consists of different closely related species of an organism. And within a species, there may be variants known as strains. It’s good to know this because probiotics are usually identified using their genus followed by species and strain names. 

Where do we get probiotics?

Probiotics are usually taken orally, through the vagina or applied on the skin. You can get probiotics in different formulations depending on your country. These include 

  • Foods: Fermented foods (like yoghurt) are good sources of probiotics as they contain live microorganisms. But some fermented foods may have their live microorganisms removed during the production process or the microorganisms may not be effective. Probiotics are also added to unfermented foods like milk, formulas, cereals, nutrition bars, smoothies and juices.5 To know if a particular food contains any probiotic, you should check the label
  • Dietary or nutritional supplements: You can find probiotic supplements as drinks, powders or capsules. Probiotic supplements usually come as a mixture of multiple strains of microorganisms but you might also find single strains5
  • Medical devices: You can use probiotics with some medical devices6
  • Drugs: Some probiotics are available as drugs. These drugs are usually subjected to the regulations and approvals other drugs require. The safety and effectiveness of probiotic drugs are usually tested before and after marketing7

Health Benefits

Probiotics have generalised health benefits and benefits associated with the strain or species of microorganisms in the product. Probiotics produce health benefits because they:

  • Produce substances that prevent harmful microorganisms from settling in our body, aid digestion and provide other benefits
  • Improve the function of your body’s microorganisms
  • Inhibit the growth of harmful microorganisms
  • Improve immunity
  • Improve the function of the epithelium—the barrier against foreign substances
  • Reduce the pH of the gut
  • Neutralise toxins
  • Synthesise vitamins
  • Affect hormone and nervous systems2,5 

Different strains of probiotics can reduce the risk of or help in the treatment of specific health conditions: 

How long does it take for probiotics to work?

For a probiotic to work, you must take it in sufficient amounts (i.e., the recommended dose). The length of time you must take a probiotic for it to work depends on the disease you are treating or preventing, and the probiotic you use. So, you might use a probiotic for 1 week and observe some effects and you might need to take probiotics for months. You might also need to use a probiotic long term if you desire continuous benefits. This is because probiotics don’t stay in the body long after you’ve stopped using them.

To get an idea of how long you should use a probiotic, let’s look at how long participants took probiotics to observe benefits in research studies.

  • For antibiotic associated diarrhoea, taking probiotics for 1 week reduced the chance of getting diarrhoea
  • Irritable bowel syndrome patients started to feel some pain relief after using probiotics for 14 days
  • Probiotics used to prevent flare-ups of ulcerative colitis were used for up to 12 months (This is usually the case for drugs used to prevent ulcerative colitis flare-ups as they can be taken for years.) 
  • Symptoms of eczema improved after 2 months of probiotic use8

Since the probiotic strain you use may be different, it might take a shorter or longer time to observe benefits. Generally, if you don’t observe any benefits after using a probiotic for about a month, that probiotic might not be right for you.9  

What to do if your probiotics are not working?

A particular probiotic strain may not benefit everyone. This may be due to individual differences like diet, gut microorganisms, current medications and the fact that every body is different.9 

If you have been using a probiotic according to the manufacturer's instructions for a while and you don’t see any benefits, you could check to see if there’s a more appropriate probiotic for you. It could be that you are using the wrong strain. Most probiotic strains that work for a particular disease may not treat other diseases. The strains that effectively treat a disease might not prevent the same disease. Also, some strains might not be effective for both adults and children. To select an appropriate product, pay attention to the information on the product label and the promised health benefits. You can also ask your doctor for advice to choose a product that’s best for your condition. 

Another thing you can do is to try a different brand. Some brands produce low quality probiotics. It may be that the strains stated on their labels are not actually contained in the product, orr the quantity of the strains might not be enough to produce the promised health benefits. You can opt for products by more reputable brands or dig around for reviews by independent organisations or customers before using a product.10

You may also benefit from changing the formulation you are using. Probiotics exist in many formulations from fermented yoghurts to supplements in capsules. There’s not much research on how probiotic formulations impact their effectiveness. But, it’s possible that the formulation you are using might not be as effective. It could be that the benefit you desire isn’t offered in that formulation, or the microorganisms might be destroyed by your gut in some formulations. Moreover, certain products need special storage and handling. If they are not handled properly, the may not be effective.7,10 

You can ask your doctor to help you find another probiotic if you feel like the one you are currently using isn’t working. 

Choosing the right probiotic for you

You can keep these things in mind to choose the right probiotic product:

  • You should have specific goals before using probiotics. (Do you want to solve a health problem? Or do you want to improve your health?). This is because different probiotics have different benefits
  • Probiotic product labels should state the possible health benefits of using their product based on scientific evidence. These should align with your goals
  • The dose or quantity you should use for any health benefit should be stated
  • Probiotic products should identify probiotics according to their genus (e.g Lactobacillus), species (e.g rhamnosus) and, if applicable, their strain (e.g GG). The genus is sometimes shortened to the first letter. It’s not enough to simply state the genus or any unusual name like “live probiotic”, “lactic ferment” or “active bifidus”. You should use such products with caution. You can use this tool to validate scientific names
  • You might notice multiple strains in a probiotic product. This does not necessarily mean the product has more health benefits. It could be that the combination of strains provides health benefits
  • When multiple strains are used, the product should state the health benefits and whether these benefits come from individual strains or the blend of strains. Each strain should also be listed according to their amount in the product
  • You should take note of the “end of shelf life” date (expiration date). At this date, probiotics lose their viabilitybecause many of the microorganisms would be dead (and they need to be alive to work)
  • The minimum number of probiotic strains alive at the end of shelf life (not at the manufacturing date) should be stated. This number is expressed as colony forming units (CFUs). For multiple strains, the total number of CFUs should be stated. And if possible, the number of CFUs of each strain should be stated   
  • A higher number of CFUs does not mean the product is better. However, the number of CFUs at the end of shelf life must be enough to confer health benefits
  • The proper way to store a probiotic product should be stated. Most probiotics can be stored at room temperature while some require refrigeration
  • The product should list contact details on the label
  • Look out for a mark of safety by a relevant authority. In Europe, this would be a Qualified Presumption of Safety (QPS) badge by the EFSA. In the US, a Generally Recognised As Safe (GRAS) badge would be assigned by the FDA5,7,11,12  

It’s important that you ask for help from your doctor when choosing a probiotic especially if you have a health condition. 

Risk factors

Probiotics are used by many people and are generally considered safe especially for healthy people. However, there is a higher risk of harm in people with severe illnesses or a weak immune system (such as premature infants, HIV patients, cancer patients). These people need special attention while taking probiotics. The potential harmful effects of probiotics include:

  • Infections
  • Production of harmful substances by probiotics
  • Making harmful microorganisms resistant to antibiotics
  • Risk of harmful substances contaminating probiotics during their manufacture and handling1,2 

If you choose the right probiotic with the help of your doctor, you would reduce these risks.

When to seek medical attention

You shouldn’t use probiotics (or any other supplement) to self-treat any medical condition. You should always consult your doctor for proper advice, direction and monitoring while using probiotics.1 You may experience mild stomach upset, bloating or flatulence when you use probiotics. If you experience any unusual or unbearable side effects,contact your doctor for a proper evaluation.


Probiotics are live microorganisms that have health benefits when taken in adequate amounts. The duration you need to take them for their health benefits will depend on the probiotic you use and the benefit you wish to get. You should choose a good probiotic and use it for about a month to see if it’s right for you.


  1. Probiotics: what you need to know [Internet]. NCCIH. [cited 2022 Oct 12]. Available from: 
  2. Probiotics [Internet]. International Scientific Association for Probiotics and Prebiotics (ISAPP). [cited 2022 Oct 12]. Available from: 
  3. We are never alone: living with the human microbiota [Internet]. Frontiers for Young Minds. [cited 2022 Oct 12]. Available from: 
  4. Probiotics [Internet]. 2017 [cited 2022 Oct 12]. Available from: 
  5. Office of dietary supplements - probiotics [Internet]. [cited 2022 Oct 12]. Available from: 
  6. Verrucci M, Iacobino A, Fattorini L, Marcoaldi R, Maggio A, Piccaro G. Use of probiotics in medical devices applied to some common pathologies. Ann Ist Super Sanita. 2019 Dec;55(4):380–5.
  7. Mazzantini D, Calvigioni M, Celandroni F, Lupetti A, Ghelardi E. Spotlight on the compositional quality of probiotic formulations marketed worldwide. Frontiers in Microbiology [Internet]. 2021 [cited 2022 Oct 12];12. Available from: 
  8. Islam SU. Clinical uses of probiotics. Medicine (Baltimore) [Internet]. 2016 Feb 8 [cited 2022 Oct 13];95(5):e2658. Available from: 
  9. Probiotics [Internet]. International Scientific Association for Probiotics and Prebiotics (ISAPP). [cited 2022 Oct 13]. Available from: 
  10. Sniffen JC, McFarland LV, Evans CT, Goldstein EJC. Choosing an appropriate probiotic product for your patient: An evidence-based practical guide. PLoS One [Internet]. 2018 Dec 26 [cited 2022 Oct 13];13(12):e0209205. Available from: 
  11. KC. Decoding a probiotic product label [Internet]. International Scientific Association for Probiotics and Prebiotics (ISAPP). 2022 [cited 2022 Oct 13]. Available from: 
  12. Quick guide to selecting the right probiotic strain | the probiotics institute by chr. Hansen inc. [Internet]. [cited 2022 Oct 13]. Available from: 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

Get our health newsletter

Get daily health and wellness advice from our medical team.
Your privacy is important to us. Any information you provide to this website may be placed by us on our servers. If you do not agree do not provide the information.

Roseline Akpa

Bachelor of Science degree in Human Physiology, Ahmadu Bello University, Nigeria

She is a freelance health writer interested in mental health, holistic health, and health tech.

Leave a Reply

Your email address will not be published. Required fields are marked * presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
Klarity / Managed Self Ltd
Alum House
5 Alum Chine Road
Westbourne Bournemouth BH4 8DT
VAT Number: 362 5758 74
Company Number: 10696687

Phone Number:

 +44 20 3239 9818