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Probiotics for Antibiotic Diarrhoea: What the Evidence Shows

Probiotics taken alongside antibiotics can lower the chance of antibiotic-related diarrhoea, especially in children. Learn which types were studied, safety points and warning signs.

Edited by Anmar ArabPublished 16 October 2026, 7 min read
On this page
  1. Quick answer
  2. What the research says
  3. How to use it
  4. Possible side effects and interactions
  5. Who should avoid it
  6. When to see a doctor
  7. Frequently asked questions

Quick answer

Diarrhoea is one of the most common side effects of antibiotics. Mayo Clinic estimates that roughly one in five people taking antibiotics develop it, usually in a mild form that settles soon after the course ends.

Probiotics are live microorganisms, mostly bacteria such as Lactobacillus and Bifidobacterium or the yeast Saccharomyces boulardii, taken as supplements or in some foods. Taking them alongside antibiotics appears to lower the chance of developing diarrhoea:

  • In children, a Cochrane review found diarrhoea in about 8% of those given probiotics compared with 19% of those who were not.
  • In adults and children taking antibiotics, probiotics reduced diarrhoea caused by C. difficile, a more serious gut infection, mainly in people already at higher risk.
  • Probiotics appear safe for most healthy people, but they are not suitable for people who are seriously ill, have a weakened immune system, or for premature babies.

The benefit depends on the specific strain and dose, and experts still cannot say which product is best.

What the research says

Children. A 2019 Cochrane review pooled 33 trials involving 6,352 children aged from a few days to 17 years who were taking antibiotics. Diarrhoea developed in 8% of children given probiotics and 19% of those given placebo or nothing, which the authors rated as moderate-certainty evidence. Roughly nine children needed to take probiotics to prevent one case. Higher doses, of at least 5 billion colony-forming units (CFU) a day, seemed to work better than lower ones. Based on these results, the review authors suggested Lactobacillus rhamnosus or Saccharomyces boulardii at 5 to 40 billion CFU a day as the most appropriate choices, while noting the high-dose finding still needs confirming in a large trial. Probiotics also shortened diarrhoea by about a day when it did occur, though this finding was less certain.

Adults. The US National Center for Complementary and Integrative Health (NCCIH) summarises reviews in adults. One review of 17 studies in people not in hospital found probiotics were linked to about half the likelihood of antibiotic-associated diarrhoea, although the authors called this tentative because study quality was moderate. Another review of 30 studies found a benefit in young and middle-aged adults, but no clear benefit was shown in people over 65, possibly because too few studies included them.

C. difficile diarrhoea. Clostridioides difficile (C. diff) can cause severe diarrhoea after antibiotics, particularly in hospitals and care homes. A 2025 Cochrane review found that in the main analysis of 31 trials, C. diff diarrhoea occurred in 1.5% of people given probiotics and 4.0% of those who were not, a moderate-certainty result. The benefit was concentrated in people whose baseline risk was above 5%. Where the risk was low, no difference was found, and the two largest trials did not show a clear benefit. The review could not say which probiotic works best, because no trials compared products directly.

Why strain matters. NCCIH stresses that probiotics are not interchangeable: a result for one Lactobacillus strain does not mean another strain, or a Bifidobacterium product, will behave the same way. For most uses, the best type, dose and duration are still unknown.

How to use it

If you would like to try probiotics during a course of antibiotics:

  1. Keep taking your antibiotic exactly as prescribed. Probiotics are an add-on, never a reason to stop or shorten the course.
  2. Choose a product that names the strain, not just the species. The children's review pointed to Lactobacillus rhamnosus and Saccharomyces boulardii.
  3. Look at the dose. The children's review found better results at 5 billion CFU a day or more, and suggested 5 to 40 billion CFU a day.
  4. Start with the antibiotic course and follow the product label for how long to continue. Trials gave probiotics alongside antibiotics, and NCCIH notes that the most useful duration is still uncertain.
  5. Ask a pharmacist to help you pick a product and check how to time it around your antibiotic doses, since advice depends on the product.

Foods. Yoghurt and other fermented foods can contain live cultures, but the trials described here tested specific probiotic products. Because effects are strain-specific, the results cannot be assumed to apply to any food.

Other sensible steps. Mayo Clinic advises taking antibiotics only when needed (they do not work against colds and flu), washing hands often, and telling your doctor if you have had antibiotic-associated diarrhoea or C. diff before, as a different antibiotic may be chosen. If diarrhoea does start, drink plenty of fluids to avoid dehydration.

Probiotics are not safe for everyone. Do not give them to premature babies, and do not use them if you are seriously ill or have a weakened immune system unless your doctor recommends them, because the risk of serious harm, including severe infections, is higher in these groups.

Possible side effects and interactions

For most healthy people, probiotics cause few problems. In the children's Cochrane review, no serious side effects were linked to probiotics, and minor complaints such as rash, nausea, wind, bloating and constipation were reported. In the 2025 review, mild problems like cramping, nausea and soft stools were seen at similar or lower rates than in comparison groups.

NCCIH notes that few studies have looked closely at safety, and possible harms include:

  • Infections caused by the probiotic organisms themselves, mainly in vulnerable people
  • Harmful substances produced by the microorganisms
  • Transfer of antibiotic resistance genes to other gut bacteria
  • Contamination: some products have been found to contain microorganisms not listed on the label, occasionally posing serious risks

In the United States, many probiotics are sold as dietary supplements, which do not need approval before going on sale, so quality varies between brands.

Who should avoid it

Talk to a doctor before taking probiotics if you:

  • Have a weakened immune system, for example from chemotherapy
  • Are seriously ill, including being a seriously ill hospital patient
  • Are caring for a premature baby: the US Food and Drug Administration has warned that these babies face a risk of severe, potentially fatal infections from probiotic products

In trials, otherwise healthy children had no serious side effects from probiotics, but check with a doctor or pharmacist before giving them to a baby or young child.

When to see a doctor

Mild antibiotic-related diarrhoea often settles on its own. Contact a doctor if you have:

  • Diarrhoea lasting more than two days
  • Blood in your stool, black or tarry stools, or bleeding from the bottom
  • Fever, stomach pain or cramping alongside diarrhoea
  • Signs of dehydration: extreme thirst, little or dark urine, dizziness or sunken eyes; in young children, no wet nappies for three hours or more, no tears or unusual drowsiness
  • Diarrhoea that starts days or weeks into or after a course, since serious cases can begin up to about two months after starting antibiotics
  • Diarrhoea while taking antibiotics if you are over 65, have had C. diff before, take stomach-acid medicines such as omeprazole, or have a weakened immune system

The NHS advises getting urgent advice for diarrhoea during or soon after antibiotics, bloody diarrhoea, or diarrhoea lasting more than seven days.

Frequently asked questions

Can I take probiotics at the same time as antibiotics?

Trials gave probiotics during the antibiotic course. Because products differ, ask your pharmacist how to space them around your antibiotic doses, and follow the label.

Which antibiotics most often cause diarrhoea?

Mayo Clinic lists cephalosporins, fluoroquinolones, penicillins, clindamycin, carbapenems and macrolides among those most often linked to diarrhoea, though almost any antibiotic can cause it. Never stop a prescribed antibiotic without talking to your doctor.

Do probiotics help older adults?

The evidence is less clear. One review found benefit in young and middle-aged adults but could not show it in people over 65, partly because few studies included them. Older adults are also at higher risk of C. diff, so any diarrhoea on antibiotics should be checked by a doctor.

Is yoghurt enough?

Yoghurt can be part of a healthy diet, but the studies used specific probiotic strains at measured doses. Whether a particular yoghurt gives the same effect is unknown.

References

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