Does taking probiotics with antibiotics prevent diarrhea?
Yes, but the effect depends on how you define 'diarrhea' and which probiotic you use. The most rigorous study here — a randomized, quadruple-blind, placebo-controlled trial in 350 children — tested a multispecies probiotic (10 billion CFU daily) during and for 7 days after antibiotics. It found no statistically significant reduction in the most stringent definition of antibiotic-associated diarrhea (AAD), which required three or more loose stools in 24 hours and testing for C. diff and other pathogens (relative risk 0.81, 95% CI 0.49–1.33) [1]. However, when the researchers looked at diarrhea from any cause, the probiotic group had a 35% lower risk (relative risk 0.65, 95% CI 0.44–0.94) [1]. This suggests probiotics can reduce overall diarrhea episodes, even if they don't prevent the most severe, lab-confirmed cases.
A 2022 review of multiple trials and meta-analyses agrees that probiotics — especially Lactobacillus and Saccharomyces strains — are beneficial for preventing AAD, though it notes that adverse events have been reported and that probiotics are generally considered safe and inexpensive [5]. The takeaway: probiotics can help with loose stools during antibiotics, but they are not a cure-all.
Do probiotics protect your gut microbiome during antibiotics?
Surprisingly, the evidence says no — probiotics do not meaningfully preserve the diversity of your gut bacteria while you're on antibiotics. A 2023 systematic review and meta-analysis of 15 randomized controlled trials (with 5 included in the meta-analysis) found no significant difference in key diversity measures (Shannon index, Chao1, observed OTUs) between people who took probiotics alongside antibiotics and those who took a placebo [4]. The authors concluded that 'probiotic supplementation during antibiotic therapy was not found to be influential on gut microbiome diversity indices' [4]. This is important because a diverse microbiome is linked to better immune function and lower infection risk. So while probiotics may ease diarrhea, they don't seem to restore the microbial balance that antibiotics disrupt.
A 2025 review echoes this, noting that a separate meta-analysis by Matuskova et al. also found that probiotics do not significantly prevent the reduction of gut microbiota diversity caused by antibiotics [6]. This means that if your goal is to maintain a healthy gut ecosystem during treatment, probiotics alone may not be enough.
Can probiotics reduce the risk of a serious infection?
The evidence is mixed and context-dependent. In one study of 104 men with prostate gland infections (MAGI), those who took a specific probiotic combination (Enterococcus faecium and Saccharomyces boulardii during antibiotics, then Lactobacilli) had a significantly higher rate of infection eradication: 76.2% versus 50% with antibiotics alone (p < 0.05) [3]. This suggests that in certain urogenital infections, probiotics can help clear the infection, not just prevent diarrhea.
However, for the most feared complication of antibiotics — C. difficile infection — the large pediatric trial found no benefit: the probiotic did not reduce the risk of C. diff-associated diarrhea [1]. And a 2022 review on bronchiectasis (a lung condition) warns that reducing inflammation with certain drugs can actually increase infection risk, though it does not directly test probiotics [2]. The bottom line: probiotics may help clear some specific infections (like prostate infections), but they do not appear to prevent C. diff or other serious infections in the general population.
About These Sources
This answer is built on 6 peer-reviewed studies — published from 2022 to 2025, 1 from 2024 or later, 4 in Q1 journals, collectively cited 213 times — selected as the most relevant from 6 studies that passed quality screening, drawn from 36 papers retrieved from a database of over 500 million.
Sources used in this answer
Multispecies Probiotic for the Prevention of Antibiotic-Associated Diarrhea in Children
In a randomized, quadruple-blind, placebo-controlled trial of 350 children, a multispecies probiotic did not reduce the most stringently defined antibiotic-associated diarrhea (AAD) but did lower overall diarrhea risk by 35% (RR 0.65, 95% CI 0.44–0.94) [1].
Bronchiectasis enters the inflammation era
A review on bronchiectasis discusses that reducing neutrophilic inflammation can increase infection risk, but does not directly test probiotics; it highlights the complexity of targeting inflammation in chronic lung disease [2].
Association of Probiotic Treatment With Antibiotics in Male Accessory Gland Infections
In 104 men with prostate gland infections, adding a specific probiotic (Enterococcus faecium and Saccharomyces boulardii) to antibiotics led to a significantly higher infection eradication rate (76.2% vs 50%, p < 0.05) [3].
Probiotic supplementation during antibiotic treatment is unjustified in maintaining the gut microbiome diversity: a systematic review and meta-analysis
A systematic review and meta-analysis of 15 RCTs found no significant difference in gut microbiome diversity (Shannon, Chao1, observed OTUs) between those taking probiotics with antibiotics and those taking placebo [4].
Probiotics for the Prevention of Antibiotic-Associated Diarrhea
A review of multiple trials and meta-analyses concludes that probiotics, especially Lactobacillus and Saccharomyces strains, are beneficial for preventing antibiotic-associated diarrhea and are generally safe and inexpensive [5].
Probiotics as Support for Antibiotic Therapy: Benefits and Risks
A 2025 review notes that while probiotics may reduce AAD risk, they do not significantly prevent antibiotic-induced loss of gut microbiome diversity, and there are concerns about transfer of antibiotic resistance genes [6].