Yes, you can take probiotics with antibiotics, and doing so can significantly reduce your risk of antibiotic-related digestive problems. Pooled data from clinical trials shows that people who take probiotics alongside antibiotics cut their risk of antibiotic-associated diarrhea by about 39%, with roughly 1 in 11 patients experiencing a clear benefit. The key is choosing the right strain, timing your doses properly, and continuing long enough.
Why Antibiotics Disrupt Your Gut
Antibiotics don’t distinguish between harmful bacteria and the beneficial species living in your digestive tract. A course of antibiotics can wipe out large portions of your gut community, creating gaps that allow problematic organisms to flourish. The most common result is diarrhea, which affects anywhere from 5% to 35% of people on antibiotics depending on the drug.
The more serious risk is a Clostridioides difficile (C. diff) infection, which thrives when antibiotics clear out competing bacteria. C. diff causes severe, sometimes life-threatening diarrhea and is a particular concern for hospitalized patients and older adults.
How Probiotics Help During Antibiotic Treatment
Probiotics work through several overlapping mechanisms. They compete with harmful organisms for nutrients, starving out potential invaders before they gain a foothold. They also stimulate the gut lining to produce protective mucus, which makes it harder for pathogens to attach to intestinal walls. On the immune side, probiotics help regulate the body’s inflammatory responses, keeping the immune system active without overreacting.
These effects translate into real clinical outcomes. A meta-analysis of 19 randomized controlled trials covering more than 6,200 hospitalized patients found that probiotic use reduced the risk of C. diff infection by roughly 58%. The protection was even stronger when probiotics were started within the first one to two days of antibiotic therapy, cutting C. diff risk by 68%.
Which Strains Work Best
Not all probiotics are interchangeable. Two strains stand out with the strongest evidence for use during antibiotic courses: Lactobacillus rhamnosus GG (often labeled LGG) and Saccharomyces boulardii.
LGG is one of the most studied bacterial probiotics. Across 12 randomized trials involving nearly 1,500 participants, it cut the rate of antibiotic-associated diarrhea roughly in half, from about 22% to 12%. The evidence is particularly strong in children. In trials with pediatric patients, diarrhea rates dropped from 23% in the placebo group to under 10% in children given LGG.
Saccharomyces boulardii has a unique advantage: it’s a yeast, not a bacterium, so antibiotics don’t kill it. That means it keeps working at full strength regardless of which antibiotic you’re taking. In a real-world study of patients on concurrent antibiotics, 77% of those taking S. boulardii were free of diarrhea at follow-up, compared to just 18% in the control group. Among children, six trials covering more than 1,600 kids showed S. boulardii reduced diarrhea incidence from about 21% to 9%.
Multi-strain combinations that include Bifidobacterium and Streptococcus thermophilus have also shown benefit, though the evidence base is smaller.
Timing and Spacing Your Doses
Because most bacterial probiotics are vulnerable to antibiotics, spacing matters. The International Scientific Association for Probiotics and Prebiotics recommends leaving at least a two-hour gap between your antibiotic dose and your probiotic dose. This reduces the chance that the antibiotic will kill the probiotic organisms before they reach your gut.
If you’re taking S. boulardii, timing is less critical since antibiotics don’t affect yeast. You can take it at any point relative to your antibiotic dose without losing effectiveness.
Starting early makes a meaningful difference. The data on C. diff prevention shows significantly greater risk reduction when probiotics begin within the first one to two days of antibiotic treatment, rather than later in the course. Don’t wait for symptoms to appear.
How Much to Take and For How Long
Dose matters more than many people realize. A 2019 Cochrane review of 33 trials found that higher doses, in the range of 5 to 40 billion colony-forming units (CFUs) per day, were significantly more effective than lower doses. For LGG specifically, a dose of 10 to 20 billion CFUs per day achieved a 71% reduction in diarrhea, while 3 billion CFUs per day only achieved a 34% reduction.
The European Society for Pediatric Gastroenterology, Hepatology and Nutrition suggests 10 to 20 billion CFUs per day of LGG, or 250 to 500 mg (about 5 to 10 billion CFUs) of S. boulardii. These ranges apply to both adults and children.
You should continue taking the probiotic for at least the full duration of your antibiotic course. Many practitioners suggest continuing for an additional one to two weeks after finishing antibiotics, since your gut flora remains disrupted and vulnerable during that recovery period. Starting probiotics more than a week into an antibiotic course appears to reduce their effectiveness.
Probiotics for Children on Antibiotics
Children are especially prone to antibiotic-associated diarrhea, and the evidence for probiotics in pediatric patients is strong. The European Society for Pediatric Gastroenterology reviewed 21 trials involving more than 3,200 children and specifically recommended LGG and S. boulardii as the two strains with sufficient evidence for preventing diarrhea in kids on antibiotics.
In these studies, the number needed to treat was as low as 6, meaning for every 6 children given a high-dose probiotic during antibiotics, one case of diarrhea was prevented that would have otherwise occurred. Look for child-appropriate formulations (sachets, drops, or chewables) that contain one of these two strains at adequate doses.
Who Should Be Cautious
Probiotics are safe for the vast majority of people, but there are exceptions. Individuals with severely compromised immune systems, including those undergoing cancer treatment, organ transplant recipients, and people with conditions that compromise the intestinal barrier, face a small but real risk that probiotic organisms could enter the bloodstream and cause serious infections such as sepsis or endocarditis. In these populations, probiotic strains can behave as opportunistic pathogens rather than helpful guests.
Premature newborns and critically ill patients in intensive care also fall into higher-risk categories. If you have a condition that significantly weakens your immune system, the decision to use probiotics during antibiotic therapy should involve your treatment team weighing the gut benefits against the infection risk.
For otherwise healthy adults and children, side effects are typically limited to mild gas or bloating in the first day or two, which usually resolves on its own as the gut adjusts.