Can I Take Amoxicillin With Probiotics?

Taking probiotics alongside amoxicillin is safe for most people, and a direct pharmacokinetic study has confirmed that one of the most studied probiotic strains does not change how your body absorbs the antibiotic. The more interesting question is whether probiotics actually help during an amoxicillin course, and which types survive it. The answer depends on the kind of probiotic, the person taking it, and what you mean by “help.”

What Amoxicillin Does to Your Gut

Amoxicillin is a broad-spectrum penicillin, which means it does not limit itself to whatever infection your doctor prescribed it for. It sweeps through the bacteria in your gut on its way through your digestive tract, reducing both the variety of species present and their overall abundance. A study tracking microbiome changes during amoxicillin treatment found significant drops in bacterial diversity, richness, and evenness, though these measures began reverting after the course ended.¹ Animal research has reinforced this picture, showing that oral amoxicillin reduces archaeal load and shifts bacterial composition in the gut.²

In children, the disruption can be sharp. A study of children receiving amoxicillin found that gut species richness dropped from about 38 species at baseline to about 28 after one week, and Proteobacteria, a phylum that includes many opportunistic pathogens, roughly doubled in relative abundance from around 13% to 27%.³ This kind of upheaval is what sets the stage for antibiotic-associated diarrhea, the most common side effect that sends people looking for probiotics in the first place. The disruption of normal gut flora, especially Lactobacillus species, can lead to diarrhea and related digestive disturbances.⁴

Bacterial Probiotics vs. Yeast Probiotics Under Amoxicillin

This is where many people run into confusion. Amoxicillin kills bacteria. Most probiotics are bacteria. So how is taking a bacterial probiotic alongside an antibiotic supposed to work? The honest answer is that it is a bit of a paradox, and sensitivity testing confirms it: bacterial probiotics are generally susceptible to most commonly prescribed oral antibiotics, while yeast-based probiotics like Saccharomyces boulardii are naturally resistant.⁵

That distinction matters practically. Saccharomyces boulardii, a yeast, passes through your system unaffected by amoxicillin because the drug targets bacterial cell walls, which yeast cells lack. Bacterial strains like Lactobacillus rhamnosus GG are susceptible to penicillins, so a large fraction of those organisms will be killed by the amoxicillin in your gut. This does not necessarily mean bacterial probiotics are useless during a course, but it does mean that their survival is compromised. Some researchers have specifically flagged that LGG’s sensitivity to penicillin might limit its effectiveness when co-administered with amoxicillin or amoxicillin-clavulanate.⁶

Despite that vulnerability, bacterial probiotics can still pass through the gut in large enough numbers to exert some benefit, particularly if timing is staggered. And some spore-forming bacteria, such as Bacillus clausii, can survive antibiotic exposure better than non-spore-forming strains because their dormant spore form resists the drug’s mechanism of action. An animal study found that B. clausii supplementation during amoxicillin treatment mitigated oxidative stress caused by the antibiotic.⁷ Still, the strongest evidence for co-administration with antibiotics points to S. boulardii, precisely because it is immune to the drug.

Does Taking a Probiotic Actually Prevent Diarrhea?

The evidence here is reasonably strong, especially for S. boulardii. A large meta-analysis of randomized controlled trials found that this yeast probiotic cut the risk of antibiotic-associated diarrhea roughly in half, dropping it from about 19% in control groups to about 9% in those taking the probiotic. The benefit held for both children and adults across more than 20 trials.⁸ A separate meta-analysis in adults reached a nearly identical conclusion.⁹

For bacterial strains, the picture is more mixed. A trial testing a combination of Lactobacillus helveticus and Lactobacillus rhamnosus in healthy adults taking antibiotics found that while the probiotic group still experienced diarrhea-like episodes, those episodes were shorter, averaging about 2.7 days compared with 3.7 days in the placebo group.¹⁰ So even when bacterial probiotics do not prevent diarrhea entirely, they may shorten how long it lasts. A pediatric trial using a multi-strain probiotic yogurt containing LGG, L. acidophilus, and Bifidobacterium found a more dramatic effect: no cases of severe diarrhea in the probiotic group compared with six in the placebo group, and far fewer episodes of minor diarrhea.¹¹

One pediatric trial of Bifidobacterium breve PRL2020, a strain specifically selected for resistance to amoxicillin and amoxicillin-clavulanate, reported that diarrhea incidence dropped by about 70% in children receiving the probiotic alongside their antibiotic course.¹² The detail that this strain was pre-screened for amoxicillin resistance underscores the point: not all bacterial probiotics are equal, and the ones most likely to help are those that can survive in the presence of the specific antibiotic being used.

Will a Probiotic Make Amoxicillin Less Effective?

This is the concern that stops many people from trying. The short answer is no. A pharmacokinetic study specifically tested whether Saccharomyces boulardii CNCM I-745 altered amoxicillin’s absorption and found no significant differences in any measured parameter: half-life, peak blood concentration, total drug exposure, time to reach peak levels, or elimination rate.¹³ Your body absorbs the antibiotic just as effectively whether or not you are taking a probiotic alongside it.

This makes biological sense. Probiotics work in the gut lumen and on the intestinal lining. Amoxicillin is absorbed into the bloodstream from the upper small intestine. The two operate in overlapping but functionally different spaces, and the probiotic organisms are not binding or inactivating the antibiotic molecules. There is no plausible mechanism by which a standard probiotic dose would reduce amoxicillin’s ability to reach its target infection.

How Probiotics Protect the Gut Lining

Beyond simply replenishing bacteria that amoxicillin has killed, probiotics appear to help by reinforcing the physical barrier of the intestinal wall. The gut lining is held together by tight junction proteins, microscopic structures that control what passes between cells. Both lab and animal studies show that several probiotic strains promote the production and proper placement of these tight junction proteins, strengthening the intestinal barrier.¹⁴ Probiotics also release bioactive compounds that trigger cell signaling pathways involved in maintaining barrier integrity, and they can prevent disruption of tight junctions by harmful agents.¹⁵

This barrier-protection effect is one reason probiotics can reduce diarrhea even when the probiotic organisms themselves are being killed by the antibiotic. Enough of them survive transit through the gut, even briefly, to interact with the intestinal wall and trigger protective responses before the antibiotic catches up to them. The benefit is not purely about populating the gut with new bacteria; it is partly about the chemical signals the probiotics release along the way.

The Recovery Debate

A 2018 study published in Cell introduced a complication. Researchers gave healthy volunteers a cocktail of antibiotics, then assigned them to recover naturally, take a standard multi-strain probiotic, or receive a transplant of their own pre-antibiotic stool. The probiotic group showed a markedly delayed and persistently incomplete return to their normal microbiome compared to both the natural recovery group and the stool transplant group.¹⁶

This study got a lot of attention and is worth understanding in context. The antibiotic regimen used was far more aggressive than a standard amoxicillin course: participants received a combination of multiple broad-spectrum antibiotics designed to wipe out gut flora as thoroughly as possible. And the probiotics were given after the antibiotics, not alongside them. The finding suggests that flooding the gut with a few dominant probiotic strains after heavy antibiotic depletion can crowd out the native species trying to recolonize, essentially occupying the ecological niches those species need. Whether this applies to someone taking a standard five-to-ten-day course of amoxicillin with a modest probiotic dose is far less clear. Most clinical trials of concurrent probiotic use during amoxicillin treatment have not reported delayed recovery as an outcome, and the diarrhea-prevention benefits observed in those trials suggest a net positive during the course itself.

The practical takeaway is that probiotics are best supported by evidence for use during the antibiotic course rather than for weeks afterward. If your gut is functioning normally after you finish amoxicillin, there is limited evidence that continuing probiotics long-term will speed recovery, and some reason to think it could slow the return of your native microbial community.

Timing Your Doses

If you are using a yeast-based probiotic like S. boulardii, timing relative to your amoxicillin dose does not matter much since the antibiotic cannot kill it. For bacterial probiotics, spacing makes more sense. Taking the probiotic at least two hours away from your amoxicillin dose gives the probiotic organisms some time in the gut before the next antibiotic wave arrives. This is not a hard rule backed by rigorous dose-timing trials, but it follows logically from what we know about how quickly amoxicillin reaches the gut after ingestion.

Most clinical trials that showed benefit had participants take the probiotic for the full duration of the antibiotic course, and some continued for a few days to a week afterward. The evidence does not support continuing probiotics for months post-antibiotics, and as noted above, doing so could theoretically slow microbiome recovery.

Children on Amoxicillin

Amoxicillin is one of the most commonly prescribed antibiotics for children, used for ear infections, strep throat, and respiratory infections. Children tend to be more susceptible to antibiotic-associated diarrhea than adults, in part because their gut microbiomes are still developing. The meta-analysis of S. boulardii found that the benefit was at least as strong in children as in adults, with diarrhea rates dropping from about 21% to about 9% in the pediatric trials.⁸

The probiotic yogurt trial mentioned earlier, which tested a combination of LGG, L. acidophilus, and Bifidobacterium in children on antibiotics, found striking results: zero cases of severe diarrhea in the probiotic group versus six in placebo, and just one episode of minor diarrhea versus 21. The probiotic group also reported fewer side effects overall.¹¹ Parents trying to get a child through an amoxicillin course with minimal digestive upset have reasonable evidence supporting probiotic use, whether as a supplement or as a probiotic-enriched yogurt.

Safety Concerns and Who Should Be Cautious

For most people, probiotics during amoxicillin are well tolerated. But “most people” is doing some heavy lifting in that sentence. Reviews of probiotic risks have documented cases of opportunistic infections, adverse immune effects, and the potential for probiotic organisms to transfer antibiotic resistance genes to harmful bacteria.¹⁷ The people at real risk are those with severely weakened immune systems. A study of hematopoietic cell transplant recipients (people who received bone marrow or stem cell transplants) found that about 0.5% developed bloodstream infections from organisms found in common probiotic formulations, almost all from Lactobacillus species. The rate was highest in the first 100 days after transplant.¹⁸

If you have a central venous catheter, are receiving chemotherapy, are critically ill in an ICU, or have had an organ transplant, do not start a probiotic without your doctor’s input. For otherwise healthy adults and children taking a standard course of oral amoxicillin for a routine infection, the safety profile is reassuring across large trials.

Antibiotic Resistance and Probiotic Organisms

A less commonly discussed concern is that probiotic bacteria can carry antibiotic resistance genes, and there is a theoretical risk that these genes could transfer to harmful bacteria in your gut. A critical review of this issue noted that most people focus on the benefits of probiotics while overlooking the possibility of resistance gene exchange with pathogenic microbes.¹⁹ In practice, documented cases of this happening in a clinically meaningful way are extremely rare, and regulatory bodies in the EU now require that commercial probiotic strains be screened for transferable resistance genes before approval. But it is a reason why tossing back random high-dose probiotic cocktails “just in case” is not as risk-free as marketing materials suggest.

Amoxicillin-Clavulanate Is a Bigger Problem

If your prescription says amoxicillin-clavulanate (often sold under brand names like Augmentin), you have even more reason to consider a probiotic. The clavulanate component, a beta-lactamase inhibitor, broadens the antibiotic’s spectrum and hits the gut microbiome harder than plain amoxicillin. Diarrhea rates with amoxicillin-clavulanate are higher, and the disruption to gut flora tends to be more severe. A trial testing a Lactobacillus and Bifidobacterium combination in patients on antibiotics including amoxicillin-clavulanate found that the probiotic delayed the onset of diarrhea by four to five days compared with placebo.²⁰ Delaying onset by that long often means the diarrhea never materializes at all, since many antibiotic courses are finished within a week or two.

The B. breve PRL2020 trial mentioned earlier specifically enrolled children on either plain amoxicillin or amoxicillin-clavulanate and found its large diarrhea reduction across both groups.¹² If you are on the clavulanate combination, a probiotic is arguably more worthwhile than with amoxicillin alone, simply because the baseline diarrhea risk is higher and there is more room for a probiotic to help.

Choosing a Probiotic During Amoxicillin

Not every product on the shelf is equally suited for use alongside amoxicillin. A few practical points worth considering:

• Yeast-based options: Saccharomyces boulardii has the broadest evidence base for antibiotic-associated diarrhea prevention and is inherently resistant to amoxicillin. It is available as a standalone supplement in most pharmacies.
• Bacterial strains with resistance: Some strains, like Bifidobacterium breve PRL2020 and Bacillus clausii, have been selected or naturally possess resistance to penicillin-class antibiotics. These are less widely available but worth looking for.
• Standard Lactobacillus products: These are the most common probiotics sold, and while they are susceptible to amoxicillin, clinical trials have still shown benefits when they are taken alongside antibiotics. Staggering the doses by a couple of hours may help.
• Multi-strain formulations: Several of the positive trials used combinations of strains rather than single organisms. Diversity in the probiotic product may compensate for the fact that some strains will be killed by the antibiotic while others survive.

Probiotic-enriched yogurt and kefir are reasonable food-based alternatives, though the organism counts per serving are lower than in supplement form. The pediatric yogurt trial that showed strong results used a product with verified live cultures of specific strains at therapeutic levels, which is not the same as grabbing any yogurt labeled “contains live cultures” off the shelf.