What happens when you take probiotics with immunosuppressants?
Probiotics are live microorganisms, most often Lactobacillus, Bifidobacterium, or the yeast Saccharomyces boulardii, taken to support gut and immune health. Immunosuppressants such as tacrolimus, cyclosporine, sirolimus, everolimus, mycophenolate, azathioprine, and chronic corticosteroids deliberately blunt the immune response to protect a transplanted organ or control autoimmune disease. The combination creates a problem because the same suppression that protects the transplant also removes the body's normal containment of gut microbes.
- The immune system is deliberately weakened. Immunosuppressant drugs reduce the body's ability to police bacteria, including the harmless organisms that normally stay inside the gut.
- Probiotic organisms can cross the gut wall. In a suppressed host, live Lactobacillus, Bifidobacterium, or Saccharomyces can translocate across the intestinal barrier rather than staying contained, a process called bacterial translocation.
- They enter the bloodstream as live organisms. Once across the barrier, the supplement strains circulate as potential pathogens instead of gut residents.
- Invasive infection can follow. Translocated organisms have been linked to bacteremia, endocarditis, liver abscess, fungemia, and sepsis in transplant and oncology patients. The event is uncommon, but when it happens it is serious.
Why is this important?
Probiotics are sold as foods or dietary supplements, so they do not carry prescription-style warning labels. Many people on immunosuppressants assume that anything sold over the counter, especially something described as natural, is universally safe. For someone whose immune system is suppressed, a rare event becomes a serious one.
These infections can also be hard to treat. Several probiotic Lactobacillus strains are intrinsically resistant to vancomycin, a first-line antibiotic for gram-positive bacteremia, and lactobacilli or bifidobacteria are not always recognized as true pathogens on blood culture. That can delay diagnosis and effective treatment until a patient is already very unwell. Handling probiotic capsules near a central venous catheter has also been linked to infection of the line itself.
A matched case-control study at OHSU found that probiotic use was markedly more common among patients who developed invasive infections than among controls, and a renal-transplant case report describes Lactobacillus bacteremia in an immunocompromised patient on transplant immunosuppression. The direction and the mechanism are well supported by the evidence.
What should you do?
Before any change: If you take an immunosuppressant, do not start a probiotic supplement, drink, shot, or powder without first speaking to your transplant team, rheumatologist, or oncologist. This includes products marketed for general gut health, antibiotic-associated diarrhea, or immune support, and it includes Saccharomyces boulardii, which is a yeast that can cause fungemia. Bring any product you are considering, fermented foods included, to that conversation.
Every day, if a probiotic has been specifically cleared or prescribed: Take it exactly as your clinician directed. Wash your hands after handling capsules, and avoid opening or handling them near a central venous catheter. If you care for an immunocompromised person at home, wash your hands thoroughly after taking your own probiotic before contact with them.
After starting, or if anything changes: Report any new fever, chills, abdominal pain, or other signs of infection promptly rather than waiting. Plain yogurt and traditional cheeses carry lower live counts and are usually permitted, but heavily fermented products such as kombucha, raw kefir, and unpasteurized sauerkraut should also be reviewed with the prescribing team. Many transplant and oncology wards now restrict probiotic products for these reasons.
Which specific products are affected?
The caution applies broadly to single- and multi-strain probiotic supplements containing Lactobacillus rhamnosus GG, Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium species, Streptococcus thermophilus, and Saccharomyces boulardii. Probiotic capsules, powders, drinks, and shots sold for gut or immune support all fall under this caution when used alongside immunosuppressants.
Immunosuppressants that trigger this caution include tacrolimus, cyclosporine, sirolimus, everolimus, mycophenolate, azathioprine, methotrexate at immunosuppressive doses, chronic systemic corticosteroids such as prednisone, and immune-suppressing biologics such as rituximab, infliximab, and adalimumab. Patients receiving chemotherapy, particularly during neutropenia, belong in the same category.
The science behind it
A matched case-control study from OHSU (Tom et al., Infection Control & Hospital Epidemiology, 2021) found that probiotic use was substantially more common among patients with invasive infections than among matched controls, supporting a real association rather than coincidence. A renal-transplant case report (PMC7058391) documents Lactobacillus rhamnosus bacteremia in an immunocompromised patient on transplant immunosuppression. A separate case cluster used whole-genome sequencing to show that Lactobacillus bloodstream infections in pediatric hematopoietic-cell-transplant patients were genetically related to the probiotic products they had taken (PMID 35225182), which is among the strongest evidence that the supplement was the source. The evidence is built from case reports, a case cluster, and one case-control study, so it establishes a credible, well-documented hazard rather than a precise risk figure.
Frequently Asked Questions
Are probiotics dangerous for everyone?
No. In people with a healthy immune system, probiotic organisms are normally contained in the gut and pose very little risk. The concern here is specific to people whose immune systems are suppressed by medication or illness.
What about yogurt and fermented foods?
Plain yogurt and traditional cheeses carry far lower live counts than concentrated supplements and are usually permitted, but heavily fermented products such as kombucha, raw kefir, and unpasteurized sauerkraut should be reviewed with your prescribing team.
Is Saccharomyces boulardii safer because it is a yeast, not a bacterium?
No. As a live yeast it can cause fungemia in immunocompromised hosts, so it carries the same caution as bacterial probiotics in this setting.
Why are these infections hard to treat?
Several probiotic Lactobacillus strains are naturally resistant to vancomycin, a first-line antibiotic for this kind of bloodstream infection, and the organisms are not always recognized as true pathogens, which can delay diagnosis.
My doctor prescribed a probiotic. Should I stop it?
Do not stop a prescribed treatment on your own. Take it as directed, and contact the clinician who prescribed it if you have concerns or develop any signs of infection such as fever or chills.
Can I take a probiotic if I time it apart from my immunosuppressant?
Spacing them out does not remove the risk, because the concern is the live organism in a suppressed body, not a timing-based absorption clash. Clear any probiotic with your care team first.
Key takeaways
- For people on immunosuppressant therapy, live probiotic organisms can occasionally cross the gut wall and cause bloodstream infection.
- The risk is uncommon but well documented and the consequences are serious, including bacteremia and sepsis.
- Some probiotic strains resist first-line antibiotics, which can make these infections harder to treat.
- Clear any probiotic supplement, drink, shot, or heavily fermented food with your transplant, rheumatology, or oncology team before using it.
- Report new fever, chills, or abdominal pain promptly if you are immunosuppressed.