Can Probiotics Cause Low White Blood Cell Count? Understanding the Risk

January 9, 2026 •

4 min read

While typically associated with positive health benefits, a 2017 study found that patients with acute myeloid leukemia undergoing intensive treatment who received probiotics experienced a higher incidence of documented infections, including bloodstream infections. The potential for probiotics to cause low white blood cell counts, or neutropenia, is a significant concern, particularly for immunocompromised individuals.

Quick Summary

This article explores the relationship between probiotic use and white blood cell count, clarifying that while probiotics are not a direct cause of low WBCs, they can pose a serious risk of infection for immunocompromised individuals with existing low counts. It details the mechanisms by which probiotics modulate the immune system, outlines the dangers for vulnerable patients, and provides guidance for safe usage.

Key Points

Probiotics do not cause low WBC count: For healthy individuals, probiotic supplements do not directly cause a decrease in white blood cell counts; in some cases, they may even support immune cell function.
Risk is for immunocompromised individuals: The primary risk is for people with already compromised immune systems, such as those undergoing chemotherapy, who may already have a low white blood cell count (neutropenia).
Increased infection risk: For immunocompromised patients, the live microorganisms in probiotics can cause serious, life-threatening infections, like sepsis, because their body cannot fight off the bacteria if it enters the bloodstream.
Strain and quality vary: Probiotics are not FDA-regulated as drugs, so the quality and contents of supplements can vary, posing an additional theoretical risk for vulnerable populations.
Avoid without medical supervision: Immunocompromised individuals should avoid probiotic supplements unless they have consulted with a healthcare provider and are under careful medical supervision.
Immune system modulation: Probiotics interact with the gut-associated lymphoid tissue, where most immune cells are, to regulate immune responses. This beneficial modulation in healthy people becomes a risk in the immunocompromised.

Do Probiotics Directly Cause a Low White Blood Cell Count?

For the vast majority of healthy people, probiotics do not cause a low white blood cell (WBC) count. In fact, most of the scientific evidence points to probiotics either having no significant effect on WBC counts or, in some cases, even helping to increase immune cell activity. Low white blood cell counts, also known as leukopenia or neutropenia (when specifically referencing neutrophils, a type of WBC), are typically caused by other factors, such as:

Intensive medical treatments: Chemotherapy and radiotherapy are well-known causes of low WBC counts.
Autoimmune disorders: Conditions where the immune system attacks its own cells can lead to lower WBC levels.
Bone marrow problems: Diseases or conditions that impair the bone marrow's ability to produce blood cells.
Viral infections: Some viral infections can temporarily lower WBC counts.
Certain medications: Some drugs can have the side effect of decreasing WBC production.

While probiotics themselves are not the cause, the risk arises when immunocompromised individuals—who may already have a low WBC count due to their underlying condition or treatment—introduce live microorganisms into their system.

The Risks for Immunocompromised Individuals with Low WBCs

For a person with a healthy immune system, ingesting live microorganisms from probiotics is typically a beneficial or neutral process, as the body's robust defenses can easily handle and regulate the new bacteria. However, in a severely immunocompromised state, particularly for patients with prolonged neutropenia, this dynamic changes dramatically. The live microbes, which are normally benign, can potentially overwhelm the compromised immune system and lead to serious, life-threatening infections, including sepsis. This is because the body lacks the white blood cells necessary to contain the probiotic bacteria if they cross the intestinal barrier and enter the bloodstream.

Studies have documented this danger:

One retrospective analysis of leukemia and hematopoietic stem-cell transplant patients found that those taking probiotics had a significantly higher incidence of documented bloodstream infections compared to those who did not.
Case reports have also detailed instances of sepsis linked to probiotic use in critically ill, postoperative, and immunocompromised patients.
Product manufacturers often include warnings for immunosuppressed patients, recommending they avoid live cultures.

The Role of Probiotics in Immune Modulation

Probiotics interact with the immune system in a complex way, primarily through the gut-associated lymphoid tissue (GALT), where a large portion of the body's immune cells reside. They can influence both innate and adaptive immunity through various mechanisms:

Strengthening the gut barrier: By promoting the integrity of the intestinal lining, probiotics prevent harmful pathogens from entering the bloodstream.
Modulating immune cells: Probiotics can influence the activity of dendritic cells, T cells, and B cells, which can either promote an immune response or induce immune tolerance.
Producing antimicrobial compounds: Certain strains can produce substances that inhibit the growth of harmful bacteria.

In healthy individuals, this modulation is often beneficial, strengthening the body's overall defense. However, in the absence of a sufficient WBC count, this interaction can become a liability rather than an asset.

Probiotics vs. Low White Blood Cell Counts: A Comparison

To better understand the distinct nature of probiotics and low white blood cell conditions, consider the following comparison:


Feature	Probiotic Use (Healthy Individual)	Low White Blood Cell Count (Immunocompromised Patient)
Effect on WBCs	Typically neutral or slightly stimulatory, improving immune function.	The underlying condition or treatment has already reduced the number of WBCs.
Immune System State	Robust and capable of managing new microbial input without issue.	Severely weakened, with inadequate defenses to combat potential infections.
Primary Risk	Generally low. Some may experience mild digestive side effects.	Serious systemic infection (e.g., sepsis) if live microbes cross the gut barrier.
Action	Modulate gut-based immune responses for overall health benefits.	The lack of immune cells makes the patient vulnerable to any source of infection.
Recommendation	Generally safe and beneficial.	Avoided entirely unless directed by a physician.

This table highlights why the same substance can have drastically different outcomes depending on the patient's immune status. The danger for immunocompromised individuals is not that probiotics cause the low count, but that the low count makes them exceptionally vulnerable to the inherent nature of a live microbial supplement.

The Verdict: Can Probiotics Cause a Low White Blood Cell Count?

Based on current research, probiotics do not cause a low white blood cell count in a healthy person. The fear surrounding this topic stems from a critical misunderstanding of the risk profile. For healthy individuals, probiotics support the immune system and gut health. The real danger lies with severely immunocompromised individuals, particularly those with existing neutropenia, who are at a significantly increased risk of developing serious, potentially fatal infections from live bacteria in probiotics. It is imperative for individuals with weakened immune systems due to conditions like cancer, HIV, or organ transplants to avoid probiotic supplements unless explicitly advised and monitored by their healthcare provider. The conversation around probiotics and low WBCs is not about causation but about risk management in vulnerable populations.

Conclusion

While probiotics are a popular and generally safe supplement for supporting gut health and immunity in healthy people, they are not without risks, especially for those who are immunocompromised. The scientific consensus indicates that probiotics do not cause a low white blood cell count. Instead, patients who already have low WBC counts due to serious medical conditions or treatments face a heightened risk of infection from the live bacteria in these supplements. Before taking any new supplement, particularly if you have an underlying medical condition, always consult with a healthcare professional to ensure it is safe and appropriate for your specific health needs.

Important Considerations

Always inform your doctor of any supplements you are taking or considering, especially if you are undergoing intensive medical treatment.
Read labels carefully. Some food products containing probiotics, like yogurt with live cultures, may also be risky for immunocompromised individuals, as advised by some dietary guidelines.
For those with low white blood cell counts, a doctor may recommend pasteurized products instead of those containing live cultures.

Frequently Asked Questions

No, probiotics are not safe for everyone. While generally safe and beneficial for healthy individuals, they carry a significant risk of causing serious infection, including sepsis, for those with weakened immune systems, such as people on immunosuppressant drugs, chemotherapy patients, or those with critical illnesses.

Patients undergoing chemotherapy, especially those at risk for prolonged neutropenia, are often advised against taking probiotics. A retrospective analysis found a higher incidence of bloodstream infections in these patients when they used probiotics, suggesting no benefit and potential harm.

In healthy people, probiotics typically do not significantly alter white blood cell counts. Instead, they interact with the gut's immune system to modulate and often enhance immune function, rather than lowering cell numbers.

Neutropenia is a condition characterized by an abnormally low number of neutrophils, a key type of white blood cell. It is not caused by probiotics, but a person with neutropenia is at high risk of infection from the live bacteria in probiotics because their body lacks the ability to fight them off.

The risk arises because the live bacteria in probiotics could translocate from the gut into the bloodstream. A healthy immune system can prevent this, but a compromised one cannot, which can lead to systemic infections like sepsis.

Yes, if you have a low white blood cell count or are immunocompromised, you should avoid live cultures, including those found in many yogurts. Some dietary guidelines for neutropenic patients recommend choosing pasteurized dairy products instead.

For healthy individuals, mild side effects like temporary gas, bloating, or digestive discomfort can occur as the gut adjusts. These symptoms usually resolve within a few days.

The gut is home to about 70-80% of the body's immune cells. The gut microbiome directly communicates with these cells, and a healthy balance of microbes is crucial for educating the immune system and maintaining overall immune homeostasis.