Bacillus clausii

Clinically proven spore-forming probiotic bacteria that supports digestive health, prevents antibiotic-associated diarrhea, and enhances immune function with exceptional survival characteristics

Scientific nameBacillus clausii FormulaSpore-forming bacterial culture Molecular weightN/A - Living spore-forming organism g/mol CASN/A - Probiotic strain

95 absorption score

10 safety / 10

35 USD per month

6 documented interactions

Check it against something

Evidence level B

Bacillus clausii with:

78 out of 100

Works better together Compatible. Timing differs, so follow each supplement's own window.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Prevention of antibiotic-associated diarrhea

Clinically proven to prevent diarrhea during and after antibiotic treatment

Maintains gut microbiome balance and competes with harmful bacteria Evidence A-grade 1-2 weeks during antibiotic treatment

Enhanced immune system function

Strengthens immune response and reduces infection susceptibility

Stimulates immune cell activity and antibody production Evidence A-grade 4-8 weeks of consistent use

Improved digestive health and gut barrier

Strengthens intestinal barrier and reduces digestive inflammation

Produces beneficial metabolites and reinforces gut lining Evidence A-grade 2-6 weeks of regular supplementation

Exceptional antibiotic resistance

Survives most antibiotic treatments maintaining probiotic benefits

Spore formation provides natural antibiotic resistance Evidence A-grade Immediate protection during antibiotic use

Reduced respiratory tract infections

May decrease frequency and severity of respiratory infections

Enhances mucosal immunity and systemic immune response Evidence B-grade 6-12 weeks of consistent use

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Probiotics for Autoimmune Disease Support Gut health & immune modulation 10-100 billion CFU daily B 60% Magnesium Glycinate Superior absorption sleep & muscle support 200-600 mg A 90% Vitamin D3 Bone health & immune support 1000-2000 IU A 85% Magnesium Citrate Balanced absorption & digestive support 300-600 mg A 35% Chloride Electrolyte & digestive support 2300mg A 95% Bone Broth Collagen Gut healing & collagen support 20-40g powder B 85%

Every pair we checked

12 combinations scored by the engine

Bacillus clausii + Caffeine No documented interaction either way No known interaction 70

Bacillus clausii + Creatine Monohydrate No documented interaction either way No known interaction 70

Bacillus clausii + Calcium Carbonate No documented interaction either way No known interaction 70

Bacillus clausii + Whey Protein No documented interaction either way No known interaction 70

Bacillus clausii + Lactase No documented interaction either way No known interaction 70

Bacillus clausii + Bovine Collagen No documented interaction either way No known interaction 70

Bacillus clausii + DHA No documented interaction either way No known interaction 70

Bacillus clausii + Turmeric No documented interaction either way No known interaction 70

Bacillus clausii + Fish Oil (EPA/DHA) No documented interaction either way No known interaction 70

Bacillus clausii + Vitamin D3 Enhanced immune function and antioxidant protection Works better together 78

Bacillus clausii + Zinc Gluconate Synergistic immune enhancement and gut barrier support Works better together 78

Bacillus clausii + Prebiotic Fiber Complex Improved probiotic survival and beneficial metabolite production Works better together 82

Dosage

With meals or during antibiotics

Daily2-4 billion CFU

Antibiotic protection2-4 billion CFU daily during and after treatment

Immune support2-4 billion CFU daily

Digestive maintenance1-2 billion CFU daily with meals

Respiratory health2-4 billion CFU daily during high-risk periods

When to expect it

First Effects1-2 weeks for digestive protection and immune changes

Peak Benefits4-12 weeks for maximum digestive and immune benefits

Deficiency DevelopmentBeneficial bacteria depleted by antibiotics, infections, stress

Toxicity OnsetNo known toxicity - extremely safe probiotic

How to measure it

$200-400

MarkerImmune markers, inflammatory markers, stool microbiome analysis

OptimalBalanced immune function, healthy gut microbiome

Deficient belowCompromised immune markers, poor gut microbiome diversity

FrequencyMonitor during antibiotic treatment or immune health optimization

Works better with

3 documented

Vitamin C

Enhanced immune function and antioxidant protection

Both support immune system through complementary pathways · level B

Zinc

Synergistic immune enhancement and gut barrier support

Both support immune function and intestinal health · level B

Prebiotic Fiber

Improved probiotic survival and beneficial metabolite production

Prebiotics provide nutrients for beneficial bacteria growth · level A

What not to take with Bacillus clausii

3 documented

Extreme Heat Processing

Excessive heat may damage spores despite high tolerance

Very high temperatures can destroy spore viability · low significance

Artificial Preservatives

Some preservatives may reduce spore viability over time

Antimicrobial preservatives can affect beneficial bacteria · low significance

Chronic Stress

Long-term stress may impair probiotic effectiveness

Stress hormones affect gut microbiome and immune function · moderate significance

Medication interactions

Discuss these with a pharmacist before combining

antibiotics Beneficial

B. clausii spores survive most antibiotics

What to do: Can be taken during antibiotic treatment

immunosuppressive-medications Minor

Theoretical infection risk in severely immunosuppressed patients

What to do: Use caution in severe immunosuppression

Available forms

bioavailability compared

Bacillus clausii (Multiple antibiotic-resistant strains) 95

Bacillus clausii (Multiple antibiotic-resistant strains): Antibiotic resistance, Clinical validation, Immune support, Excellent survival

Food sources

before you supplement

Soil-based organisms (environmental) Natural environmental presence · 50

Fermented foods (limited natural sources) Variable, typically very low levels · 60

Functional foods with added B. clausii 10^6-10^8 CFU per serving · 85

B. clausii probiotic supplements 1-10 billion CFU per serving · 95

Too little

deficiency signs

Gut microbiome imbalance symptoms:
Antibiotic-associated diarrhea and digestive disruption
Frequent infections and compromised immunity
Poor digestive health and gut barrier dysfunction
Increased susceptibility to respiratory infections
Reduced resistance to gastrointestinal pathogens
Slow recovery from antibiotic treatments

Too much

toxicity signs

Extremely safe with minimal adverse effects:
Temporary digestive adjustment during initial supplementation
Very rare bacterial overgrowth in severely immunocompromised
No documented serious adverse effects in healthy individuals
Safe for daily long-term use

Who benefits most

antibiotic-users

Clinically proven to prevent antibiotic-associated diarrhea

2-4 billion CFU daily during and after antibiotic treatment

immune-system-support

Strengthens immune function and reduces infection susceptibility

2-4 billion CFU daily

digestive-health-maintenance

Supports overall gut health and digestive function

1-2 billion CFU daily with meals

respiratory-health-seekers

May reduce frequency of respiratory infections

2-4 billion CFU daily during high-risk periods

gut-barrier-dysfunction

Strengthens intestinal barrier and reduces leaky gut syndrome

2-4 billion CFU daily

Where to buy it

compare forms first

Look for Bacillus clausii at 2-4 billion CFU per serving. The form that matters here is Bacillus clausii (Multiple antibiotic-resistant strains).

Find on Amazon

Affiliate link — we may earn a commission at no cost to you.

What else affects it

Beyond other supplements

Extreme heat processing

Excessive heat may damage spores despite high tolerance

Very high temperatures can destroy spore viability

Artificial preservatives

Some preservatives may reduce spore viability over time

Antimicrobial preservatives can affect beneficial bacteria

Chronic stress

Long-term stress may impair probiotic effectiveness

Stress hormones affect gut microbiome and immune function

How it works

Forms highly resistant spores surviving antibiotic treatments
Produces antimicrobial compounds inhibiting pathogenic bacteria
Stimulates secretory IgA production for mucosal immunity
Modulates immune cell activity and cytokine production
Competes with pathogenic bacteria for nutrients and binding sites
Strengthens gut barrier function through beneficial metabolite production

Key findings

what the evidence supports

Clinically proven effective for preventing antibiotic-associated diarrhea
Strong evidence for immune system enhancement
Exceptional antibiotic resistance and survival characteristics
Excellent safety profile with minimal adverse effects

Sources: NIH Examine.com · data reviewed 2026-08-01

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Bacillus clausii?

Documented effects: Prevention of antibiotic-associated diarrhea; Enhanced immune system function; Improved digestive health and gut barrier; Exceptional antibiotic resistance. Clinically proven to prevent diarrhea during and after antibiotic treatment

How much Bacillus clausii should you take per day?

The common daily range is 2-4 billion CFU. By goal — antibiotic protection: 2-4 billion CFU daily during and after treatment; immune support: 2-4 billion CFU daily; digestive maintenance: 1-2 billion CFU daily with meals; respiratory health: 2-4 billion CFU daily during high-risk periods.

When is the best time to take Bacillus clausii?

With meals or during antibiotics. First effects are typically reported within 1-2 weeks for digestive protection and immune changes.

What are the side effects of Bacillus clausii?

At excessive doses: Extremely safe with minimal adverse effects:, Temporary digestive adjustment during initial supplementation, Very rare bacterial overgrowth in severely immunocompromised, No documented serious adverse effects in healthy individuals, Safe for daily long-term use. Safety rating at normal doses is 10 out of 10.

What should you not take with Bacillus clausii?

Separate it from Extreme Heat Processing, Artificial Preservatives, Chronic Stress by two to four hours. Excessive heat may damage spores despite high tolerance

Does Bacillus clausii interact with medications?

Documented interactions with antibiotics, immunosuppressive-medications. Discuss these with a pharmacist before combining.

How do you know if you need Bacillus clausii?

The marker is Immune markers, inflammatory markers, stool microbiome analysis, optimal range Balanced immune function, healthy gut microbiome. Common deficiency signs: Gut microbiome imbalance symptoms:, Antibiotic-associated diarrhea and digestive disruption, Frequent infections and compromised immunity, Poor digestive health and gut barrier dysfunction.

Taken for

59 Immunity

Vitamin D3 · Vitamin C (Ascorbic Acid) · Comprehensive Immune Support Complex

74 Digestion

Lactase · Lactobacillus acidophilus · Protease