Probiotics Dosage Calculator
Live microorganisms that confer measurable health benefits when consumed in adequate amounts. Evidence spans IBS relief, antibiotic-associated diarrhoea prevention, immune modulation, and mood.
What is Probiotics?
Probiotics are defined by the WHO as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host." The most clinically studied genera are Lactobacillus, Bifidobacterium, and Saccharomyces boulardii (a probiotic yeast). Benefits are strain-specific — a meta-analysis may support "Lactobacillus" broadly, but this does not mean all lactobacillus strains produce the same effect. Well-evidenced applications include: antibiotic-associated diarrhoea prevention (L. rhamnosus GG, S. boulardii — reduce risk by ~60%); IBS symptom improvement (L. plantarum 299v, VSL#3); reduction in upper respiratory infection duration and frequency; and the gut-brain axis — Lactobacillus rhamnosus JB-1 reduced anxiety behaviour in mouse models, with emerging human data. Dose is measured in CFU (colony-forming units): typical therapeutic ranges are 5–50 billion CFU/day.
How to Take Probiotics
**General gut health/maintenance:** 5–10 billion CFU/day of a multi-strain product containing Lactobacillus and Bifidobacterium species. **IBS:** 10–50 billion CFU/day of a strain-specific product (L. plantarum 299v or VSL#3) for at least 4–8 weeks. **During antibiotic course:** 20–50 billion CFU/day of L. rhamnosus GG or S. boulardii, taken at least 2 hours after each antibiotic dose, continued for 1–2 weeks after the antibiotic course ends. Refrigerated probiotics maintain viability better than shelf-stable; check expiry date and CFU at end-of-shelf-life (not at manufacture).
Timing Recommendations
Take probiotics 20–30 minutes before a meal or with food — gastric acid pH is lower during fasting, reducing bacterial survival. Never take simultaneously with a hot beverage. During antibiotic courses, separate probiotic dosing from antibiotic dosing by a minimum of 2 hours to prevent the antibiotic from killing the probiotic organisms before they reach the colon.
Potential Side Effects & Safety
Bloating and gas are common in the first 1–2 weeks as the gut microbiome adjusts — typically transient. Start with lower doses and titrate up. Rare serious adverse events (septicaemia, fungaemia) have been reported only in severely immunocompromised patients (post-organ transplant, ICU with central lines) — standard contraindication for this population.
Who should avoid Probiotics?
Severely immunocompromised individuals (organ transplant recipients on immunosuppressants, haematological malignancy patients, ICU patients with central venous catheters) should avoid live probiotic organisms due to rare but documented risk of translocation sepsis. Short-bowel syndrome: use only under gastroenterologist supervision.
Best Stacks with Probiotics
Probiotics + prebiotics (inulin, FOS, psyllium husk) = synbiotics — prebiotics serve as fermentable fibre substrate for probiotic bacteria. Probiotics + magnesium glycinate for IBS-constipation variant. Probiotics + L-glutamine (5 g/day) for intestinal barrier repair in leaky gut syndrome.
Scientific References
All dosage recommendations are grounded in peer-reviewed research.
- 1
- 2Efficacy of probiotics in irritable bowel syndrome: a systematic review of randomized controlled trials
Alimentary Pharmacology & Therapeutics · 2019
Probiotics Dosage Calculator
Fixed dosage — independent of body weight
Your recommended daily dosage
Formula: 5–10 billion CFU/day (maintenance) | 20–50 billion CFU/day (antibiotic course, IBS therapy)
Safety notes
- During antibiotic use, take probiotics at least 2 hours after your antibiotic dose.
- Severely immunocompromised patients (post-transplant, ICU): do NOT take live probiotics without physician approval.
- Initial bloating and gas are normal for the first 1–2 weeks — start at the lower dose and increase gradually.
- Check that CFU count is guaranteed at end-of-shelf-life (not at time of manufacture) — refrigeration preserves viability.
- Strain specificity matters — not all probiotics treat all conditions. Match the strain to the indication.
This calculator provides general guidance only. Always consult a qualified healthcare professional before starting any supplement.