How long probiotics take to work depends on the strain of the probiotic, as well as the condition being treated. For instance, the supplementation of Bacillus coagulans showed an improvement in IBS symptoms after 8 weeks¹, while a combination of multiple probiotic species resulted in improved IBS symptoms after 4 weeks². On the other hand, the use of Saccharomyces boulardii in treating diarrhea showed effects within 5 days of sustained use³. For constipation, the use of L. casei showed improvement in symptoms 2-4 weeks into the treatment⁴.