How long it takes for a probiotic to work depends on the strain, the potency, and what you are taking them for. For antibiotic-associated diarrhea, it’s recommended that you take probiotics within the first 48 hours of your first dose of antibiotics. If you are taking the recommended single strain of Saccharomyces boulardii found in Renew Life Ultimate Flora Probiotic for Adults, you should not experience diarrhea at all; that’s your sign that they are working! For pouchitis, we don’t know when probiotics start to work. However, the appropriate probiotics can not only prevent pouchitis but can also lead to quick healing of acute pouchitis compared to those who do not use probiotic supplementation.