I've had C. Diff before. I was prescribed an antibiotic for an infection again and the doc was not concerned about my getting C. Diff again. I got C. Diff again. :( Well, now I know. :( I went and got tested for C. Diff, but started taking the Jarrow Saccharromyces Boulardii MOS (I had it on hand from the last time I had C. Diff) right after "donating" the sample and while I waited for results (about 24 hours). The result was that I had C. Diff like I thought, so the doc called in the script for Flagyl, but I was unable to pick it up until the next day. By then, my stomach felt better and everything was on the up swing. I called the doc and asked what he thought and he said that if things were getting better, I could wait to take the Flagyl and see if the probiotics took care of the C. Diff. In 5 days I was pretty much all better. This is really good since I have Epilepsy and the metronidazole (Flagyl) has the potential to cause me to have a breakthrough seizure. I'm very pleased with the product and will continue to purchase it for use as a daily suppliment. My doc is a regular MD allopath, btw, not a naturopath or a DO. Anyway, I'm super happy with the product and also happy I didn't have to pay a TON for the other product at the local drugstore and that I avoided another round of a potentially dangerous antibiotic