I know that cost is a concern for you, but for what it's worth, my extensive probiotic research turned up VSL#3 as possibly the most active and effective probiotic on the market. I'm in no way affiliated with the company, but their probiotic is cited in several scientific studies. The recommended dosage under a Physician's supervision is 1/2 to 8 sachets per day, and one sachet is about $3 US. they also have a 1/2 strength VSL#3 Junior probiotic. You can get VSL#3 at pharmacies listed on their web site by entering your zip code if you are in the US, but if you order it online, they always ship it using 2 day service and it arrives refrigerated in a styrofoam cooler with ice packs. If you are not in the US, here's some international information.