he individual number of viable probiotics is known as CFU (Colony Forming Unit). This is actually a microbiology measure used to describe and quantify bacteria of all types (not just probiotics).
CFU is therefore an important concept in quantification of probiotics. As a measure of the amount of probiotics, it is also used to track and qualify the viability of good bacteria through production, storage, transportation and final delivery to your gut.
All (most) Probiotics will state on their label the amount of probiotic species/strains they contain per serving in CFU. This should be the amount expected at the time of purchase. However, this is not always the case.
Probiotic viability is a major issue. The ability to keep good bacteria viable from production and manufacturing, storage in warehouse & pharmacy, transportation and finally in your hands is a massive challenge.
WHO and FAO have provided guidelines of the amount of viable probiotics that should be contained in a product before claims of health benefits can be made. This number is currently a concentration of 106 to 107 CFU (Colony Forming Units)