What Does CFU Mean on a Probiotic Label?
CFU means colony forming units — a count of viable organisms, usually stated in billions. The detail that matters more than the number is whether that count is guaranteed at expiry or only at time of manufacture, because viable counts decline over shelf life.
CFU stands for colony forming units. It is a count of viable micro-organisms — organisms capable of reproducing — and it is the standard way probiotic products state their content.
Why a count, not a weight
Probiotics are live organisms, so what matters is how many are alive, not what they weigh. Two products of identical weight could contain wildly different numbers of viable organisms. Counts are usually printed in billions.
The question most labels leave unanswered
Viable counts decline over shelf life. A product can state its count in two quite different ways:
- At time of manufacture — how many were present when it was made. What remains when you take it is unstated.
- At expiry, or through end of shelf life — a guarantee that the stated count is still present at the end of the dating period.
The second is a substantially stronger commitment, and the difference between the two can be large. Where a label does not specify, it is reasonable to assume the weaker one. This is arguably the single most useful thing to look for on a probiotic panel.
Higher is not automatically better
A large CFU number is one variable among several. Which strains are present, whether those strains match the research being referenced, and whether the organisms survive to where they are intended to act all matter alongside the count. A 100 billion CFU product of unnamed strains is not obviously preferable to a 10 billion CFU product of well-characterised ones — see probiotic strains explained.
Per serving, not per capsule
As everywhere on a supplement facts panel, the count refers to a serving, and the serving may be more than one capsule. Check the serving size line above the count.
Storage
Some products require refrigeration to maintain viability and say so, often in small print. Others are formulated to be shelf-stable. A refrigerated product bought online in summer has had a journey worth thinking about.
Our probiotic comparison filters by brand, strength and format so you can line up counts directly.
References
- NIH Office of Dietary Supplements — Probiotics (Health Professional Fact Sheet)
- NCCIH — Probiotics: What You Need To Know