CFU Vs Milligrams: Why A Probiotic Label Can Tell You Less Than You Think
A milligram figure on a probiotic label describes weight. It does not describe how many live, viable bacteria are actually in your capsule.
Colony-forming units (CFU) is the number that measures potency directly — and it is the figure most commonly missing from otherwise transparent-looking labels.
What CFU actually measures
Colony-forming units (CFU) is a count of viable, live bacterial cells capable of reproducing and colonising the gut. It is the standard measure of probiotic potency used in clinical research, typically expressed in the billions per serving for an effective dose.
Why milligram weight is a weaker substitute
A milligram of freeze-dried probiotic powder can contain dramatically different numbers of live organisms depending on the strain, the freeze-drying process, storage conditions and the age of the product by the time it reaches you. Two products stating identical milligram amounts of the same strain can have meaningfully different CFU counts — and therefore meaningfully different potency.
This means a label that states ‘36mg probiotic blend’ without a CFU figure has told you something about weight, but very little about how many live bacteria are actually going to reach your gut.
Why some brands disclose milligrams but not CFU
We cannot speak to intent for any specific brand, but milligram weight is simpler to state consistently across batches, while CFU counts can decline over a product's shelf life unless the manufacturer specifically formulates and tests for a guaranteed CFU count through the expiration date — a more rigorous (and more expensive) manufacturing standard.
What to look for on a well-disclosed probiotic label
What to do if the CFU count is missing
Email the manufacturer directly and ask. A brand confident in its formulation should be able to provide a CFU count and clarify whether it is guaranteed through shelf life. If you cannot get a clear answer, factor that into how much weight you put on the probiotic side of the formula specifically — separately from the disclosed prebiotic fibre amounts, which are a different, simpler measurement that milligrams describe accurately.
Applying this to SodaTide
SodaTide states its probiotic blend weighs 36mg total across three strains, without a CFU count or strain-by-strain breakdown. The two prebiotic fibres (211mg inulin, 100mg resistant starch) are disclosed clearly and milligram weight is the correct, meaningful measurement for those — it is only the probiotic side where the missing CFU figure is a real limitation.
