What should you actually look for on a probiotic label? Most of what gets highlighted on the front panel, including strain diversity and CFU counts in the billions, tells you very little about whether the product will perform as advertised.
CFU at Manufacture vs. CFU at Expiry
CFU stands for colony-forming units, the standard measure of live bacteria in a supplement dose. The large number on the front of most probiotic bottles reflects the count at the time of manufacture, before the product has sat in a warehouse or on a store shelf.
What matters is the count at the time you take it. Look for language like "CFU guaranteed through expiry" or "viable at best by date." If the label only states the count at manufacture, you have no guarantee of what remains by the time the bottle reaches you.
Full Strain Names and Strain Codes
Probiotic strains are identified by a three-part name: genus, species, and strain code. A complete designation looks like Lactobacillus rhamnosus GG or Bifidobacterium longum BB536. The strain code is what links a product to specific published research on that particular microorganism.
Labels that list only genus and species, such as "Lactobacillus acidophilus" without a strain code, give you no way to identify what clinical data, if any, applies to that strain. It is not evidence the product is ineffective, but it is evidence you cannot verify the claimed identity.
Proprietary Blends
Some products list all their strains under a single proprietary blend total, such as "Probiotic Blend 10 billion CFU." This hides the individual strain amounts. You cannot determine how much of any one strain is present, or whether any individual strain meets a meaningful dose level.
Look for products that list each strain separately with its individual CFU count.
Prebiotics
Many probiotics include prebiotic fibers intended to feed the bacteria in the supplement. A product combining both is called a synbiotic.
Prebiotics are not required for a probiotic to function. If you are sensitive to fermentable fibers such as inulin or FOS, check the ingredient list before purchasing, since some people experience gas or bloating with prebiotic additions.
Storage and Packaging
Live bacteria are sensitive to heat and moisture. Probiotics that require refrigeration can lose significant viability if they ship or are stored at room temperature.
Check the storage instructions before you buy. If the label says refrigerate, confirm that the retailer ships with a cold pack, and inspect the seal when the package arrives.
Some strains are shelf-stable due to protective encapsulation or freeze-drying technology. Shelf-stable does not mean inferior or superior, just that the product does not require refrigeration if stored according to its own label instructions.
Third-Party Testing
Dietary supplements, including probiotics, are not pre-approved by the FDA before going to market. The CFU count and strain identity on the label depend on the manufacturer's own testing.
Third-party certification programs like NSF International, USP, and Informed Sport test products independently for label accuracy and contaminants. A current certificate of analysis, often available on the brand's website, is a stronger signal than a seal alone.
The Short Version
Before choosing a probiotic, check for: CFU count guaranteed at expiry, full strain names with strain codes, individually listed strains with separate counts, and current third-party testing. Storage requirements and prebiotic ingredients are secondary considerations once you have confirmed those four.
For specific options that meet these label standards, see the supplements recommendations page.