Exact ingredient or strain: For probiotics, strain identity matters. Two products may both contain Bifidobacterium, but that does not mean they have the same clinical evidence.
Appropriate amount: More CFUs are not automatically better. The useful amount depends on the exact organism, formulation, and intended use — the same principle applies to fiber, digestive enzymes, and Berberine.
Stability: Live probiotic organisms must remain viable through the product's intended shelf life. Check whether refrigeration is required and whether the company states potency at manufacture or through expiration.
Third-party testing: Can help verify ingredient identity, potency, microbial quality, heavy metals, and other contaminants where relevant.
Certificate of Analysis: Do not treat the words “COA available” as enough by themselves. Check whether the report identifies the product or lot, verifies potency, confirms identity, reports contaminant testing, and shows whether the sample met specification.