Probiotic labels: what CFU, strain names and expiry should tell you

A good probiotic label names the genus, species and strain of each organism, gives the amount in CFU (colony-forming units), and says whether that number holds through the expiration date. A big "billions" figure alone tells you very little, because health effects depend on the strain and the amount studied for that strain. If a label has none of those details, you cannot compare the product with any research.

This guide explains each label detail, what a lab study of retail products found, and how several offers we reviewed handle it. It is not medical advice.

What is a probiotic, and why does the strain matter?

The definition most often used in research, from FAO and WHO, is "live microorganisms which when administered in adequate amounts confer a health benefit on the host". Two phrases in it drive everything on a label: "live" and "adequate amounts".

The National Center for Complementary and Integrative Health (NCCIH) says different types of probiotics may have different effects. Its example: if one kind of Lactobacillus helps prevent an illness, that does not mean another Lactobacillus, or any Bifidobacterium, would do the same. It also says that in most instances we still do not know which probiotics are helpful, how much people would need to take, or who is most likely to benefit.

So a label that says only "Lactobacillus blend" is like a medicine label that says only "a pain reliever". You need the name of the actual strain.

How do you read a strain name?

A full name has three parts and often a fourth. For example, Lactobacillus rhamnosus is a genus and species, and a code such as "GG" after it identifies the specific strain. ISAPP says responsible manufacturers list the genus, species and strain. The code matters because studies are run on a specific strain, and results do not automatically carry over to other strains of the same species.

Watch for these patterns:

• Species with no strain code. Real, but you cannot match it to a trial.
• A named strain that the page then cites the wrong study for. Our ProDentim review records named strains but no amounts, and a key study that tested a different strain.
• "Proprietary blend" of strains. One combined weight and CFU figure for many organisms hides how much of each you get.

What does CFU mean, and is more always better?

CFU stands for colony-forming units, a count of live organisms that can multiply. One billion is 1,000,000,000, so "10 billion CFU" is 10 followed by nine zeros. The number is only meaningful for the strain it describes. Different strains have been studied at very different amounts, and NCCIH says the right amount is still unknown for most uses.

The LeanBiome review gives a good example. Its label lists Lactobacillus gasseri at 25 mg, equal to 10 billion CFU, and our review notes that the trial it cites found reduced visceral fat with as little as about 100 million CFU a day of a specific strain. So 10 billion clears the studied amount, but only for that strain. The same label puts seven species into one 10 mg, 5-billion-CFU blend line, including L. fermentum, which the sales page promotes by name. The review concludes the actual dose of that organism is unknown.

Notice too that milligrams tell you almost nothing here. The 25 mg and the 10 billion CFU describe the same ingredient in two different ways. When you compare two products, compare CFU per strain, not milligrams.

Why do "CFU at manufacture" and "CFU at expiry" differ?

Probiotics have to stay alive until you consume them, so the count on the day you swallow one is what matters. ISAPP tells consumers to check the label for storage conditions and expiration date, and says responsible manufacturers list the potency you can expect through the end of the shelf life.

That last part is the test. "10 billion CFU at time of manufacture" is a weaker promise than "10 billion CFU through the expiration date". The Synaptigen review notes that its label gives 3.5 billion CFU at manufacture for a three-strain blend, and that counts fall over shelf life. The same review points out that a 2020 meta-analysis of 11 probiotic trials in 724 people found no significant effect on global cognition, a mismatch with the memory claims on the sales page.

Also check whether the product needs refrigeration. ISAPP says some supplements need it and others are stable at room temperature, and you should follow the label.

Do the products in the bottle match the label?

A peer-reviewed study in Frontiers in Microbiology tested 182 probiotic supplements (520 strains in total) sold in the United States and Canada. It found that 11 declared species could not be detected in ten products, and that undeclared species showed up in one. Viable counts were measured for 72 samples; five had counts lower than declared, including one with no viable cells. Overall, 15 of the 182 products (8 percent) were non-compliant.

The finding cuts both ways. Most products met their claims, so the category is not a scam by default. But roughly one in twelve did not, which is why a label that promises specifics is worth more than one that promises nothing. Also, if a label gives no strains or amounts, there is nothing for anyone to check the product against. We cover more label checks in our blog guides.

What if the label gives no strains or CFU?

This is the most common problem in the offers we review.

• The Gut Vita review records a "4 Live Strain Probiotics" line with no strain names and no CFU count.
• The DentaVive review lists five named strains, which is better, but no amount for any of them.

In both cases the research on probiotics cannot be compared with the product, because the studies were run on named strains at stated counts. That does not make the product unsafe. It means the page has asked you to trust the ingredient name.

Checklist: what a probiotic label should give you

1. Genus, species and strain code for every organism.
2. CFU for each strain, or at least a total with the strains named.
3. A statement of whether CFU is guaranteed through expiry, not only at manufacture.
4. An expiration date and clear storage directions (refrigerate or room temperature).
5. A named company and contact details for reporting problems.
6. A study on that strain, at that amount, for the benefit the page claims.
7. A refund window you can use if you decide it is not for you. See our review method and the gut health category for how we record these.

FAQ

How many CFU should a probiotic have?

There is no single right number. NCCIH says researchers still do not know how much people would have to take for most conditions. Look for the amount used in the study of the specific strain you are buying.

Are probiotics safe for everyone?

NCCIH says probiotics have an extensive history of apparently safe use, particularly in healthy people, but the risk of harmful effects is greater in people with severe illnesses or weakened immune systems. In 2023 the FDA warned that premature infants given probiotics are at risk of severe, potentially fatal infections. Ask a doctor first if either situation applies.

Does the FDA approve probiotic supplements?

NCCIH explains that many probiotics are sold as dietary supplements, which do not require FDA approval before they are marketed. Labels may make structure or function claims, but they are not allowed to make health claims, such as lowering the risk of a disease, without FDA consent.

How long should I try one?

ISAPP suggests trying a product for about a month and considering that it may not be the right one if you see no benefit. If symptoms are severe or persistent, see a clinician instead.