How to Choose the Right Probiotic and Avoid Costly Mistakes

To choose a probiotic, start with the strain, not the brand or the biggest number. A useful label names each organism in full (genus, species and a strain code such as Lacticaseibacillus rhamnosus GG), states how many live organisms remain at the end of shelf life, and tells you how to store it. The right product is the one whose exact strain and amount match what was actually tested in research for the reason you are interested in.

This guide includes a few product links near the end. As an Amazon Associate, michelle.net.au earns from qualifying purchases, at no extra cost to you.

This guide walks through a probiotic label line by line: what the strain code means, why CFU at expiry matters more than CFU at manufacture, why a higher count is not automatically better, how label rules differ between the US, Australia, the UK and EU, and Canada, and what to ask your doctor or pharmacist before you buy. It is educational only and makes no claim that any probiotic will change a health condition.

At a glance

• Strain first: research results apply to specific strains. “Lactobacillus” alone tells you very little.
• CFU at end of shelf life: live counts fall over time, so a count “at manufacture” can overstate what you actually swallow.
• Bigger is not better: the NIH Office of Dietary Supplements notes that higher CFU counts do not necessarily mean a more effective product.
• Storage matters: follow the label. Some products need refrigeration and some are made to be shelf-stable.
• Check with a professional if you are seriously ill, immunocompromised, about to have surgery, or buying for a premature baby.

What a probiotic actually is

The widely used scientific definition, from the International Scientific Association for Probiotics and Prebiotics (ISAPP) and quoted by the NIH Office of Dietary Supplements, describes probiotics as live microorganisms that, when given in adequate amounts, confer a health benefit on the host. Three words in that definition are the key to reading a label: live, adequate amounts and benefit. A label should help you check the first two, and the research behind the specific strain is where the third is tested.

This is also why “contains cultures” is not the same as “probiotic”. Fermented foods such as yoghurt, kefir and sauerkraut can contain live microbes, but unless the specific organisms and amounts have been studied, they do not automatically meet the scientific definition. That does not make them bad foods. It simply means the label claim and the evidence are two different things.

How to read the strain name

Every organism in a well-labelled product is identified at three levels. Think of it like a person’s family name, given name and identity number.

Level	Example	What it tells you
Genus	Lacticaseibacillus	The broad group. Very general.
Species	rhamnosus	A narrower group within the genus.
Strain designation	GG	The specific, identifiable strain. This is what research is tied to.

Two strains of the same species can behave quite differently, so a study on one strain does not tell you about another. If a label lists only a genus or species with no strain code, you cannot match it to any trial. Health Canada’s food labelling guidance, for example, asks for genus, species and a strain identity, and recommends using the number assigned by a recognised culture collection.

Why the names on older articles look different

In 2020 many species formerly grouped under Lactobacillus were moved into new genera, as the NIH Office of Dietary Supplements notes. So Lactobacillus rhamnosus GG is now Lacticaseibacillus rhamnosus GG. Same organism, new family name. Older research, older bottles and newer bottles may use different names for the same strain, so it is the strain code that lets you match them.

CFU: what the number means and what it does not

CFU stands for colony-forming units, an estimate of how many viable (live, able to multiply) cells are present. Labels often write large numbers in scientific shorthand: 1 x 10^9 is 1 billion CFU and 1 x 10^10 is 10 billion CFU. The NIH Office of Dietary Supplements notes that many products contain 1 to 10 billion CFU per dose, and some contain 50 billion or more.

Three points to keep in mind:

1. Look for “at end of shelf life” or “until expiry”. Live organisms die off over time. A count “at time of manufacture” may be higher than what is left by the time you use the product. The FAO/WHO working group guidelines on probiotics, later echoed in industry best-practice guidelines, list minimum viable count at the end of shelf life as one of the things a label should show.
2. Per serving, not per bottle. Check whether the CFU figure is per capsule or per serving of two or more capsules.
3. Match the amount to the research. The meaningful question is whether the product supplies the same strain at roughly the amount used in studies, not whether it has the biggest number on the shelf.

How label rules differ by country

Probiotic labels look different around the world because the rules are different. If you buy online from another country, the label may follow rules you are not used to.

Region	How probiotics are generally regulated	What that means on the label
United States	Sold as dietary supplements. Regulations require the amount of microorganisms to be listed by weight on the Supplement Facts panel.	Weight includes live and dead cells. In 2018 the FDA issued draft guidance saying it intends to allow CFU to be listed alongside the weight. Many brands now show both.
Australia	Probiotic capsules sold as complementary medicines are typically listed medicines regulated by the TGA, with an AUST L number on the pack.	The label must state the names and quantities of active ingredients. The TGA’s quality guidelines for listed probiotic medicines (put out for consultation) expect counts to meet the stated amount throughout shelf life.
European Union	Sold as food supplements under food law. The European Commission regards “contains probiotics” as a health claim needing authorisation, and no probiotic health claim has been authorised.	Many products avoid the word “probiotic” and list “live cultures” or the organism names instead.
United Kingdom	Similar food-law approach under the GB nutrition and health claims rules. The Advertising Standards Authority regards “probiotic” as a health-related claim.	You may see organism names and counts without the word “probiotic” or any benefit claim.
Canada	Probiotic capsules are generally licensed as natural health products with an NPN number. Foods follow separate Health Canada labelling guidance.	For foods making a general probiotic claim, Health Canada sets a minimum of 1 billion CFU per serving maintained through shelf life, with CFU declared at end of shelf life.

The practical takeaway: the absence of the word “probiotic” on a European or UK product is not a warning sign in itself, and a US label showing milligrams instead of CFU is following its local rules. For more on cross-border buying, see the guide to buying supplements internationally.

A line-by-line label checklist

Take this list with you, or keep it open on your phone in the shop.

1. Full name of every organism: genus, species and strain code for each one.
2. Amount per serving for each strain, or at least the total, in CFU.
3. “At end of shelf life” wording next to the count, plus a clear expiry date.
4. Serving size and directions that make sense with the amount listed.
5. Storage instructions: refrigerate, or store below a stated temperature, away from moisture.
6. Other ingredients: allergens such as milk or soy, added fibres, sweeteners and capsule material.
7. Local registration number where one applies, such as AUST L in Australia or NPN in Canada.
8. Manufacturer contact details so you can ask for strain information if it is missing.

For general label skills that apply to every supplement, the guide on how to read a supplement label covers serving sizes, active versus other ingredients and warnings.

Single strain or multi-strain?

Multi-strain products can sound more thorough, but more strains does not automatically mean more benefit. The NIH Office of Dietary Supplements summary of research on antibiotic-associated diarrhoea, for example, notes that using multiple strains showed no added benefit over single strains in that area. Multi-strain products can also be harder to judge, because each strain may be present in a much smaller amount than the headline total suggests, and the combination itself may never have been tested.

Question	Single-strain product	Multi-strain product
Can you match it to research?	Often easier, if the strain code is listed	Only if the exact combination, or each strain at its own amount, was studied
Is the per-strain amount clear?	Yes, the total is the strain amount	Not always; some labels give only a total
Is it simpler to compare?	Yes	Harder

What studies have tested, in brief

Research on probiotics is large and mixed, and results are specific to strains, doses and groups of people. The NIH Office of Dietary Supplements fact sheet summarises it cautiously. For antibiotic-associated diarrhoea, the most consistent findings in that summary were for Lacticaseibacillus rhamnosus GG or the yeast Saccharomyces boulardii, started within two days of the first antibiotic dose, in children and in adults aged 18 to 64. A benefit was not seen in adults aged 65 and older. For irritable bowel syndrome, the fact sheet describes possible modest effects on some symptoms that depend on strain and symptom, and calls for better trials.

Two lessons follow. First, results in younger adults cannot simply be assumed for older adults. Second, a study on one strain does not support a different strain, which is why the strain code matters so much. If you are thinking about a probiotic for a particular reason, talk to your doctor or pharmacist about which strains, if any, have been studied for it.

Who should check with a professional first

The NIH Office of Dietary Supplements says probiotics are unlikely to cause harm in healthy people and that side effects are usually minor. It also notes rare reports of serious bloodstream infections, mostly in people who were severely ill or immunocompromised. In 2023 the US FDA warned that probiotics given to premature infants may cause serious infection.

Talk to your doctor or pharmacist before using a probiotic if you:

• have a weakened immune system, including from chemotherapy or medicines that suppress the immune system
• are seriously ill, in hospital, or have a central line or recent surgery
• are buying for a premature or very young baby
• take other medicines and want to check timing, especially antibiotics

Who a probiotic supplement suits, and who it may not

May suit: people who want to try a specific, well-studied strain for a reason their doctor or pharmacist agrees is reasonable, and who are happy to store it properly and use it consistently for a set trial period.

May not suit: people looking for a general “gut health” fix without a specific reason, people in the higher-risk groups above without medical advice, and anyone hoping a probiotic will stand in for a varied diet. Eating a range of plant foods supplies fibre, which gut microbes use as fuel; the guide to dietary fibre sources and labels explains how to read fibre on food packs.

A worked example: comparing two labels

Imagine two capsules on the same shelf.

• Product A: “50 billion probiotics, 12 strains”. The ingredients list genus and species names only. No strain codes. No statement about when the count was measured. “Store in a cool, dry place.”
• Product B: “Lacticaseibacillus rhamnosus GG, 10 billion CFU per capsule at end of shelf life”. Refrigerate after opening. Expiry date printed.

Product A has the bigger number, but you cannot match any of its twelve organisms to a study, you do not know how much of each strain is present, and you do not know whether 50 billion is still alive at expiry. Product B gives you exactly what you need to look up the research and check whether the amount lines up. On label quality alone, Product B is the easier choice to judge, even though it looks smaller.

Common mistakes to avoid

• Buying on CFU alone. The highest number is not a measure of quality or effect.
• Ignoring the strain code. Without it, the product cannot be linked to any research.
• Storing it wrongly. Heat and moisture can reduce live counts. A product that says refrigerate should go straight in the fridge.
• Assuming results in younger adults apply after 65. Some research has found differences by age group.
• Switching products constantly. If you and your health professional decide to try one, give it a defined trial period and note any changes, rather than changing brands every week.
• Reading seals as proof of benefit. Quality seals may confirm what is in the bottle, not whether it will help you. The guide to supplement certification seals explains what each one checks.

Questions to ask your doctor or pharmacist

1. Is there a specific strain that has been studied for my situation, and at what amount?
2. Is a probiotic safe for me with my current health conditions and medicines?
3. If I am taking antibiotics, how should I time a probiotic around them?
4. How long should I try it before deciding whether it is worthwhile?
5. What changes should prompt me to stop and check in?

For the bigger picture on deciding whether any supplement is worth buying, the supplements evidence and label guide brings together how to weigh research, read labels and avoid wasting money.

Sources this guide draws on: the NIH Office of Dietary Supplements probiotics fact sheet for health professionals; ISAPP’s guidance on decoding probiotic labels and the FAO/WHO guidelines for the evaluation of probiotics in food; the US FDA’s 2018 draft guidance on labelling dietary supplements containing live microbials and its 2023 warning about probiotics in preterm infants; TGA guidance on the quality of listed probiotic medicines; Health Canada’s guidance on health claims about microorganisms and the term “probiotic”; the European Ombudsman decision on the Commission’s interpretation of “probiotic” under EU claims law; and UK Advertising Standards Authority advice on probiotic claims.

Frequently asked questions

How many CFU should a probiotic have?

There is no single right number, because useful amounts depend on the strain and what it was studied for. Many products contain 1 to 10 billion CFU per dose, according to the NIH Office of Dietary Supplements, and higher counts are not necessarily more effective. Look for the amount used in research on that exact strain, stated at the end of shelf life.

Do probiotics need to be refrigerated?

Some do and some do not. It depends on the organisms and how the product is made and packaged. Follow the storage directions on the label exactly, and keep any probiotic away from heat and moisture.

What does a strain code such as “GG” mean?

It identifies the specific strain within a species. Research results are tied to strains, so this code is what lets you match a product to a study. A label without strain codes makes that impossible.

Is a multi-strain probiotic better than a single strain?

Not automatically. More strains can mean less of each one, and the combination may not have been tested. In some research areas summarised by the NIH, multiple strains showed no added benefit over a single strain.

Why doesn’t my European probiotic say “probiotic” on the pack?

In the EU, regulators regard the word “probiotic” on foods and food supplements as a health claim that needs authorisation, and none has been authorised. Many products there list the organisms or say “live cultures” instead. The UK has a similar approach.

Is it safe to take a probiotic after 50?

For healthy people, the NIH describes probiotics as unlikely to cause harm, with usually minor side effects. Risks are higher for people who are seriously ill or immunocompromised. If you have ongoing health conditions or take several medicines, talk to your doctor or pharmacist first.

A good probiotic label does the hard work for you: a full strain name, a live count at expiry, clear storage and a sensible serving. If a product cannot tell you those things, it is fair to move on, and a short conversation with your pharmacist will often get you further than any number on the front of the box.