How Many CFU Do You Need in a Probiotic?

The short answer: No official CFU number exists for a probiotic. The NIH Office of Dietary Supplements (ODS) reports that official recommendations for healthy people's probiotic use don't exist, and it says a higher count alone doesn't necessarily bring more benefit, because the specific strains matter too. So how many CFU a probiotic needs starts with which microbe it holds. The four compared here print 10 billion to 40 billion CFU per serving.

Key takeaways

• No federal source we read sets a daily CFU target for healthy people, so a "you need X billion" line is marketing, not a rule.
• A CFU count only means something next to the microbes it counts.
• The milligrams printed beside a probiotic aren't a CFU count, and two of our strips list different weights for the same 10 billion.
• When a blend lists many microbes under one total, the label doesn't say how that total is shared.
• For a healthy adult, "too much" on a probiotic label means more than its suggested use, and people who are very ill or have weak immune defenses should ask a provider first.

We sell all four probiotics compared here, and two of them share the same 10 billion count. They sit on our gut health shelf, so we have every reason to want you to like our numbers. We'll show you how to read them without ranking them.

How many CFU should a probiotic have?

A probiotic has no official CFU target, because no federal source we read recommends any amount of probiotics for healthy people.

That's where the ODS probiotics fact sheet for consumers leaves it. Rather than a number, it offers a pairing: any benefit a product has depends on which microorganisms it holds and how many CFUs, taken together. So a count without a named microbe is only half the story.

The National Center for Complementary and Integrative Health (NCCIH) is just as frank. Its probiotics page says that in most cases, researchers still don't know which probiotics help, how much people would need to take, or who is most likely to benefit.

So when a brand says you need a certain count, ask what the figure rests on. Our guide to reading strain names on a probiotic label shows why the strain deserves as much of your attention as the count.

What does 10 billion CFU mean?

10 billion CFU means the label counts 10,000,000,000 colony-forming units in one serving. A colony-forming unit is a lab count of live cells, or small clumps of cells, that can grow into a visible colony.

So the figure is an estimate, not a head count: a clump that grows into one colony counts once, and cells that can't grow don't count.

The first two rows are the example amounts ODS says you might see on a label, and it writes them both ways. What neither can show is which row suits you, because that depends on the microbes, not the zeros.

Also check what the count belongs to: a serving, not always a pill. Our Probiotic & Prebiotic Capsules list 40 Billion CFU per 2-capsule serving, so read the serving size line before the count.

How many CFU of probiotics per day?

The number of CFU of probiotics you take per day is set by your label's suggested use, since the federal pages we read give healthy people no daily amount.

ODS suggests asking a health care provider what dose to take, and the label's figure is a fair place to start that talk.

The last column is each label's whole day, because none of the four asks for a second serving. Those numbers aren't rungs on a ladder, either. They belong to four different products, and each label caps you at its own serving with the line "Do not exceed recommended dose."

Only the Probiotic & Prebiotic label spreads its count across the day, and its 40 billion describes the pair of capsules, not either one. For timing the others, our guide to the best time of day for a probiotic takes that up.

Stacking two products to reach a bigger total gives you two sets of directions, not one combined target. The ODS consumer guide Dietary Supplements: What You Need to Know ties side effects mostly to high doses and to taking lots of supplements together. Our guide to taking two probiotics a day walks through that choice.

Is 10 billion CFU enough?

Whether 10 billion CFU is enough can't be settled by the number itself, because there's no official target to measure it against.

ODS lists 10 billion as one of its two example label amounts, and nothing federal we read marks it as low.

A better test is what the 10 billion is made of. Our two strips at that count show why:

• On the 10 Billion CFU Probiotic Strips, the only microbe is Bifidobacterium lactis: 37.5mg (10 Billion CFU) per 1 Oral Strip (180 mg) serving, next to 50 mg of polydextrose.
• The Probiotic & Digestive Enzyme Strips list Bacillus coagulans at 50 mg (10 Billion CFU) per 1 Oral Strip (210 mg) serving, with protease (10 mg), papain (15 mg) and bromelain (15 mg).

Same count, different microbe, different product. Neither strip prints a strain code, only the species, and that's the honest limit of both labels.

So if a 10 billion label names a microbe you chose on purpose, a bigger number on a different blend isn't an upgrade. It's a different product.

From our shop: 10 Billion CFU Probiotic Strips — one mixed berry strip a day, dissolved on the tongue, with Bifidobacterium lactis listed at 37.5mg (10 Billion CFU) in each.

Is 40 billion CFU too much?

40 billion CFU isn't too much by any federal number we found, since the ODS probiotics fact sheet sets no CFU limit.

For a healthy adult, too much means going past the label's suggested use, while someone who is seriously ill or has weak immune defenses should ask a provider before taking any amount.

On side effects, ODS lists gas as a possible effect in healthy people and says other problems are rare. It doesn't tie that to a CFU level, so we won't either. If a new probiotic doesn't agree with you, stop and ask a healthcare provider rather than guessing at a new amount.

The fact sheet doesn't cap 50 billion or 100 billion CFU labels either, and it doesn't say they do more. A 40 billion label isn't a stronger 10 billion one, just a separate formula.

What else on a probiotic label changes what the CFU tells you?

Three details change what a probiotic's CFU number tells you: the weight printed beside it, how a blend shares its total, and the footnotes and front-panel wording around it.

How many mg is 10 billion CFU?

There's no fixed number of milligrams in 10 billion CFU, because weight and count measure different things. ODS calls the CFU number the more accurate picture of active microorganisms.

Weights and counts don't move together here. The two strips print the same count at different weights, and the 800 mg blend weighs more than 20 times the strip's 37.5mg while printing 4 times its count. So milligrams can't be converted into CFU, and a heavier line doesn't mean more live microbes.

How is a blend's total CFU shared?

A blend's total CFU is shared across every microbe it lists, and neither of our blend labels says how that total is split.

Multi-Strain Probiotic Capsules list a 13 Strain Probiotic at 317 mg (20 Billion CFU) per 1 Capsule serving, then name 13 microbes by genus and species. Dividing 20 billion by 13 gives about 1.5 billion each, but that assumes an even split the label never states.

Probiotic & Prebiotic Capsules print an 800 mg Proprietary Blend of Probiotic Bacteria (40 Billion CFU) per 2-capsule serving. Under it sit MAKTREK® (Bi-Pass Technology) and four coded strains: Lactobacillus acidophilus La-14, Bifidobacterium lactis Bl-04, Lactobacillus plantarum Lp-115 and Lactobacillus paracasei Lpc-37. In the naming system ODS describes, the first word is the genus, the second the species, and a code like La-14 marks the strain. Even so, the four share one total.

What do the footnote marks and front tiles tell you?

The marks on a probiotic row send you to footnotes, and the big number on the front of a bottle may count one capsule or a whole serving.

On all four panels, one mark carries the same news: "Daily Value (DV) not established." The strips use a dagger (†) and the capsules use asterisks.

The Multi-Strain panel adds a second mark. Its "20 Billion CFU****" leads to a footnote saying the count was taken "at the time of manufacture," and that footnote is unique among these four panels. Our guide to probiotic storage and the fridge question explains what that wording does and doesn't promise.

The Multi-Strain bottle's tile reads "20 BILLION Live CFU Per Capsule," while the Probiotic & Prebiotic tile reads "40 BILLION CFU Per Serving," and that serving is 2 capsules. Side by side, the fronts suggest a twofold gap. Halving the serving gives 20 billion a capsule on paper, but that's our arithmetic, not a printed figure, and the two blends hold different microbes anyway. Put counts on the same basis first, then compare what they're counting.

From our shop: Probiotic & Prebiotic Capsules — two capsules a day, one by day and one in the evening per the label, holding an 800 mg blend of four coded strains plus MAKTREK® listed at 40 Billion CFU.

Do you need a higher CFU count if you already eat fermented foods?

Eating fermented foods doesn't call for a higher CFU count, because there's no official daily total for food and supplements to add up to.

ODS names plenty of foods made with microorganisms, including cheese, pickles and sourdough bread. Then it adds a caution: being made that way doesn't mean a food necessarily carries probiotics with proven health benefits. So a slice of sourdough or a pickle spear isn't a CFU serving you can count, and there's no gap for a bigger capsule to fill.

It's fine to skip a probiotic, or wait, if:

• An ad saying your count is too low is the only reason you're shopping.
• You already take one and planned a second only to push the total higher.
• A daily serving, the way the label asks, isn't something you'll keep up.

Who should check with a healthcare provider first?

Talk with a doctor or pharmacist before you start a probiotic if you're pregnant or nursing, younger than 18, taking a medication, having surgery soon, or living with a medical condition.

• These four labels share one caution, word for word: "Consult a physician if pregnant, nursing, under 18, or have a medical condition."
• NCCIH suggests talking with your health care provider before you try a probiotic supplement, and wants anyone with a serious underlying health condition watched closely while they use one.
• ODS flags possible problems for anyone already seriously ill or living with a weak immune system.
• ODS's supplement guide adds that a label's serving is the maker's suggestion, and your provider may set a different amount for you.

Bring the product, or a clear photo of its Supplement Facts panel, so your provider sees the exact microbes and count.

FAQ: probiotic CFU counts

Is 1 billion CFU enough?

Whether 1 billion CFU is enough depends on the microbe behind it, not the count alone. ODS uses 1 billion as one of its example label amounts. Our Apple Cider Vinegar & Probiotic Capsules list Lactobacillus acidophilus LA85 at 10 mg (1 Billion CFU) per 2-capsule serving, counted at the time of manufacture, beside 1,000 mg of organic apple cider vinegar powder.

How many CFU are in yogurt?

There's no single CFU figure for yogurt, because it depends on the product and whether its label gives a count at all. ODS explains that yogurt is made by adding live microorganisms, such as Lactobacillus bulgaricus and Streptococcus thermophilus, to milk. It also says a food that contains probiotics should list their genus, species and strain on the label.

How many CFU should a woman take?

No federal source we read sets a separate CFU amount for women. These four labels give one serving with no directions that differ between women and men. A probiotic marketed to women still answers the same two questions as any other: which microbes it lists, and how many CFU per serving. If you're pregnant or nursing, each of these labels asks you to consult a physician first.

Can kids take a 10 billion CFU probiotic?

Our 10 billion CFU strips ask anyone under 18 to see a physician first, so they aren't a product to give a child on your own. ODS also notes the FDA has reported that probiotics might cause life-threatening illness in preterm infants. A child's probiotic, and its count, is a decision to make with a pediatrician, not by cutting down an adult serving.

Is CFU the same as the number of strains?

No, CFU and strain count measure different things. CFU counts live units that can grow into colonies, while a strain count tells you how many kinds of microbe a label lists. Multi-Strain Probiotic Capsules put 13 kinds under one 20 Billion CFU total, and the 10 Billion CFU Probiotic Strips give half that count from a single species. A longer list doesn't raise the total, and a bigger total doesn't add kinds.

Sources

• Probiotics: Fact Sheet for Consumers (NIH Office of Dietary Supplements)
• Probiotics: Usefulness and Safety (NCCIH)
• Dietary Supplements: What You Need to Know (NIH Office of Dietary Supplements)

If this left you looking for somewhere to start, read 10 billion CFU probiotic strips — its amounts per serving are listed on the page. For the practical questions this raises, how dosing, sourcing and subscriptions work is answered in one place.