What are CFUs

Written by: Kari Raman, PharmD, RPh
Published March 29, 2023

CFUs, or colony-forming units, is a unit of measurement that represents the number of live, viable microorganisms, such as bacteria or yeasts, present in a probiotic supplement. The CFU count provides an estimate of the concentration of active probiotic organisms in a dose or serving product. The higher the CFU count, the greater the number of potentially beneficial bacteria in the probiotic. When choosing a probiotic supplement, it is essential to consider the CFU count, as well as the specific strains of bacteria included and their potential health benefits.

But, bigger is not always better – it’s all about the right dose.

It’s very tempting to want a higher count! But that’s not always what you want when taking a probiotic supplement. Too many can actually be bad; you can overwhelm your digestive system, which can cause unpleasant to serious symptoms (gas and bloating on the unpleasant end, and actual severe problems on the serious end). 

So don’t just go for the highest number. 

The effectiveness of a probiotic depends on several factors, such as:

Strain specificity: Different strains of bacteria may have different health benefits. Therefore, it’s important to choose a probiotic supplement containing strains that have been scientifically proven to support the health benefits you’re seeking.

Quality and stability: The quality of the probiotic and its ability to remain stable and viable throughout its shelf life are essential. Look for reputable manufacturers that guarantee the CFU count until the product’s expiration date.

Individual needs: The optimal colony-forming unit count can vary depending on an individual’s specific needs, health conditions, and the probiotic’s intended use. For some people, a lower count may be sufficient, while others may require a higher number.

Tolerance: Some individuals may experience gastrointestinal discomfort with a high CFU count, especially if they are new to taking probiotics. In such cases, it may be better to start with a lower CFU count and gradually increase as needed.

When choosing a probiotic, it’s essential to consider these factors and consult with a healthcare professional for personalized advice on the appropriate probiotic supplement and CFU count for your specific needs.

How many colony-forming units of probiotics should you take a day for a healthy gut

There is no one-size-fits-all answer for the ideal daily CFU count of probiotics for maintaining a healthy gut, as it can vary depending on your individual needs and specific probiotic strains. However, general guidelines suggest that a daily dose of probiotics should contain at least 1 billion to 10 billion CFUs (maybe 15 billion on the high end) for general gut health and maintenance.

Again, talk with your doctor about the right dose of probiotics to help you treat specific conditions or maintain a healthy gut.

Another factor in determining how many CFUs you need is how accurate the supplement bottles are in their labeling! Which leads us to another question:

How accurate are probiotic supplements in labeling the CFUs in their products

Unfortunately, many probiotics are not very accurately labeled – probably due to poor manufacturing and shipping. The accuracy of CFU labeling on probiotic supplements can vary widely among different manufacturers and products. I read a depressing study that said that, for veterinary probiotics, the quality control is pretty poor. In this study, they looked at 25 veterinary probiotics and found only 2 had the same amount and type of bacteria as was listed on the product! 

Some companies are diligent about ensuring that their products contain the stated CFUs and maintain quality control throughout the manufacturing, storage, and distribution processes. However, there have been instances where independent testing revealed discrepancies between the labeled CFU counts and the actual number of viable microorganisms in the products, such as that study I just mentioned. 

To increase the likelihood of choosing a high-quality probiotic supplement with accurate CFU labeling:

  1. Look for reputable brands: Choose products from well-established, reputable companies known for their commitment to quality and scientific research.
  2. Check for third-party testing: Some probiotic supplements undergo independent testing and certification by third-party organizations (such as NSF International or ConsumerLab) to verify their potency, purity, and accuracy of labeling.
  3. Examine the label: Look for a guaranteed CFU count through the product’s expiration date, not just at the time of manufacture, as this provides a better indication of the supplement’s stability and potency over time.

Finally, you need to store your probiotics correctly so that the live organisms don’t die.

Many probiotics need to be stored in the refrigerator because the live microorganisms they contain are sensitive to temperature, humidity, and other environmental factors. Refrigeration helps maintain the viability and potency of these beneficial bacteria by providing a cool and stable environment that slows down their metabolic processes and reduces the risk of degradation. Check the label on your product, or ask your pharmacist.


So, getting the right amount, or CFU, of your probiotic supplement matters. But it also matters that you are using a quality product that has been properly stored – and that you are using the right species for your specific needs. Read more of our tips on getting the most out of probiotics, including info on what time of day you should take your probiotics and how long probiotics take to work.

What Are Probiotics and Why CFUs Matter?

At the pharmacy, I explain to patients that probiotics are live microorganisms that may be able to give you ceratins health benefits, especially for our digestive system. The human body, fascinatingly, is a complex ecosystem where both beneficial and harmful bacteria coexist. The “good” bacteria, or probiotics (sometimes yeast, to be totally honest), play a pivotal role in maintaining this delicate balance.

Different strains of these beneficial bacteria may provide varied health purposes. For example, Lactobacillus might be your ally against diarrhea or lactose digestion woes, while Bifidobacterium present in some foods can be instrumental for those grappling with irritable bowel syndrome (IBS). Note that the most recent systematic review on IBS that I’ve read suggests that having a combination of probiotics will be best for trying to treat IBS.

Beyond just gut health, these microorganisms have a more extensive resume. They’ve been linked to heart health, mental well-being, bolstering the immune system, and even mitigating certain allergies and eczema. The science is still emerging, so it’s not 100% clear that all the supposed health benefits are going to actually be real, but the good news is that for healthy people, in the right doses, they are usually safe to take as directed. 

It’s also important to note that while our bodies naturally harbor these helpful bacteria, they can also be introduced through certain foods and supplements. Think yogurt with live cultures, or fermented delights like sauerkraut, kimchi, or kombucha. 

But with the vast array of probiotic products available, it’s essential to be discerning. Understanding CFUs can guide you in this. And while it’s tempting to think “the more, the merrier,” that’s not always the case. Balance is key. Too high a CFU count might not suit everyone and can sometimes lead to gastrointestinal discomfort.

In wrapping up, it’s clear that probiotics, with their myriad benefits, deserve their spotlight in the realm of health and wellness. They are nature’s little helpers, working tirelessly behind the scenes to ensure our bodies function optimally. When choosing to supplement, pay heed to CFUs, consider the strains you’re getting, and always be guided by quality. And remember, when in doubt, always consult with a health professional to tailor choices to your unique needs. One supplement I recently wrote a review of is Good Girl Probiotics.

Pharmacist Kari Raman

I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

Probiotics are confusing!

One of the most common questions I get asked by patients is about probiotics. And the truth is, probiotics are not as well understood by the healthcare community as they should be.

So I’ve been reading a lot of probiotic clinical trials, and sharing what I’m learning here.

I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!