Iron Supplements and Probiotics: What You Need to Know, According to a Gut Health Dietitian

Can you take iron supplements and probiotics together? 

Can probiotics reduce the awful side effects of iron pills for people with iron-deficiency anemia?  

Does iron feed bad bacteria? 

Why does iron make people constipated? 

Is it possible to take iron pills without getting sick?

…If you’ve asked yourself any of the above questions, and/or you’re hoping to learn more about iron supplements and probiotics… you’re in the right place!  

As a functional dietitian nutritionist who specializes in irritable bowel syndrome (IBS), leaky gut, dysbiosis, and micronutrient deficiencies (including iron deficiency anemia), I’ve got you covered! I promise to answer all of your questions related to iron and probiotics (and more) in this article.

I also happen to be a clinical nerd who LOVES to go off the deep end when it comes to talking about these kinds of things… so buckle up! 😉

Iron 101

Iron is a type of mineral from the periodic table of elements, and it’s also a vital micronutrient which we need in certain amounts in order to live.  

From helping out with the synthesis of genetic material like deoxyribonucleic acid (aka “DNA”) to electron transport, iron is pretty important!

Another big role that iron plays in the body is to help make red blood cells, which are responsible for transporting oxygen and nutrition to every cell in the body.  (Kind of a big deal!)

Most people are able to get enough iron from food, iron-rich herbs, and/or iron pills / supplements as needed.  (In more extreme cases, people can also get iron via iron infusions or blood transfusions as a last-resort.)

  • When people don’t get enough iron or when the body is losing iron faster than it can be replaced, this can lead to a condition called iron-deficiency anemia.

Before we dive any further into iron or anemia, let’s first talk about gut health and probiotics for a few minutes.

Gut health 101

“Gut health” is referring to the state of your gastrointestinal (GI) tract, aka your gut, which is a tube-like structure in the digestive system which serves as your barrier between the outside world and the inside of your body.  

  • The gut includes the mouth, esophagus, stomach, intestines, colon, and rectum. Some have said we may even have enough “gut” tissue to cover an entire tennis court!

Our gut is a major organ responsible for breaking down and extracting (“digesting”) the nutrients we need from food, leaving the rest to be eliminated as waste.

Why does gut health matter?

Aside from digesting food and absorbing nutrients, our gut is intimately connected to lots of other important functions, including but not limited to: vitamin and mineral absorption, detoxification, immune balance, cognitive function, mood/mental health, hormonal regulation, skin, and more!

Long story short: a healthy gut is generally correlated with good health and a better quality of life, while an unhealthy gut can and will lead to other issues if left unchecked.

A major factor which can make-or-break our state of gut health is the “microbiome”, which also happens to be impacted by both iron supplements and probiotics.

What is a microbiome?

A microbiome is each individual person’s unique ecosystem of microbes such as bacteria, yeast, fungus, and viruses in the body. 

While microbes are technically found all throughout the body (such as in the skin, ears, eyes, lungs, etc.), the majority of our microbiome “lives” in the gut – mostly in the colon.

  • It’s been said that we have more than 100 trillion microbes in the gut alone (1) and that we have roughly 10x more microbes than we do human cells! Wowzah… 

Your ecosystem of microbes living in your gut are collectively referred to as your “gut microbiome.”  We can have both good microbes (probiotics) and bad “dysbiotic” microbes in the gut.


You may have heard the word “probiotics” tossed around a lot in conversations nowadays, as probiotics have become a trending supplement in my world of nutrition and gut health!

Probiotics are healthy, beneficial types of bacteria and yeast that live in the body, mostly in the gut. 

  • That’s right – not all yeast and bacteria are bad!  In fact, probiotic microbes are considered to be “symbiotic”, which means we have a mutually beneficial relationship dynamic going on.
    • We lean on probiotic microbes just as much as they lean on us to function and thrive. 

Probiotics offer lots of benefits such as making vitamins, helping us digest our food, helping to nourish and protect our gut lining, fighting off “bad” microbes, and keeping pH acidity levels regulated in our gut for optimal digestion, to name a few.

Unfortunately, however, just like humans, not all microbes in our gut are good, which leads me to “dysbiosis”…

What is “dysbiosis”?

Dysbiosis is a functional medicine term which describes a state of imbalanced gut flora in the microbiome. (Keep in mind: unlike IBS or IBD, dysbiosis is not a medical condition!)

For example, a “dysbiotic” gut is one in which there aren’t enough “good” guys, (which often happens after a round of broad-spectrum antibiotics), which then in turn allows for more “bad” or “opportunistic” microbes to start over-growing out of control.

Troublesome strains of bacteria and yeast are usually hidden culprits of unwanted symptoms like abdominal pain, inflammation, nausea, constipation/diarrhea, gas, and/or bloating in the gut – especially when they grow out of control.

  • “Dysbiotic” microbes are basically the troublemakers.

As if that wasn’t bad enough, these types of “dysbiotic” microbes compete with us to get nutrition from the food we’re eating, and they can even hook onto the gut wall and leech nutrients out parasitically. 

While this sounds pretty mortifying, in this modern-day world, many people are walking around in some kind of dysbiosis and they don’t even realize it!

Now that you’re up to speed on iron, gut health, probiotics and dysbiosis, let’s hone in on how iron interacts with our gut microbes.

Iron supplements and IBS: the “dark side” of iron pills

While taking iron supplements properly can be a very effective way to correct an iron deficiency, there’s a dark side to going this route:  iron supplements are infamous for causing unwanted side effects and “collateral damage” which could show up as nausea, vomiting, constipation, dysbiosis, and worst-case scenarios, even a bowel obstruction (2). 

So at this point you’re likely wondering, why does iron cause so many gut issues?!

Frequently asked questions 

Let’s deep-dive into some common questions I often hear about iron and probiotics…

(Keep in mind: this information isn’t customized, and it isn’t medical advice, so make sure to always consult your healthcare team in conjunction with these articles!)

Iron pills and the microbiome: does iron feed bad bacteria?

While the jury is still out and researchers are still saying the root causes of these side effects are unclear, we know for sure that the unabsorbed iron from iron pills will feed “bad” (pathogenic) microbes in the gut (3, 4)… which, as we now know, alters the gut microbiome for the worse. 

  • In many cases, it’s safe to assume that supplementing with iron pills can and will often feed “bad” dysbiotic microbes!  
    • And in the functional nutrition community, we know that dysbiosis is an underlying root cause of IBS and other types of gut issues.

(If you’re prone to IBS and/or unwanted side effects from iron pills, you may be interested in checking out this herbal iron syrup recipe!)

The state of our gut microbiome (for better or worse) can also help or hurt our ability to absorb iron from food…

Can probiotics cause iron deficiency?

This can be confusing!  It’s a bit of a “chicken or the egg” phenomenon, since many people who take probiotics also happen to be iron deficient.  So do probiotics cause iron deficiency, or is it something else?

Contrary to this common misconception probiotics actually seem to increase and enhance iron absorption, according to a recent Nutrients journal study from 2020! (5)

  • Iron absorption was enhanced among all the different groups of people with iron-deficiency anemia who added various types of probiotic strains into their diet and supplement routines.

All of that said, it’s more likely that poor gut health (such as in cases of IBS, IBD, leaky gut, and dysbiosis) is what’s to blame when it comes to iron deficiency.  And lots of people with gut issues tend to take probiotics!

Probiotics and iron absorption: how it works

Probiotic supplements seem to enhance iron absorption because certain strains of probiotics release substances called “short-chain fatty acids” (a type of “post-biotic” produced by good microbes) which can help to regulate and optimize the acidity level in the colon, making it easier for iron to get into the bloodstream. (5)

How can I take iron pills without getting sick?

While there’s always a risk of getting constipated or nauseous from iron supplements, taking a probiotic at the same time may help to reduce the GI “aftermath” from your supplements.

And of course make sure to always take iron pills or iron-containing multivitamins / prenatal vitamins with food!

It may also be worth asking your doctor, dietitian, and herbalist about the possibility of exploring blood-building, iron-rich herbs as a safer alternative to iron pills.

Can I take iron and probiotics together? 

Not only is it safe to take iron supplements and probiotics together – it’s encouraged! 

Taking iron and probiotics together with a meal is your best bet when it comes to optimizing your gut microbiome while also reducing the likelihood of feeling sick afterwards.

(Just make sure you aren’t having iron with yogurt, which is high in calcium and can reduce iron absorption.) 😉

How can I increase iron absorption from non-heme iron?

If you’re taking iron pills, this is non-heme iron which requires vitamin C in order to convert into the bioavailable form (heme iron).

Consider taking iron supplements with orange juice or herbs high in vitamin C.

Also make sure NOT to take iron at the same time as calcium (or calcium-rich foods/herbs) since this will block iron absorption.

Is Yakult good for anemia?

No, but it isn’t bad for anemia as long as you are taking it at least a few hours apart from iron supplements or iron-rich foods/herbs.

(Yakult is a type of milk-based yogurt drink which contains calcium.  Calcium and iron compete for the same absorption sites in the gut.)

TLDR:  The calcium in Yakult may potentially reduce the iron absorption from your iron-rich foods/herbs/supplements. Don’t take your iron supplements with Yakult!

More resources

For more information on iron, the gut microbiome, and/or probiotics, feel free to check out the following articles:

Iron deficiency anemia

Probiotics and prebiotics


  1. Altveş, Safaa et al. “Interaction of the microbiota with the human body in health and diseases.” Bioscience of microbiota, food and health vol. 39,2 (2020): 23-32. doi:10.12938/bmfh.19-023
  2. Parvataneni, Swetha, and Min Maw. “Ileus Due to Iron Pills: A Case Report and Literature Report on the Importance of Stool Softeners.” Cureus vol. 12,6 e8392. 1 Jun. 2020, doi:10.7759/cureus.8392
  3. Yilmaz, Bahtiyar, and Hai Li. “Gut Microbiota and Iron: The Crucial Actors in Health and Disease.” Pharmaceuticals (Basel, Switzerland) vol. 11,4 98. 5 Oct. 2018, doi:10.3390/ph11040098
  4. Jaeggi, Tanja et al. “Iron fortification adversely affects the gut microbiome, increases pathogen abundance and induces intestinal inflammation in Kenyan infants.” Gut vol. 64,5 (2015): 731-42. doi:10.1136/gutjnl-2014-307720
  5. Rusu, Ioana Gabriela et al. “Iron Supplementation Influence on the Gut Microbiota and Probiotic Intake Effect in Iron Deficiency-A Literature-Based Review.” Nutrients vol. 12,7 1993. 4 Jul. 2020, doi:10.3390/nu12071993

6 thoughts on “Iron Supplements and Probiotics: What You Need to Know, According to a Gut Health Dietitian”

  1. Hi Jenna,

    What are your thoughts about this habit: taking a pill of iron with orange juice (or anything with vitamin C) every other morning, and alternating with a probiotic with yogurt on the remaining days, based on the review you did on this subject?

    Thank you.

    1. Jenna Volpe, RDN, LD, CLT

      Hi Georgie, that’s a great question!
      Generally, I think that habit could potentially work from a standpoint of optimizing iron levels while also maintaining healthy microbes in your gut from a probiotic standpoint.
      It depends on your iron supplement dose, your body’s iron levels, and the state of your gut microbiome as well as your overall diet.
      For iron absorption, the key is to make sure you’re taking iron with vitamin C and not with calcium-rich foods like yogurt.
      These are all factors that can be discussed in a 1-1 consultation with a registered dietitian.
      All of that said, make sure to consult with your healthcare team to verify whether or not this habit is in your best interest. 😉

    1. Jenna Volpe, RDN, LD, CLT

      Hi Mary, great question! It’s generally not ideal to mix iron supplements with calcium-rich foods/drinks like milk, yogurt or kefir as this can potentially reduce the iron absorption.

      You may want to check out this article for more details on how this happens:

      But either way, make sure to consult with your doctor/registered dietitian to receive customized advice around this! -Jenna

  2. Excellent article. Answered my question and made me smarter about what I’m going through. I love your writing style, too. Thank you !!

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