What if low iron isn't the diagnosis, but the clue?
A low iron result can look simple: replace the iron, watch the number improve, and move on. But sometimes the most important question isn't how to raise the number. It's why the iron became low in the first place.
In this episode of Rise Above, I’m going beyond the CBC to explain what iron actually does, why ferritin matters, and why women in their 40s and 50s can become especially vulnerable to depleted iron stores. We’ll also talk about heavy periods, gut absorption, supplementation, constipation, high ferritin, and the testing that can help you see the bigger picture.
I also share a patient story that permanently changed the way I think about unexplained iron deficiency and why treating an abnormal lab should never replace investigating its cause.
The goal isn't simply to make a lab value look better. It's to understand what that lab value may be trying to tell you.
What if I told you that a routine blood test holds one of the biggest clues to a stage IV cancer... and in one particular case of mine... it was missed for over a year!!!
Let me tell you about a patient I saw - a man in his mid-fifties.
About a year before we met, his employer ran routine wellness labs. His iron came back low. His primary care doctor started him on an iron supplement.
Two months later, they repeated his labs. His iron had improved. The supplement was stopped. No further follow-up was recommended.
And no one asked the question that mattered most.
Why did a healthy man in his fifties need iron in the first place?
That question would change everything.
When he came into my office, he mentioned something almost in passing. For nearly a year, he'd been dealing with this uncomfortable fullness in his upper abdomen. He said he could never quite finish a meal because he felt full so quickly.
That immediately caught my attention.
So I asked him a question I ask a lot.
“Have you noticed any blood in your stool?”
He said no.
So I asked it a different way.
“Has it ever looked like coffee grounds?”
He paused.
Then he said, “...Actually... yes.”
When we met again for his report of findings, he admitted that yes, he had been seeing blood.
I never started him as a patient. Instead, I referred him directly to a gastroenterologist.
Four weeks later, my phone rang. It was his fiancée.
He had been diagnosed with stage IV colon cancer. He was starting chemotherapy that week. He was also putting his end-of-life documents together.
That phone call has stayed with me ever since.
Because here's what I think about every time I see someone with low iron.
His iron wasn't ignored. It was treated. His numbers improved. The supplement worked.
But the question that mattered most was never answered.
Why was a healthy man in his fifties iron deficient in the first place?
Because iron deficiency isn't the diagnosis. It's the clue.
Now, to be clear, most people with low iron do not have colon cancer. But unexplained iron deficiency - especially in men and postmenopausal women - deserves an explanation, not just a prescription.
That philosophy - never stopping at the abnormal lab, but asking why it became abnormal - is the foundation of how I practice medicine.
Today, we're going to talk about what iron actually does in your body, why so many women in their 40s and 50s end up deficient, what your iron labs are really telling you, and how to think about supplementation the right way instead of simply guessing.
I'm Dr. Emily Wheeler, and this is Rise Above.
Let's start with what iron actually is, because I think this is where a lot of the confusion begins.
The word “heme” - as in hemoglobin - comes from the Greek word haima, which simply means blood. Hemoglobin is heme plus a protein called globin, and sitting right in the center of that heme molecule is iron.
Here's a simple way to picture it: think of iron like a magnet for oxygen. It grabs oxygen in your lungs and carries it to every tissue in your body - your brain, your muscles, your skin, your hair follicles. All of it needs oxygen delivered, and iron is doing the delivering.
Here's the “wow” fact I like to share with patients: your red blood cells only live about 120 days. That's about four months. Your body is constantly breaking down old red blood cells and building brand-new ones - every single day, month after month, for your entire life.
And every one of those new red blood cells needs iron to be built correctly.
So think about what that means if you're a woman who's still cycling. Every month, you're losing blood - and your body is already on a four-month rebuild cycle for red blood cells even without that monthly loss. Add regular blood loss on top of a process that already demands a constant iron supply, and you start to see why this becomes such a common issue for women.
So when I think about iron, I'm not just thinking about one lab number. I'm thinking about a factory that never stops running - and iron is one of the raw materials that factory needs to keep producing.
Iron has a few jobs, but three matter most.
Red blood cell formation. Your body is building new red blood cells constantly, and iron is a non-negotiable ingredient in that process. I like to tell patients: think of iron and B12 as two of the key ingredients your body needs to build a red blood cell. Iron builds the part that carries oxygen. B12 helps the cell actually form and mature correctly. Miss either ingredient, and the recipe doesn't work.
Oxygen transport. Once red blood cells are built, iron is what actually grabs onto oxygen in your lungs and carries it to the rest of your body. Without enough of it, your tissues are essentially running short on fuel.
Energy production. Think of your cells' energy-making process like a relay race, with oxygen being passed from runner to runner until it reaches the finish line - tiny structures inside your cells called mitochondria, where energy actually gets made. Iron is the runner carrying that final leg.
So when someone tells me they're exhausted, foggy, and just not themselves - iron is always somewhere on my list of questions to ask.
I want you to picture a patient I'll call Sarah. Late 40s. Busy. And then, seemingly out of nowhere, her periods change - she's bleeding through her pants in the middle of the day at 45, something that never happened to her in her 20s or 30s. What used to be predictable now shows up heavier, longer, and closer together than it used to.
If that description sounds familiar, I want you to keep listening.
The people most likely to run low on iron include women with heavy menstrual bleeding, women who are pregnant, anyone who donates blood regularly, people with GI conditions that affect absorption such as celiac disease or an H. pylori infection, anyone who's had bariatric surgery, and people eating a vegan or vegetarian diet.
And here's one that surprises people: the bacteria living in your gut actually compete with you for iron. Most of the iron you eat doesn't even make it to your bloodstream - your gut bacteria use it first. So if your gut microbiome is out of balance, something like small intestinal bacterial overgrowth, or SIBO, those bacteria can be quietly eating up the iron before your body ever gets the chance.
This is exactly why, when iron stays stubbornly low despite supplementing, I often want to look deeper at gut health instead of just increasing the dose.
Sarah checks two or three of those boxes without even trying. A lot of women do - and that's exactly why this conversation matters so much for this stage of life.
Your symptoms are data. They're not random - they're clues your body is leaving for you.
When iron runs low, women commonly notice fatigue that doesn't improve with sleep, hair loss, brain fog, restless legs, and exercise intolerance.
How many women have been told their fatigue is “just hormones,” without anyone ever checking whether they're also becoming iron deficient?
I ask that question a lot, because in my experience, it's often both.
This is the part of the episode I think is genuinely the most useful, so let's slow down here.
At its core, anemia means your body doesn't have enough oxygen getting where it needs to go because you don't have enough oxygen-carrying red blood cells to do the job. There are different types of anemia with different underlying causes. Iron deficiency is just one of them, but it's one of the most common.
Most people have only ever had a CBC - a complete blood count. That test can tell you if you're anemic. What it often doesn't tell you is whether your iron stores are running low, which can happen well before anemia shows up.
To really understand your iron status, there are a few pieces to look at together:
Ferritin - this measures your iron stores.
Serum iron - this measures the iron actually circulating in your blood right now.
TIBC, or total iron-binding capacity - this tells us how much your blood is “reaching” for iron.
Transferrin saturation - this shows what percentage of your iron-carrying protein is actually full.
No single one of these tells the whole story. They're like different instruments on a weather station - wind speed alone doesn't tell you if a storm is coming. You need the whole picture.
Conventional medicine isn't wrong here - reference ranges are built to identify disease, and they're good at that job. But functional medicine asks an additional question: is this level optimal for this person's physiology, symptoms, and stage of life?
Here's a real pattern I see often: a woman comes in with a completely normal CBC. Normal serum iron. But her ferritin is sitting at 12 - technically “in range” on many lab reports - and she has hair loss, fatigue, and brain fog.
Technically normal. Practically, her body is telling a different story.
I also want to mention the flip side: ferritin can rise during inflammation, even when iron stores aren't actually elevated. So a high ferritin doesn't automatically mean iron overload. This is exactly why we don't look at one number in isolation.
Think of ferritin like a savings account, and serum iron like your checking account.
Your checking account - serum iron - is what you're using day to day. Your savings account - ferritin - is your reserve. You can have money in checking and still have an empty savings account.
That's what's happening with a lot of women. Their day-to-day iron looks fine, but their reserves - their ferritin - have been slowly drained by years of heavy periods, and nobody ever checked the account balance until the symptoms showed up.
Most standard labs will call anything above roughly 12 to 15 “normal.” But in my experience, and in a lot of the functional medicine literature, symptoms like fatigue, hair loss, and brain fog often show up well before that - and most practitioners in this space are looking for a savings account balance closer to 50 to 100, not just “above the bottom of the range.”
I'm not going to hand you one rigid “ideal” number for you, because that number depends on you - your symptoms, your history, your stage of life. We treat the patient, not just the lab value.
If you and your provider determine that supplementing is the right move, how you do it matters just as much as whether you do it.
Let's start with food, because that's always the foundation. Iron from animal sources - think red meat, chicken, turkey, salmon, shrimp, and eggs - is absorbed far more efficiently than iron from plant sources like spinach or lentils. Pairing plant sources with vitamin C can meaningfully improve absorption.
Cooking in a cast iron pan really can transfer small amounts of iron into your food, especially with moist, acidic dishes like tomato sauce or applesauce. But it's a gentle assist, not a treatment. If your ferritin is actually low, a cast iron skillet isn't going to fix that on its own.
Common supplemental forms include heme iron, ferrous bisglycinate, ferrous sulfate, and liquid or chewable options.
This is not a “more is always better” nutrient. Iron supplementation should be intentional, not automatic.
I want to spend real time here, because this is the single biggest reason people quit their iron supplement.
Iron can be irritating to the GI tract. When it's not fully absorbed, the unabsorbed portion continues through your intestines, where it can change stool consistency and affect gut motility.
The good news is there's almost always a workaround: switching formulations, staying well hydrated, making sure fiber intake is adequate, considering magnesium, and sometimes dividing the dose.
If iron has made you miserable in the past, please don't assume that means iron just “isn't for you.” It often means the form or the strategy needs to change.
Iron deficiency gets most of the attention, but it isn't the only concern.
Before starting or continuing long-term supplementation, it's worth reviewing your multivitamin, any prenatal you're taking, and your family history. Hereditary hemochromatosis - a genetic condition that causes the body to absorb too much iron - is more common than most people realize.
If your ferritin comes back high, the first step isn't panic - it's a full workup. Sometimes high ferritin really is genetic hemochromatosis. Sometimes it's from taking in more iron than your body needs. And sometimes it may reflect another process entirely.
If it does turn out to be true hereditary hemochromatosis, treatment is usually therapeutic phlebotomy - having blood drawn on a regular schedule to bring iron levels back down.
More is not always better. That's true for iron just like it's true for almost everything else we talk about on this podcast.
A few things I've learned in practice:
I don't automatically recommend iron just because someone is tired. Fatigue has a long list of possible causes, and iron is one piece of a bigger picture.
My biggest pet peeve is when someone is told their iron is “fine” based on a CBC alone, without ever looking at ferritin.
The most common mistake I see patients make is stopping their iron the moment it upsets their stomach, instead of switching forms first.
One pattern I've seen clinically, and I'll say clearly this is an observation from my own practice, not a hard rule: in patients with low iron, when we support methylation - meaning B12 and folate status - I've often seen their serum iron respond and improve alongside it.
And one of my favorite patterns to catch clinically is a normal CBC sitting right next to a ferritin that's telling a completely different story.
Before we wrap up, I want to leave you with a few questions you can bring to your own healthcare provider.
Have we looked at my full iron panel - ferritin, serum iron, and TIBC - or just a CBC?
Could my heavier or longer periods be contributing to low iron?
Is my ferritin actually appropriate for my symptoms, not just technically in range?
Do we know why my iron is low, or are we just replacing it?
Should we rule anything else out before I start supplementing long-term?
So here's what I want you to take away from today.
Iron deficiency isn't a diagnosis - it's a clue.
Iron wasn't what saved my patient's life. Asking why he was iron deficient is what led to the diagnosis. And that's exactly why I say iron isn't just another lab - sometimes, it's the lab that could save your life.
Before you simply replace what's low, get curious about why it's low in the first place. That question is the difference between chasing a number and actually understanding your body.
If you're curious what your own iron story might be, functional testing can often help fill in the gaps your CBC alone can't show you.
Thanks for spending this time with me today. Until next time, I'm Dr. Emily Wheeler - and remember, your body is talking. Let's keep listening.
Dr. Emily Wheeler
Dr. Emily Wheeler is a functional medicine practitioner, speaker, educator, and host of the Rise Above podcast. With nearly 20 years of clinical experience, she helps women uncover the root causes of chronic symptoms through personalized, science-based care. Her mission is to help women understand their bodies, restore their vibrance, and rise above the gaps in healthcare.
Learn how Dr. Emily currently works with patients and where to begin.