If you’ve had blood tests showing low ferritin, you may have simply been told to take an iron supplement.
And while replacing iron can absolutely be important, there’s another question that’s equally worth asking:
Why are your iron stores low in the first place?
Low ferritin isn’t always simply a sign that you need to eat more iron.
You might not be consuming enough. But you could also be losing more iron than you’re able to replace, struggling to absorb it properly, or have increased requirements. Certain health conditions and medications can also interfere with iron absorption or the way iron is handled by the body.
This is particularly worth thinking about for women during perimenopause, when changes to menstrual bleeding can make iron deficiency more likely.
So let’s look at some of the potential reasons your ferritin might be low, and why simply taking more iron doesn’t always address the whole picture.
First, what is ferritin?
Ferritin is a protein that stores iron within the body, and measuring ferritin in the blood gives us useful information about our iron reserves.
Iron itself is essential for numerous processes, including the production of haemoglobin, the protein in red blood cells responsible for transporting oxygen around the body.
Importantly, your iron stores can start becoming depleted before you develop iron-deficiency anaemia.
This means it’s possible to have haemoglobin within the laboratory reference range while your ferritin is already low.
For some people, depleted iron stores may be associated with symptoms such as fatigue, reduced exercise tolerance, weakness, difficulty concentrating, restless legs or hair shedding.
So if ferritin is low, replenishing those stores may be important.
But I also want to understand why they’ve become depleted.
1. Heavy periods
For menstruating women, one of the most important potential causes of low iron stores is menstrual blood loss.
Every period involves some loss of iron. When periods become particularly heavy, prolonged or frequent, iron losses can begin to exceed the amount you’re able to replace through your diet.
This is particularly relevant during perimenopause.
Although we often think of periods simply becoming less frequent before eventually stopping, the transition towards menopause can be much more unpredictable.
Some women experience periods that become:
- Heavier
- Longer
- More frequent
- More erratic
- Associated with flooding or large clots
Repeated heavy menstrual bleeding can gradually deplete iron stores and eventually contribute to iron-deficiency anaemia.
If heavy periods are contributing to low ferritin, replacing iron is only one part of the picture. It’s also important to investigate and appropriately manage the reason for the excessive bleeding. You can read my previous blog post on reasons why your periods moght be heavy in perimenopause here.
2. Not eating enough iron
Sometimes low iron stores really can come down to inadequate dietary intake.
Dietary iron exists in two main forms.
Haem iron is found in animal foods, particularly meat, and is generally more readily absorbed by the body.
Non-haem iron is found in plant foods including beans, lentils, tofu, nuts, seeds, whole grains and leafy green vegetables.
A well-planned vegetarian or vegan diet can provide plenty of iron, but because non-haem iron is generally less readily absorbed, people eating predominantly plant-based diets may need to pay particular attention to getting enough.
Low overall food intake, restrictive diets or simply not regularly eating iron-rich foods can also contribute to depleted stores.
But dietary intake is only one part of the equation.
3. Poor iron absorption
You can eat an iron-rich diet, and even take an iron supplement, but the iron still needs to be absorbed through your digestive system.
Iron is predominantly absorbed in the upper small intestine, and certain gastrointestinal conditions can interfere with this process.
This becomes particularly important when someone’s diet appears to contain plenty of iron, yet their ferritin remains persistently low.
Rather than continually increasing iron intake, it may be worth asking:
Is the body actually absorbing it?
4. Coeliac disease
Coeliac disease damages the lining of the small intestine and can interfere with nutrient absorption, including iron.
In fact, unexplained iron deficiency can sometimes be one of the signs that leads to coeliac disease being identified, even in someone who doesn’t have the digestive symptoms they might typically associate with the condition.
Persistent low ferritin that isn’t responding as expected to iron supplementation therefore deserves further investigation rather than simply assuming more iron is required.
5. H. pylori infection
Helicobacter pylori (H. pylori) is a bacterium that can colonise the stomach and is perhaps best known for its association with gastritis and stomach ulcers.
However, H. pylori infection has also been associated with iron deficiency.
Several mechanisms may be involved, including changes to the stomach environment that can interfere with iron absorption.
This doesn’t mean everyone with low ferritin needs to be tested for H. pylori. But it may be something to consider in cases of otherwise unexplained or persistent iron deficiency, particularly alongside relevant gastrointestinal symptoms.
6. Inflammatory bowel disease and other digestive conditions
Inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis can also contribute to iron deficiency.
There may be several things happening simultaneously, including:
- Gastrointestinal blood loss
- Reduced dietary intake
- Impaired iron absorption
- Chronic inflammation affecting the way iron is handled by the body
Previous gastrointestinal surgery can affect nutrient absorption too.
For example, people who have undergone certain forms of bariatric surgery may be at increased risk of iron deficiency and require ongoing monitoring.
7. Certain medications
Medication history can sometimes provide another piece of the puzzle.
Long-term use of proton pump inhibitors (PPIs), which reduce stomach acid production, has been associated with impaired iron absorption in some people.
That doesn’t mean you should stop prescribed medication if you discover your ferritin is low. Medication should always be reviewed with the healthcare professional responsible for prescribing it.
But if iron stores remain persistently low, it’s useful to consider whether medication could be contributing.
Other medications, including regular use of certain anti-inflammatory drugs such as NSAIDs, may potentially contribute to gastrointestinal bleeding in some individuals.
8. Blood loss from somewhere other than your period
Menstrual bleeding isn’t the only possible source of iron loss.
Slow, ongoing blood loss from the gastrointestinal tract can gradually deplete iron stores, and it isn’t necessarily something you would visibly notice.
This is particularly important when iron deficiency occurs in men or postmenopausal women, where there isn’t the regular iron loss associated with menstruation.
Unexplained or recurrent iron deficiency should therefore be appropriately investigated rather than automatically attributed to diet.
Other circumstances that can contribute to iron loss include frequent blood donation, surgery, injury and blood loss during childbirth.
9. Increased iron requirements
There are also times in life when the body simply requires more iron.
Pregnancy substantially increases iron requirements because iron is needed to support increased maternal blood volume and the developing baby.
Adolescence and periods of rapid growth also increase requirements.
Looking at someone’s wider history can therefore be helpful.
Pregnancy, childbirth, the return of menstruation and then increasingly heavy perimenopausal periods can potentially create a long period during which iron requirements and losses are relatively high.
10. Things that interfere with iron absorption
Sometimes smaller dietary habits can make a difference too, particularly when iron intake or stores are already relatively low.
Tea and coffee contain polyphenols that can inhibit the absorption of non-haem iron when consumed alongside an iron-containing meal or supplement.
Calcium can also temporarily reduce iron absorption when consumed at the same time.
This doesn’t mean you need to avoid tea, coffee or calcium-containing foods.
Instead, if you’re actively trying to replenish depleted iron stores, it may be helpful to think about timing them separately from your iron supplement.
Vitamin C can enhance the absorption of non-haem iron, so combining plant sources of iron with vitamin-C-rich foods can be useful.
What about chronic inflammation?
Inflammation deserves its own mention because it can make iron results a little more complicated to interpret.
Chronic inflammation doesn’t necessarily make ferritin lower.
In fact, it can make ferritin higher.
Ferritin is what’s known as an acute-phase protein, which means levels can rise in response to inflammation.
Inflammation can also increase production of hepcidin, a hormone involved in regulating iron.
Higher hepcidin levels reduce the amount of iron absorbed through the intestine and encourage the body to retain iron within storage cells, meaning less iron is available for use.
This can contribute to what’s sometimes described as functional iron deficiency.
As a result, someone experiencing inflammation could potentially have impaired iron availability while their ferritin appears relatively normal, or even elevated.
This is one of the reasons ferritin shouldn’t always be interpreted completely in isolation.
Depending on the individual circumstances, healthcare practitioners may also consider markers such as haemoglobin, MCV, MCH, transferrin saturation and inflammatory markers such as CRP, alongside symptoms and medical history.
What if you’re taking iron but your ferritin isn’t increasing?
If you’ve been taking an appropriate iron supplement and your ferritin remains persistently low, I’d want to come back to the underlying question:
Why?
Are you continuing to lose significant amounts of blood through heavy periods?
Are you taking your supplement alongside something that could reduce its absorption?
Are you getting enough iron through your diet?
Could there be a gastrointestinal condition affecting absorption?
Could medication be playing a role?
Is there another source of blood loss?
Or is there something else that needs investigating?
Simply continuing to increase the amount of iron you’re taking isn’t necessarily the solution.
Low ferritin is a clue but it’s not the whole story
If there’s one thing I’d like you to take away from this article, it’s this:
Low ferritin is a finding. The next question is why.
Sometimes the explanation is relatively straightforward.
If you’ve developed very heavy periods during perimenopause and your ferritin has gradually fallen alongside them, there may be a fairly obvious connection.
But if the explanation isn’t clear, or your levels aren’t improving despite supplementation, that’s when it’s particularly important to investigate further.
Rather than only asking:
“What iron supplement should I take?”
I’d encourage you to also ask:
“Why have my iron stores become depleted in the first place?”
Because understanding the reason gives you a much better chance of addressing the problem properly, rather than continually trying to replace what you’re losing.
Want to learn more?
I explore this topic in more detail in this week’s episode of the Empowered Perimenopause Podcast: Why Is My Ferritin Low? The Reasons Your Iron Stores Might Be Depleted.
Listen to the episode (episode 100) here.
And if you’re navigating perimenopause and would love somewhere to learn, ask questions and feel supported along the way, you can also find out more about Midlife Thrive, my online perimenopause community, here.
This article is for educational purposes only and is not intended to diagnose or treat a medical condition. Unexplained iron deficiency, persistent low ferritin, iron-deficiency anaemia or abnormal bleeding should be discussed with an appropriate healthcare professional.
