Low Iron: A Root-Cause Approach to Treatment
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Iron supplements that do nothing more than make you constipated.
Doctor telling you your iron levels all check out, but you're still symptomatic.
No matter what you do - nothing improves and "low iron" has just become your (not so normal) normal.
Sound familiar?
Recurrent iron deficiency is a finding. The important clinical work is understanding why iron is being lost, poorly absorbed or not able to be used by the body. This is deeper than just finding the perfect supplement and eating more red meat & vitamin C.
What is iron deficiency?
Iron is best known for its role in haemoglobin and oxygen transport, but it is also involved in mitochondrial energy metabolism and multiple enzyme systems. Iron stores may become depleted before haemoglobin falls below the laboratory reference range.
This is why a person can have iron deficiency without anaemia and still report fatigue, reduced exercise tolerance, headaches, impaired concentration or hair shedding. A normal haemoglobin result does not automatically mean iron status is adequate.
Ferritin is useful — but it is not the whole iron picture.
Ferritin is the major intracellular iron-storage protein and serum ferritin is widely used as a marker of iron stores. A clearly low ferritin concentration strongly supports iron deficiency.
However, ferritin is also an acute-phase reactant. Inflammation can raise ferritin, sometimes obscuring depleted iron availability. In inflammatory states, ferritin should be interpreted alongside the clinical picture and other markers such as transferrin saturation.
Serum iron, by contrast, is variable and is not a reliable stand-alone marker of iron status. The value lies in interpreting the full pattern.
Where transferrin comes in
Ferritin tells us about stores. Transferrin tells us about transport, and reading the two together is where a lot of the useful clinical information sits.
Transferrin is the protein that carries iron through the bloodstream to where it's needed - bone marrow, muscle, every iron-dependent enzyme system in the body. When the body senses that stores are running low, the liver typically increases transferrin production, in an attempt to maximise the capture of whatever iron is available. This is why, in straightforward iron deficiency, we often see a pattern of low ferritin alongside a rising transferrin (or total iron-binding capacity, TIBC) and a falling transferrin saturation - the body is producing more "delivery vehicles" because there isn't enough iron to go around.
This is a genuinely useful correlation. If ferritin is low and transferrin is elevated with a low saturation percentage, that combination is far more convincing evidence of true iron deficiency than ferritin in isolation. It's also part of why I don't rely on a single number to make a clinical decision - the relationship between the markers carries more information than either one alone.
Where it gets more interesting is when that expected inverse relationship doesn't hold. If ferritin looks "normal" or even elevated, but transferrin and transferrin saturation are also low, that pattern doesn't fit tidy iron deficiency - it starts to look like something else is influencing the picture, which brings us to inflammation.
When iron markers reflect something else going on
Iron studies don't exist in isolation from the rest of the body's physiology, and this is a piece that gets missed when results are read number-by-number rather than as a pattern.
Inflammation, infection and chronic illness all activate a hormone called hepcidin, produced mainly by the liver. Hepcidin's job, in simple terms, is to lock iron away - it reduces iron absorption from the gut and traps iron inside storage cells (raising ferritin) rather than allowing it to circulate freely (which is reflected in a falling serum iron and transferrin saturation). This is sometimes called the anaemia of inflammation or anaemia of chronic disease, and it can look quite different to straightforward iron-deficiency anaemia, even though a person may feel just as fatigued.
This matters clinically because ferritin can sit within, or even above, the reference range while functional iron availability is actually poor. If I see a ferritin that "looks fine" in someone with ongoing symptoms, a recent or current infection, gut symptoms suggestive of dysbiosis or pathogenic overgrowth, or a known inflammatory condition, I want to look at transferrin saturation and inflammatory markers such as CRP before assuming iron status is adequate. A high-normal ferritin sitting alongside a low transferrin saturation and an elevated CRP tells a very different story to a high-normal ferritin with a normal transferrin saturation and no inflammatory signal.
Pathogens themselves also compete for iron - many bacteria and some parasites need it to replicate, which is part of why the body's own response to infection is to withhold it. It's a useful reminder that iron studies are also, in part, a window into what else might be going on immunologically or in the gut, not purely a nutrition panel.
Why we don't want to iron-load when the body is fighting infection
This is where the physiology above becomes practically important. The hepcidin-driven "iron withholding" response during infection or active inflammation isn't a glitch - it appears to be a protective mechanism, sometimes referred to as nutritional immunity. By reducing circulating free iron, the body makes it harder for many pathogens to access the iron they need to multiply.
Pushing iron supplementation, particularly higher-dose oral iron, into this window doesn't just risk being ineffective because absorption is already down-regulated - there's also a reasonable body of evidence and mechanistic concern that supplying additional iron during active infection may not be helpful, and in some contexts may favour certain pathogens or worsen gut dysbiosis, since unabsorbed iron in the gut is also available to less favourable bacteria.
In practice, this means timing matters. If someone is acutely unwell, has an active infection, or has clear inflammatory markers, my priority is usually to address that first, rather than layering iron on top of an inflammatory state where it's unlikely to be well utilised and may not be the safest thing to be doing. Once the acute picture has settled, iron status can be reassessed properly, without inflammation muddying the interpretation.
What I look for in comprehensive iron studies...
Depending on the clinical context, I may review ferritin, serum iron, transferrin or total iron-binding capacity, transferrin saturation, haemoglobin, haematocrit, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), red cell distribution width (RDW) and inflammatory markers such as C-reactive protein.
The goal is not to chase isolated numbers. It is to ask whether the pattern suggests depleted stores, emerging microcytosis, reduced haemoglobinisation of red cells, inflammation-related iron restriction or another haematological issue that requires medical assessment.
Patterns that make me look more closely →
Some findings or trends warrant closer investigation rather than automatic repeat supplementation:
- falling haemoglobin or a progressive downward trend
- low MCV or MCH, suggesting a microcytic or hypochromic pattern
- rising RDW alongside falling iron stores
- low transferrin saturation
- ferritin that appears adequate in the context of inflammation
- failure to respond as expected to appropriately taken oral iron
- heavy or unexplained bleeding
- gastrointestinal symptoms or blood in the stool
Why does iron keep dropping?
Recurrent deficiency usually makes me consider three broad mechanisms: ongoing loss, impaired absorption or requirements that exceed intake.
In menstruating women, heavy menstrual bleeding is a major contributor. I want to know whether bleeding is prolonged, whether there is flooding through clothes or bedding, how often menstrual products are changed, and whether large clots are passed. Heavy menstrual bleeding may itself warrant gynaecological investigation.
Gastrointestinal blood loss also matters. Visible blood in the stool, persistent bowel changes, unexplained weight loss or recurrent iron deficiency should not be managed indefinitely with supplements alone.
Absorption can be affected by coeliac disease, inflammatory bowel disease and previous gastrointestinal surgery. Pregnancy, postpartum depletion and frequent blood donation can also increase the risk of deficiency.
Food matters, but food is not always the root cause - or solution.
Haem iron from meat and seafood is generally more bioavailable than non-haem iron from plant foods. Useful non-haem sources include legumes, tofu, tahini, pumpkin seeds, leafy green vegetables and iron-fortified foods.
Pairing plant-based iron with vitamin C-rich foods can enhance non-haem iron absorption. Coffee and tea consumed with iron-rich meals may reduce non-haem iron absorption, so timing can matter when someone is actively correcting deficiency.
However, telling a woman with heavy menstrual bleeding to "eat more steak" misses the clinical issue if she is losing iron faster than she can replace it.
A note on iron supplements
Oral iron can be effective, but form, dose, frequency, tolerance and duration matter. Research into hepcidin physiology has also challenged the assumption that more frequent dosing always improves absorption.
Supplementation should be individualised. Persistent intolerance, poor response or significant anaemia may require medical review and, in some circumstances, intravenous iron.
Oral iron or an infusion? And what else needs to be considered
Not everyone needs an infusion, and not everyone should go straight to one. But there are situations where I'll actively raise it as a conversation to have with a GP or specialist, rather than continuing to push oral supplementation:
- iron deficiency is severe or symptomatic, and correction needs to happen faster than oral repletion allows
- ongoing losses (such as heavy menstrual bleeding) are outpacing what oral iron can realistically replace
- malabsorption is present or suspected - coeliac disease, inflammatory bowel disease, previous bariatric or gastrointestinal surgery
- oral iron has been trialled properly - appropriate form, dose and duration - and either isn't being tolerated or isn't shifting the numbers
- there's a time-limited window, such as later pregnancy or pre-surgical optimisation, where oral correction isn't realistic
An infusion isn't just a faster way to do the same thing as a tablet, though, and there are a few things worth having factored in before one goes ahead:
Inflammation and infection status matter here too. Given what hepcidin does to iron handling, infusing iron into an active inflammatory or infective state can mean the iron is taken up into storage rather than being available for the body to actually use, which somewhat defeats the purpose. Where possible, it's worth having infection and significant inflammation reasonably settled, or at least accounted for, before proceeding.
It's also worth medically excluding other causes of an unusual iron picture - such as haemochromatosis or other causes of iron overload - before adding a large iron load intravenously, and making sure the reason for ongoing deficiency (heavy bleeding, GI losses, malabsorption) is being investigated or managed in parallel, rather than only topping up the tank.
Infusions are done in a medical setting because of the (uncommon but real) risk of infusion reactions, so this isn't something to source or administer outside appropriate medical care. Follow-up is also part of the process - ferritin can climb quite high immediately post-infusion and needs to be interpreted with that in mind, and repeat testing a few months later gives a truer picture of where iron status has settled.
When naturopathic support may be helpful...
Naturopathic support may be appropriate when ferritin repeatedly falls, iron supplements cause gastrointestinal side effects, symptoms continue despite apparently "normal" blood results, heavy periods are present, or digestive symptoms suggest a possible absorption issue.
A naturopath can review your pathology longitudinally, assess dietary intake and menstrual or gastrointestinal clues, and coordinate referral when the pattern warrants medical investigation.
The aim is not to keep topping up a leaking bucket. It is to find the leak.
Let's look deeper.
At Whole Self Naturopathy, I look beyond isolated symptoms and consider the whole picture — your health history, pathology, nutrition, lifestyle and the patterns connecting how you feel. My approach is evidence-based, practical and designed to make your health feel uncomplicated and actually achievable, with collaborative medical care or referral recommended where appropriate.
Book a naturopathic consultation today.
References
Auerbach, M., DeLoughery, T. G., & Tirnauer, J. S. (2025). Iron deficiency in adults: A review. JAMA, 333(20), 1813–1824.
Ganz, T. (2019). Anemia of inflammation. New England Journal of Medicine, 381(12), 1148–1157.
Munro, M. G., Mast, A. E., Powers, J. M., Kouides, P. A., O'Brien, S. H., Richards, T., Lavin, M., & Breymann, C. (2023). The relationship between heavy menstrual bleeding, iron deficiency, and iron deficiency anemia. American Journal of Obstetrics & Gynecology, 229(1), 1–9.
Nairz, M., & Weiss, G. (2020). Iron in infection and immunity. Molecular Aspects of Medicine, 75, 100864.
Stoffel, N. U., Cercamondi, C. I., Brittenham, G., Zeder, C., Geurts-Moespot, A. J., Swinkels, D. W., Moretti, D., & Zimmermann, M. B. (2017). Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: Two open-label, randomised controlled trials. The Lancet Haematology, 4(11), e524–e533.