Ferritin seems to be having a moment.
I’m seeing more conversations about low ferritin in women, particularly women who have been feeling tired for months or even years despite being told that their blood tests are “normal”.
I’m glad we’re talking about it!
Iron deficiency can exist before someone becomes anaemic, which means haemoglobin may still be within range while iron stores are becoming depleted.
But there’s another part of the conversation that I think is just as important.
If your ferritin is low, the question shouldn’t only be: “How much iron should I take?”
It should also be:
“Why is my ferritin low in the first place?”
What does ferritin actually tell us?
Ferritin is a protein that stores iron, and measuring it gives us a useful indication of the body’s iron reserves.
When those stores start running low, you may experience symptoms even before your haemoglobin falls enough to be classified as anaemia.
Persistent fatigue is probably the symptom people associate most with iron deficiency, but breathlessness, reduced exercise tolerance, difficulty concentrating, restless legs and changes to hair such as hair loss and nails can also occur.
The difficulty is that these symptoms aren’t specific to iron deficiency. Feeling exhausted doesn’t automatically mean your ferritin is low, which is why testing matters.
A “normal” haemoglobin doesn’t tell us everything
Haemoglobin and ferritin tell us different things. Haemoglobin tells us about the oxygen-carrying protein in our red blood cells. Ferritin gives us information about stored iron.
Your body can therefore be drawing down its iron reserves while still maintaining haemoglobin within the laboratory range.
Eventually, if iron depletion continues, iron-deficiency anaemia may develop. But we don’t necessarily need to wait until someone becomes anaemic before recognising that their iron stores are low.
So what counts as low ferritin?
This is where things get interesting.
In September 2026, the American Society of Hematology published new guidelines recommending a ferritin threshold of 30 µg/L or below for diagnosing iron deficiency in menstruating people and other adults. For menstruating people with heavy menstrual bleeding, symptoms or other risk factors, a threshold of 50 µg/L may sometimes be appropriate.
Here in the Netherlands, however, women may still see a ferritin of 20 µg/L sitting at the bottom of a laboratory reference range. In the UK there isn’t even one consistent lower limit, with ranges varying between laboratories.
This highlights an important distinction between a laboratory reference range and a clinical threshold used to diagnose iron deficiency.
So when a woman is told that her ferritin is “normal”, I think it’s reasonable to ask what the actual number is rather than stopping at the word normal.
At the same time, I don’t think we should simply replace one arbitrary number with another and decide that every woman needs a ferritin above 50, 70 or 100.
Ferritin needs to be interpreted alongside symptoms, menstrual history, haemoglobin and red blood cell markers and, when appropriate, other iron studies.
I’d also want to understand why iron stores are low in the first place. Are periods particularly heavy? Is there enough iron coming from the diet? Could absorption be an issue? And if there are other symptoms such as feeling cold, hair changes or persistent fatigue, has thyroid function been considered too?
There’s another complication. Ferritin can rise during inflammation, so an apparently reasonable ferritin result doesn’t always rule out iron deficiency.
The number matters. The context matters just as much.
Why did your iron stores become depleted?
For menstruating women, blood loss is one of the most obvious places to start.
Heavy or prolonged periods can gradually drain iron stores month after month. This can become particularly relevant during perimenopause, when some women experience heavier or more unpredictable bleeding. And heavy periods themselves deserve attention. Continually replacing iron without addressing significant ongoing blood loss may only solve part of the problem.
Diet matters too.
Iron is found in both animal and plant foods, although we absorb these forms differently. Someone eating very little iron-rich food may simply not be getting enough to replace what they lose.
If ferritin remains low despite taking iron appropriately, or repeatedly drops again, that deserves further investigation. Sometimes absorption is part of the picture. Coeliac disease, for example, is a recognised cause of iron deficiency, and certain gastrointestinal conditions and medications can also affect iron status.
This doesn’t mean every woman with low ferritin needs extensive investigations. It means persistent or recurrent iron deficiency deserves attention.
Taking iron is only one part of the picture
Iron supplements can be extremely useful when they’re needed. But I don’t think we should replace one problem – women being told their low iron doesn’t matter – with another one where everyone is encouraged to take high-dose iron based on a single ferritin number.
If your iron stores are low, the aim should be to replenish them appropriately, monitor the response and, importantly, understand what caused them to become depleted.
Sometimes the explanation is relatively straightforward: heavy periods combined with inadequate dietary iron. Sometimes there is more to investigate. And sometimes fatigue isn’t being caused by iron deficiency at all.
When I look at iron status with a client, I’m not interested in ferritin alone. I want to understand the wider picture – their history, blood results, periods, diet, digestive health, thyroid health, previous iron deficiency, and the symptoms they’re actually experiencing.
Because a ferritin result is useful.
But understanding why it is low is much more useful.
So if you’ve repeatedly been told that your blood tests are “normal” but you’re struggling with persistent fatigue, it may be worth looking back at whether your iron stores were actually assessed – not just whether you were anaemic.
And if your ferritin is low, don’t stop at the number.
Let’s find out why.