You can have an iron deficiency while your haemoglobin is still normal. Your ferritin, the iron store, is then already low, but you are not yet anaemic. Many women feel tired in this phase, while a standard blood test looks normal.
I notice this is one of the most often missed causes of tiredness. The GP sometimes only looks at haemoglobin, and that can be fine while your store is nearly empty. Below you read why that works this way and when a ferritin measurement is useful.
The difference between iron deficiency and anaemia
Iron deficiency and anaemia are not the same. An iron deficiency starts with a falling store (ferritin). Only when that store is truly empty does your haemoglobin drop and do you speak of iron-deficiency anaemia. There is often a long phase in between.
Your body protects your haemoglobin as long as possible. It first takes iron from the store before the production of red blood cells suffers. So you can have a low ferritin with a normal haemoglobin for months, and still feel complaints in that time.
Which complaints fit a low ferritin?
A low ferritin often gives vague complaints that you do not immediately link to iron. Tiredness comes first, but there are more signals that together form a pattern.
- Persistent fatigue, even after enough sleep
- Quickly out of breath or a pounding heart on exertion
- Hair loss or brittle nails
- Concentration problems or a foggy feeling in your head
- Restless legs, especially in the evening
These complaints also fit other causes, like an underactive thyroid or a vitamin shortage. So a symptom alone says little. Also read our overview on which blood values to test for fatigue.
Why a normal haemoglobin does not reassure you
If only your haemoglobin is measured, a low ferritin can go unnoticed. You then hear that your blood is fine, while your store is nearly empty. That explains why some women keep feeling tired despite a normal result.
So with unexplained tiredness it is useful to include the ferritin. A lowered ferritin with a normal haemoglobin can be a lead that is otherwise missed. Always discuss a low result with your GP.
What exactly do you test?
For a complete picture you look at your store and at the iron in your blood. Together they show whether you have a deficiency and how far it has progressed.
- Ferritin is the iron store and falls first.
- Iron (serum) shows how much iron is in your blood at that moment.
- Transferrin is the transport protein and often rises when your store is low.
- Haemoglobin shows whether anaemia is already present.
The Iron Status measures these values in one draw, so you know not only whether you have a deficiency, but also which phase. Want to know how to keep your iron up? Read our article on preventing iron deficiency with nutrition and supplements.
When is testing worthwhile?
A ferritin measurement is mainly useful with unexplained tiredness, especially if you lose or need extra iron. Women are at higher risk through menstruation, pregnancy and breastfeeding.
Consider a ferritin measurement if you recognise this:
- You are persistently tired while an earlier result was normal
- You have heavy or long periods
- You have been pregnant or are breastfeeding
- You eat little or no meat
At Lunara you test without a referral and your result gets context per value from a BIG-registered doctor. You do not simply supplement a low ferritin yourself: too much iron is not desirable either, so discuss supplementation with your GP.
Frequently asked questions
Can ferritin be too low with a normal Hb?
Yes. Your store (ferritin) falls before your haemoglobin suffers. So you can have a low ferritin with a normal haemoglobin, and still feel complaints.
Which ferritin value is too low?
That depends on the laboratory and your situation. A value at the bottom of or just below the reference range can already cause complaints, especially in women. So read your result together with a doctor.
Should I take iron tablets straight away?
Not without consultation. Too much iron can be harmful, and the cause of the deficiency also deserves attention. Discuss supplementation and the right dose with your GP.
References
- Verdon F, Burnand B, Stubi CL, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ. 2003;326(7399):1124.
- NHG-Standaard Anemie. Dutch College of General Practitioners. Available via nhg.org.
- NHG and Thuisarts.nl. Iron-deficiency anaemia. Dutch College of General Practitioners. Available via thuisarts.nl.
Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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