You are tired, your hair is shedding more than usual, and your GP told you your blood was "fine." Yet you still feel off. Often the answer is not in the one number that was checked, but in the value that was never ordered: your ferritin. A normal haemoglobin does not rule out iron deficiency, and that is exactly where many people get stuck.
My position: testing haemoglobin alone is too blunt for vague fatigue complaints. Haemoglobin only drops once your stores have been empty for months. If you want to catch a deficiency early, you look at the whole iron chain.
Which values does an iron panel measure?
A reliable iron profile uses several values that complement each other. A single number can mislead, especially when inflammation is present.
| Blood value | What it measures | Points to deficiency when |
|---|---|---|
| Ferritin | Your iron stores | Low (often below 30 ug/L) |
| Haemoglobin | Oxygen transport in red cells | Low, but only at a later stage |
| MCV | Size of your red blood cells | Low (small cells) |
| Serum iron | Iron circulating right now | Low, but it fluctuates by the day |
| Transferrin | The transport protein for iron | High (body grabs extra iron) |
| Transferrin saturation | Percentage of transferrin carrying iron | Below 20% |
Ferritin is the most sensitive marker and falls first, so it is the value you definitely want measured. Transferrin saturation helps when in doubt, for example when ferritin looks artificially high due to inflammation.
The difference between iron deficiency and iron-deficiency anaemia
This distinction decides how early you are.
- Iron deficiency: your ferritin is low, your haemoglobin is still normal. Stores are running out while your body compensates. You may already have symptoms.
- Iron-deficiency anaemia: your ferritin is low and your haemoglobin has dropped too. The advanced stage.
Do not wait for haemoglobin to fall. A low ferritin alone is reason to discuss things with your GP, especially with ongoing fatigue.
Haem versus non-haem iron: why your source matters
Not all dietary iron is absorbed equally well, which explains why some people keep a low ferritin despite eating "enough" iron. There are two forms:
- Haem iron from animal products (red meat, liver, fish) is absorbed relatively well, typically around a quarter of the amount you take in.
- Non-haem iron from plant sources (legumes, wholegrains, dark leafy greens) is absorbed far less well, often only a few percent.
The absorption of non-haem iron also depends strongly on what you eat alongside it. Vitamin C (a glass of orange juice, bell pepper, kiwi) measurably improves absorption, while tea, coffee and dairy at the same meal inhibit it. The Voedingscentrum (Netherlands Nutrition Centre) therefore advises combining plant iron with a vitamin C source and drinking strong tea or coffee between meals instead. For vegetarians and vegans this is not a detail but the heart of the matter: it is not only about how much iron you eat, but how much your body actually extracts.
When does an iron panel make sense?
An iron profile can bring clarity if you recognise one or more of these:
- Persistent fatigue without a clear cause
- Paleness, dizziness or shortness of breath on exertion
- Heavy menstruation
- A vegetarian or vegan diet
- Pregnancy or a wish to conceive
- Intensive sport (especially endurance training)
- Restless legs or hair loss
The Gezondheidsraad lists young women, pregnant women and people on a one-sided or plant-based diet as groups at higher risk of low iron intake. The NHG (Dutch College of General Practitioners) guideline on anaemia advises doctors to assess iron metabolism specifically in microcytic anaemia (low MCV), precisely because haemoglobin alone says too little.
How to prepare for the test
The test is a standard blood draw at a collection point. For the most reliable result:
- Have your blood drawn in the morning if possible.
- Pause iron supplements 24 hours before the draw, otherwise serum iron can be distorted.
- Fasting is not strictly required, but it can sometimes ease interpretation.
Frequently asked questions
Is a haemoglobin measurement alone enough?
No. Haemoglobin only drops once the deficiency is well advanced. Ferritin falls first and is the most sensitive marker, so a normal haemoglobin does not rule out iron deficiency.
Can my ferritin look normal while I am still deficient?
Yes. Inflammation raises ferritin artificially because it is also an acute-phase protein. Your doctor can then add transferrin saturation or CRP to uncover the real iron level.
How long does recovery take?
With supplementation, haemoglobin usually rises within 4 to 8 weeks. Replenishing ferritin (the store) takes longer, on average 3 to 6 months. Do not stop too early, in consultation with your doctor.
Does iron deficiency always cause anaemia?
No. Iron deficiency starts with a low store (low ferritin) while your haemoglobin is still normal. Only as the deficiency worsens does your haemoglobin fall and do you speak of iron-deficiency anaemia. It is precisely in that early stage that you can already be tired without a standard blood count showing anything, which is why looking specifically at ferritin is so valuable.
Want the full picture? A focused iron studies panel measures ferritin, iron and transferrin together, and if anaemia is suspected, an anaemia panel helps. Prefer to choose your own values? Build a custom blood test. Read our explainer on the ferritin level and on anaemia too. Every result at Vitalcheck is reviewed by a registered doctor. A blood value is not a diagnosis: discuss symptoms and treatment with your GP.
Sources
- NHG guideline Anaemia. Dutch College of General Practitioners. Accessed 2026.
- Gezondheidsraad (Health Council of the Netherlands). Dietary reference values for vitamins and minerals. 2018.
- Voedingscentrum (Netherlands Nutrition Centre). Iron. Accessed 2026.
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