Picture your iron balance as a bank account. Your haemoglobin is the money in your current account, which you spend every day. Your ferritin is your savings account, the buffer for leaner times. And just like with money: your savings run out before your current account is empty. That is why ferritin gives such a powerful early warning.
My view: relying on haemoglobin alone means looking too late. Ferritin falls months earlier, and that head start is exactly what you want to use.
How does iron storage via ferritin work?
Your body stores iron as ferritin, mainly in your liver, spleen and bone marrow. When your body needs iron, for example to make new red blood cells, ferritin releases it. This system stops you from burning through all your iron after every meal.
Every day you lose a small amount of iron through your skin, gut and urine. Women also lose iron during menstruation. If the loss is structurally greater than your intake, your ferritin levels fall gradually.
Why does ferritin fall first?
Ferritin is the earliest marker of iron deficiency. The deficiency unfolds in stages, and by measuring ferritin you catch the first stage.
| Stage | What happens | What you see in the blood |
|---|---|---|
| 1 | Iron store becomes depleted | Ferritin falls, haemoglobin still normal |
| 2 | Transport comes under pressure | Serum iron and transferrin saturation fall |
| 3 | Red cell production suffers | Haemoglobin and MCV fall: iron-deficiency anaemia |
By measuring ferritin you can catch stage 1 long before stage 3 (overt anaemia) is reached.
Risk groups for low ferritin
- Women with heavy menstruation: monthly blood loss is the most common cause of low ferritin
- Pregnant women: iron needs rise sharply during pregnancy
- Vegetarians and vegans: plant iron (non-haem) is absorbed less well than animal iron (haem)
- Intensive athletes: heavy exertion increases iron use
- People with gut complaints: coeliac disease and inflammatory bowel disease can disrupt absorption
The Gezondheidsraad (Health Council of the Netherlands) counts young women and pregnant women among the groups at higher risk of low iron intake.
When is ferritin actually too high?
Iron storage can also tip the other way. A high ferritin does not automatically mean iron overload, because ferritin also rises with inflammation, liver disease and heavy alcohol use. Still, there is one condition you do not want to miss: haemochromatosis, a hereditary form of iron overload where the body structurally absorbs too much iron. Over time, that iron can accumulate in organs such as the liver and heart. With a persistently high ferritin, especially in men or after the menopause, your doctor can run further tests, for example transferrin saturation, to distinguish iron overload from inflammation. The point: ferritin tells you not only whether your store is too low, but also whether it might be too high.
Raising ferritin: practical tips
- Eat iron-rich foods: red meat, legumes, dark leafy greens, pumpkin seeds.
- Combine plant iron with vitamin C (orange, bell pepper, kiwi) for better absorption.
- Avoid tea, coffee and dairy right at iron-rich meals, as they inhibit absorption.
- Consider an iron supplement only with a confirmed deficiency, in consultation with your doctor.
The Voedingscentrum (Netherlands Nutrition Centre) stresses that combining with vitamin C measurably improves the absorption of plant iron, an easy win for those who eat little meat.
When to test ferritin?
A ferritin test is useful if you are persistently tired, belong to a risk group, eat vegetarian or vegan, train intensively, or want to check your iron status preventively.
Frequently asked questions
What is the difference between ferritin and iron in the blood?
Serum iron measures the iron circulating at that moment, which fluctuates through the day and after meals. Ferritin measures your store: how much your body holds in reserve. Ferritin is therefore a more reliable measure of your iron status.
Can I get too much ferritin from iron tablets?
Yes, prolonged unnecessary use of high doses can lead to iron overload. Take supplements only with a proven deficiency and under guidance, and check your ferritin after about 3 months.
How long must I take iron to normalise my ferritin?
On average 3 to 6 months after your haemoglobin is already normal. Your doctor can advise continuing until your ferritin sits at a stable, sufficient level.
Does taking iron every other day work better than daily?
There are indications that iron is absorbed less well when taken too often, because a high intake temporarily activates an absorption blocker in your body. Some doctors therefore advise every other day rather than several times a day. It often also reduces stomach complaints. Follow your own doctor's advice here, because the ideal dose depends on your situation.
Want to map your iron store? An iron studies panel measures ferritin and transferrin together, or build a custom blood test. Read also how to detect iron deficiency and what your ferritin level means. 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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