Ferritin and iron test

Iron deficiency is one of the most commonly missed causes of persistent fatigue, because your haemoglobin can still look fine while your store is nearly empty. That store is what ferritin measures.

Iron status consists of four values that complement each other. Ferritin is your store. Serum iron is what circulates at that moment and fluctuates over the day. Transferrin is the transport protein, and transferrin saturation shows what share of it is actually loaded.

Measuring haemoglobin alone is not enough. Your body keeps haemoglobin up as long as it can by drawing down the store first. Anaemia is therefore the late stage, not the first signal.

When to measure this

• With persistent fatigue, even if an earlier blood count was normal.
• With heavy or prolonged periods. See womens hormones.
• If you eat little or no meat. See the vegan page.
• With endurance sport, where loss and increased turnover deplete the store slowly.
• With hair loss, breathlessness on exertion or restless legs.
• If you supplement iron and want to know whether it is landing. Measure after 8 to 12 weeks.

What is actually drawn

For a complete picture the blood count belongs with it: haemoglobin, haematocrit, MCV and MCH. That is in the Basic Panel.

Preparation

No fasting needed, but serum iron peaks in the morning, so a morning draw gives a more consistent picture. If you supplement iron, skip the dose that day. Ferritin rises with inflammation and after an infection, so do not draw in the week you have been ill, or your store will look fuller than it is.

Which package includes this

Measuring this marker on its own is possible too. The four iron values are determined together, because ferritin alone can mislead when inflammation is present. For reference, providers with a collection point typically charge 59 to 69 euro for a single marker, and you travel there yourself.

What your result means

A low ferritin with a normal haemoglobin means your store is falling while production still holds. That is exactly the stage at which you can act. A high ferritin does not necessarily mean iron overload, because inflammation raises it too. That is why hs-CRP often sits in the same panel.

Alongside the lab reference you get the stricter target range, because the floor used by many laboratories is low compared to what is considered comfortable in practice.

On the difference between a lab reference and a target range, see this article. If you feel unwell while your value sits inside the reference, read this one.