Ferritin explained: what is an optimal level for energy and health

Ferritin reflects the body’s iron stores – but the standard lab range (15–300 µg/L) means you can be deeply iron-deficient without anaemia while hemoglobin is still normal. Here is what a functionally optimal ferritin looks like, why it drops and when it is truly too high.

What ferritin actually measures

Ferritin is the protein that stores iron in the liver, spleen and bone marrow. Serum ferritin reflects total body iron stores: 1 µg/L ≈ 8 mg of stored iron (Cook et al., Blood 2003). It is a more sensitive marker than hemoglobin – hemoglobin only drops once stores are already empty.

Lab range vs functional optimum

• Lab range: 15–300 µg/L (women), 30–400 µg/L (men)
• WHO iron-deficiency cutoff: < 15 µg/L (< 30 µg/L with chronic inflammation)
• Educational target discussed in the literature (not a diagnostic cutoff): 70–150 µg/L
• Below 30 µg/L: fatigue, hair loss, restless-legs – before anaemia sets in (Soppi, 2018)

Why ‘normal’ is not the same as optimal

Ferritin 20 µg/L is formally ‘normal’ – but that is ~160 mg of stored iron, barely enough for a single menstrual cycle. Levels below 40–50 µg/L correlate with chronic fatigue, restless legs and hair loss even when hemoglobin is normal (Camaschella, NEJM 2015).

High ferritin – two very different causes

• Real iron overload: hereditary hemochromatosis, frequent transfusions – ferritin persistently > 300–500 µg/L, transferrin saturation > 45%
• Inflammation marker: ferritin is an acute-phase protein. Chronic inflammation, fatty liver (MAFLD), metabolic syndrome, infection all raise ferritin without actual iron excess (Kell & Pretorius, 2014)