Ferritin

What is Ferritin?

Ferritin is the protein that stores iron inside your cells, mostly in the liver, spleen, and bone marrow. A small, stable amount circulates in your blood, and — as long as there is no inflammation — that circulating level tracks your total iron reserves closely. This makes serum ferritin the most clinically useful blood test for spotting iron deficiency before it becomes anaemia. It is reported in micrograms per litre (µg/L), numerically the same as ng/mL. The catch is that ferritin is also an acute-phase protein: it rises during infection, inflammation, liver injury, and heavy alcohol use, independent of how much iron you actually have. So a 'normal' or even high ferritin does not always rule out iron deficiency if inflammation is present — your iron stores can be low while inflammation props the number up. This is why ferritin is read alongside serum iron, transferrin, transferrin saturation, and an inflammation marker such as hs-CRP rather than on its own. The Optimize Baseline measures ferritin as part of its iron panel, together with serum iron and transferrin, so the number can be interpreted in context rather than in isolation.

Why is Ferritin relevant?

Ferritin matters because iron deficiency is one of the most common — and most missed — contributors to everyday fatigue, breathlessness on exertion, poor exercise recovery, brain fog, restless legs, and hair shedding. These symptoms can appear while stores are running down, often before haemoglobin falls and a formal anaemia shows up, so a low ferritin with a normal blood count is an early, actionable signal. Women with menstrual blood loss, pregnant people, endurance athletes, blood donors, and people on plant-based diets are the most likely to run low. As a general, lab-dependent reference, adult ferritin typically falls in the range of roughly 30–300 µg/L for men and 15–200 µg/L for women, with the exact bounds varying by laboratory, sex, and age. Dutch primary-care guidance (the NHG-Standaard Anemie) follows the same logic: a ferritin below 15 µg/L confirms iron deficiency, a value between 15 and 100 µg/L calls for extra context such as the MCV and an inflammation marker, and above roughly 100 µg/L iron-deficiency anaemia becomes unlikely. Note that some bodies — for example NICE in the UK and recent haematology panels for menstruating and pregnant people — use a higher cut-off of about 30 µg/L to improve sensitivity, which is why many clinicians treat a value under 30 µg/L as iron deficiency even when it sits inside the printed 'normal' range. Some endurance athletes and sports physicians also aim for a higher buffer above the lower limit, though the performance benefit of topping up stores once you are no longer deficient is not firmly established. These bands describe iron status — they are not a diagnosis on their own. At the other end, a persistently high ferritin is worth understanding rather than ignoring. It can reflect genuine iron overload (as in hereditary haemochromatosis), but in everyday practice it far more commonly signals inflammation, fatty liver, metabolic syndrome, or alcohol — each of which is more common than haemochromatosis. Transferrin saturation is the marker that helps tell true iron overload apart from an inflammatory or metabolic rise: a persistently raised saturation (roughly above 45% in women and 50% in men) together with a high ferritin is the pattern that points toward overload.

Ferritin high or low — what it means

A single ferritin value is a starting point, not a verdict. Because ferritin climbs with any infection, recent illness, hard training block, or inflammatory flare, an isolated reading taken when you are unwell can look reassuringly normal while your stores are actually low. For a trustworthy baseline, interpret ferritin alongside transferrin saturation, serum iron, and hs-CRP, and repeat it when you are well and free of infection. A low ferritin almost always means depleted iron stores, and the next question is why: menstrual or gastrointestinal blood loss, inadequate dietary iron, poor absorption (coeliac disease, certain medications, after weight-loss surgery), pregnancy, or frequent blood donation are the usual drivers. Persistent unexplained iron deficiency — especially in men and post-menopausal women — should be investigated for a source of bleeding rather than simply supplemented. A high ferritin needs the opposite reasoning. With a high transferrin saturation it may point to iron overload and warrants follow-up; with a normal or low saturation and a raised hs-CRP it is usually inflammation, infection, liver disease, or metabolic strain doing the work, not excess iron. Either way, a markedly or persistently high value deserves a conversation with a clinician. To raise a low ferritin, the realistic levers are addressing any source of blood loss, increasing dietary iron (red meat, poultry, fish, legumes, and leafy greens, with the better-absorbed haem form coming from animal sources), pairing plant iron with vitamin C and separating it from tea, coffee, and calcium, and — where diet is not enough — oral iron supplementation, or intravenous iron when oral iron fails or is poorly tolerated. Rebuilding stores is slow, so re-test after about 8–12 weeks rather than expecting a quick jump, and manage supplementation and any high or stubbornly low result under medical guidance.

Educational information only — not medical advice. Consult a healthcare professional for clinical decisions.