Ferritin Test: What Your Iron Stores Actually Show

What is a ferritin test?

A ferritin test is a blood test that measures ferritin, the protein that stores iron inside your cells. Because circulating ferritin broadly reflects the size of the body's iron reserves, it is the most sensitive single marker of iron deficiency and will usually fall before haemoglobin does. It is measured from a standard venous blood draw.

That sensitivity is why ferritin is worth measuring rather than relying on a full blood count alone. Haemoglobin can remain within range while iron stores are already depleted, which means anaemia is a late signal, not an early one.

What is a normal ferritin range?

Reference ranges are laboratory-specific and differ by sex. Commonly cited adult ranges are approximately 20 to 500 ng/mL for men and 20 to 200 ng/mL for women, as summarised by Lab Tests Online UK. Because the interval varies with assay and population, always read your result against the range printed on your own report.

There is an important gap between the statistical reference range and the level at which symptoms occur. A ferritin of 18 ng/mL may be flagged as low. A ferritin of 22 ng/mL sits inside the range and yet a substantial body of clinical practice treats levels in the twenties and thirties as consistent with symptomatic iron deficiency, particularly in menstruating women and endurance athletes. Being inside the reference range is not the same as being replete. EVA's own optimal range is 50 to 150 ng/mL. As with vitamin D, the wider laboratory reference interval and the narrower optimal range answer different questions: one describes the spread of results across a population, the other describes where EVA aims to bring a client.

What are the symptoms of low ferritin?

Low ferritin commonly presents as persistent fatigue, reduced exercise tolerance, breathlessness on exertion, pallor, hair shedding, brittle nails, cold intolerance, poor concentration and restless legs. These symptoms can appear while haemoglobin is still normal, because iron stores deplete before red cell production is affected.

The restless legs association is worth singling out because it is frequently missed. So is hair shedding, which people usually attribute to almost anything before iron.

The overlap with other deficiencies is also substantial. Vitamin D deficiency produces a very similar fatigue picture, which is why measuring one without the other frequently leaves the real cause unidentified. Cleveland Clinic and MedlinePlus both describe low ferritin as indicating depleted iron stores and set out the symptom pattern.

Why a normal ferritin does not always mean adequate iron

This is the single most important limitation of the test, and it is the reason ferritin should not be read in isolation.

Ferritin is an acute phase reactant. Its level rises in response to inflammation, infection, liver disease, recent alcohol intake, malignancy and metabolic dysfunction, independent of how much iron is actually stored. A person with genuine iron deficiency and a concurrent inflammatory state can produce a ferritin result that lands squarely inside the normal range.

The practical consequence is that a normal ferritin in the presence of raised inflammatory markers does not exclude iron deficiency. This is why ferritin is best interpreted alongside a full blood count, iron studies, meaning iron and total iron binding capacity, from which transferrin saturation is calculated, and an inflammatory marker such as hs-CRP. Testing.com covers the same interpretive caution.

There is a second knock-on effect worth knowing about. Iron deficiency can push an HbA1c result upward, which means an unrecognised low ferritin can make glucose control look worse than it is.

What does a high ferritin result mean?

High ferritin has two broad explanations and they are not equally common. The first is genuine iron overload, including hereditary haemochromatosis. The second, and considerably more frequent, is that ferritin has risen as an inflammatory or metabolic response, in the context of infection, liver disease, chronic inflammation, high alcohol intake or metabolic syndrome, with iron stores themselves normal.

Distinguishing the two requires additional testing rather than assumption. Transferrin saturation, calculated from iron and total iron binding capacity, is the usual next step: it is typically elevated in true iron overload and normal or low when ferritin is raised for inflammatory reasons. Mayo Clinic sets out both directions of abnormality.

Who should consider testing ferritin

Ferritin is worth measuring in anyone with unexplained fatigue, in menstruating women particularly with heavy periods, during pregnancy planning and pregnancy, in vegetarians and vegans, in endurance athletes, in people with coeliac disease, inflammatory bowel disease or previous bariatric surgery, in blood donors, and in anyone with a family history of haemochromatosis.

It is also the marker to check before starting iron supplementation rather than after. Supplementing iron without knowing baseline stores risks both under-treating a real deficiency and loading iron into someone who does not need it, which is the argument for personalised supplement protocols built from your results instead of a generic iron tablet.

How EVA measures and interprets ferritin

EVA™ is a direct-to-consumer platform. Blood samples are processed through Unilabs, our laboratory partner, and results are interpreted by the Elite Vita clinical team. EVA measures more than 70 blood biomarkers across seven body systems, so ferritin arrives alongside the markers needed to interpret it.

Ferritin is a good illustration of why interpretation matters more than the number. A ferritin of 24 ng/mL returned against a reference range starting at 20 will be reported as normal. Read alongside a symptom history of fatigue and hair shedding, a normal haemoglobin and a low-normal transferrin saturation calculated from your iron studies, the same result reads as depleted stores that have not yet produced anaemia. A raised ferritin read alongside a raised hs-CRP points somewhere quite different from the same figure in isolation. That is the work the clinical layer does, and you can read more about the clinical standards behind that interpretation.

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