Ferritin test: what the result means (FER)

Ferritin is a protein that binds iron and stores it inside cells — mostly in the liver, spleen and bone marrow. A small fraction circulates in the blood, and that fraction reflects the body's overall iron reserves. Because of this, a ferritin test is considered the single most accurate way to assess iron stores: reserves run low before haemoglobin actually drops, so ferritin can flag a deficiency before anaemia develops. Ferritin is also an acute-phase protein — it rises during inflammation or infection even when iron itself is not lacking. For that reason it's usually read together with CRP (C-reactive protein), serum iron and transferrin saturation.

• When a routine blood count shows low haemoglobin or haematocrit, with red cells that are smaller and carry less haemoglobin than usual — suspected iron-deficiency anaemia
• With ongoing tiredness, weakness, dizziness or headaches, shortness of breath, ringing in the ears, drowsiness or irritability
• With less typical signs: cracks at the corners of the mouth, spoon-shaped nails, a burning tongue, or cravings for non-food substances
• When iron overload (haemochromatosis) is suspected — joint pain, fatigue, changes in skin colour
• To track iron stores during pregnancy, in athletes, on a plant-based diet, or after significant blood loss

A raised ferritin doesn't automatically mean too much iron. Ferritin is an acute-phase protein, so it climbs with infection, inflammation, or after surgery. Other causes include liver disease, obesity, alcohol use, autoimmune conditions, an overactive thyroid, and hereditary haemochromatosis (inherited iron overload). CRP, liver markers and transferrin saturation help tell these apart.

• Inflammation or infection, including the period after surgery — ferritin rises as an acute-phase protein
• Liver disease
• Obesity
• Alcohol use
• Autoimmune conditions
• Overactive thyroid (hyperthyroidism)
• Cancer
• Haemochromatosis — an inherited condition where the body stores too much iron

Symptoms sometimes reported with a high ferritin

• Weakness or fatigue
• Joint pain (knees, hands)
• Abdominal pain
• Changes in skin colour — a greyish, metallic or bronze tint
• Reduced sex drive

A low ferritin points to depleted iron stores and is the most common cause of iron deficiency and iron-deficiency anaemia. Because stores run out before haemoglobin falls, a low ferritin can be the only abnormal finding while a routine blood count still looks normal. Common causes are not getting enough iron from food or poor absorption, blood loss (heavy periods, gastrointestinal bleeding, frequent blood donation), higher need during pregnancy, growth or intensive training, and digestive conditions that impair absorption, such as coeliac disease. Under WHO's guideline the threshold is 15 µg/l for adults, rising to 70 µg/l during inflammation.

Symptoms of depleted iron stores

• Shortness of breath
• Weakness or fatigue
• Dizziness
• Heart rhythm disturbances
• Pale skin
• Restless legs syndrome

Ferritin below 15 µg/l: per WHO's 2020 guideline, a ferritin below 15 µg/l in an adult with no inflammation or infection indicates iron deficiency. Iron stores are depleted at that point, but anaemia has not necessarily developed — haemoglobin usually falls later, once the stores are fully used up. WHO set this threshold for healthy adults and for children from age 5 with no signs of acute or chronic illness: ferritin then reflects the body's stores directly, because inflammation is not pushing it up. The result is normally read together with a full blood count and red-cell indices (MCV, MCH), to see whether the deficiency has already affected the red blood cells, and sometimes together with a search for a source of blood loss — heavy periods, gastrointestinal bleeding or frequent blood donation — especially when the deficiency recurs or diet does not explain it. A single low result diagnoses nothing on its own: if there were signs of infection at the time of the test, WHO raises the deficiency threshold to 70 µg/l, so a doctor weighs the number together with the overall clinical picture and, if needed, repeats the test after some time.

Ferritin 15-69 µg/l: in a healthy adult with no inflammation, WHO's 2020 guideline treats this as a normal range for iron stores, since the deficiency threshold there is 15 µg/l. The same guideline notes that ferritin rises temporarily during infection or inflammation, and in that situation the deficiency threshold is raised to 70 µg/l — so a value up to 69 µg/l measured during inflammation can still mean depleted stores. That is why this band is not read in isolation but alongside an inflammation marker, most often CRP (C-reactive protein): if CRP is raised, a lower value in this band is interpreted more cautiously; if there are no signs of inflammation, the same value is usually taken as a normal iron store. In practice one number in this band gives no unambiguous answer without context — a doctor weighs it together with general health, any signs of inflammation and, if needed, other iron markers.

Ferritin 70-149 µg/l: per WHO's 2020 guideline this sits above the deficiency thresholds even during inflammation, and below the levels WHO links to its iron-overload categories — which start at 150 µg/l for menstruating women and at 200 µg/l for men and non-menstruating women. A value here usually reflects adequate iron stores in a healthy adult, and the guideline does not attach a separate recommendation to this band, since it simply falls between the deficiency and overload thresholds already set. Ferritin in this band can still be slightly raised by inflammation, a liver condition or obesity without any real iron overload, so if there are additional symptoms or other abnormal results, a doctor may ask for CRP or liver markers. In someone healthy and without symptoms this band usually needs no further testing, but the context — age, sex, the other tests taken at the same time — is always weighed alongside the number itself.

Ferritin 150-199 µg/l: per WHO's 2020 guideline, this band in menstruating women who are otherwise healthy falls into the category linked to possible iron overload — and the guideline flags it as a conditional recommendation, based on earlier WHO positions rather than on strong evidence. For men and for women after menopause the corresponding threshold is higher, 200 µg/l, so the same value does not yet fall into that category for them. Because ferritin is an acute-phase protein, WHO stresses that a raised value alone cannot be used as the only means of identifying iron overload: the most common reasons are inflammation, liver disease, obesity or alcohol use rather than genuine iron accumulation. WHO therefore recommends a wider clinical and laboratory assessment to establish the cause at this level, instead of relying on this one result, and the final judgement is always the doctor's.

Ferritin 200-499 µg/l: per WHO's 2020 guideline, this band in men and in women after menopause who are otherwise healthy falls into the category linked to possible iron overload, the threshold for them being 200 µg/l. That is lower than the 500 µg/l threshold applied to people who already have an illness, because someone healthy and without other conditions is assessed differently from someone already ill. For menstruating women this band is also above the 150 µg/l threshold that applies to them. WHO states plainly that a ferritin concentration on its own cannot be used to establish an iron-overload category: someone with a value here needs a clinical and laboratory assessment to find the real cause, since common explanations include inflammation, liver disease, obesity or a cancer rather than iron accumulation alone. In practice this band is a signal for wider testing rather than an answer in itself — a doctor usually reads it together with transferrin saturation and liver markers.

Ferritin above 500 µg/l: per WHO's 2020 guideline, a ferritin above 500 µg/l in an adult who already has some illness may indicate iron overload or another condition, and calls for further clinical and laboratory assessment. The guideline marks this threshold as a conditional recommendation based on very low-certainty evidence, so the number is not a final answer in itself. The possible causes WHO and other sources mention include hereditary haemochromatosis, liver disease, frequent blood transfusions, chronic inflammation and some cancers — causes so different in nature that WHO recommends a broader assessment rather than relying on the ferritin figure alone. The liver is the main organ where iron accumulates, so when the cause needs clarifying, non-invasive tests such as magnetic resonance imaging may be used instead of a liver biopsy. Decisions about further testing are always made by a doctor, having weighed the whole clinical picture.

How the thresholds differ by group

Women and men: WHO's 2020 guideline applies the same iron-deficiency threshold to women and to men as to other adults — below 15 µg/l without inflammation, and below 70 µg/l during inflammation or infection. The overload-risk threshold is set lower for menstruating women, above 150 µg/l, while for women after menopause it is above 200 µg/l, as for men. When reading a result it therefore matters whether periods are still occurring, which reference interval the laboratory uses, and whether there was any inflammation at the time of the test.

Children: the guideline sets several thresholds by age. In children under 5 the iron-deficiency threshold is below 12 µg/l without inflammation and below 30 µg/l during inflammation or infection. For children from age 5 and for adolescents the thresholds match those for adults — below 15 µg/l without inflammation, below 70 µg/l with it. Knowing the child's exact age, and whether there were signs of inflammation at the time, matters when the result is assessed.

Pregnancy: the guideline gives a threshold only for the first trimester — below 15 µg/l, the same as for adults who are not pregnant. No separate numeric thresholds are given for the second and third trimesters. Plasma volume changes physiologically during pregnancy, and that can affect the ferritin concentration independently of the body's actual iron stores, so knowing the trimester and the measuring interval the laboratory uses both matter when the result is read.

What is usually checked next

Alongside a low ferritin, these are the things usually assessed:

• Whether there were signs of infection or inflammation at the time of the test
• A full blood count and iron markers (serum iron, transferrin saturation, TIBC) — to make clear whether anaemia is already present
• A possible source of blood loss — particularly in men and in women after menopause
• Diet, and conditions that impair iron absorption (coeliac disease, for example)
• When to repeat the test to see how the value changes

Alongside a high ferritin, the questions are different:

• Whether there was an infection or inflammation at the time of the test — worth assessing together with CRP
• Liver markers (ALT, AST, GGT) and transferrin saturation — they help separate inflammation from iron overload
• Family history: whether anyone in the family had haemochromatosis
• When to repeat the test so the change over time is visible

Paying privately, a ferritin test at a Lithuanian laboratory such as Medicina practica costs from €16 (September 2026 pricing). A family doctor can also order it free of charge when clinically indicated. Ferritin is usually read alongside a full blood count, which includes haemoglobin, and it is one of the tests used when iron-deficiency anaemia is suspected.