Ferritin is the protein that stores iron, and its blood level is the best single estimate of your iron reserves. It doubles as an inflammation marker, which is why a normal reading does not always mean iron stores are full.
Standard range versus optimal range
| Framework | Ferritin value | Source |
|---|---|---|
| Iron deficiency, healthy adults | below 15 µg/L | WHO 2020 |
| Iron deficiency with inflammation | below 70 µg/L in adults | WHO 2020 |
| Possible iron overload | above 150 in women, above 200 in men | WHO 2020 |
When it runs high
High ferritin can mean true iron overload, but far more often it reflects inflammation, infection, liver disease or metabolic syndrome, because ferritin rises as an acute phase reactant.
- Inflammation or infection, the most common cause
- Fatty liver and metabolic syndrome
- Excess alcohol intake
- Iron overload disorders such as hemochromatosis
- Frequent blood transfusions
- Some cancers and lymphomas
When it runs low
Low ferritin is specific for depleted iron stores and appears long before anemia develops. Fatigue, restless legs and hair shedding can occur at this stage even with a normal hemoglobin.
- Menstrual blood loss
- Low dietary iron or poor absorption
- Pregnancy demand
- Frequent blood donation
- Celiac disease or gastric surgery
- Chronic hidden bleeding from the gut
The warehouse inventory of iron
Think of ferritin as the stock count of the iron warehouse. Hemoglobin tells you whether the delivery trucks are loaded right now, ferritin tells you how much is left on the shelves. Stores run empty months before hemoglobin falls, so ferritin catches iron deficiency at the stage where fatigue and poor exercise tolerance are the only clues. The World Health Organization names it the best single marker of iron status for exactly this reason.
The inflammation trap
Ferritin climbs whenever the immune system is active, which protects microbes from your iron but muddies the reading. A person with true iron deficiency and a cold can show a falsely reassuring ferritin. WHO answers this by raising the deficiency threshold to 70 µg/L when inflammation is present, and by recommending a CRP measurement alongside. Very high values above 1000 µg/L are a different story and point toward iron overload disease, severe liver injury or rare immune storms.
How low is too low
The laboratory lower limit of 15 µg/L marks absent stores, not optimal ones. Studies of non-anemic women link fatigue relief to raising ferritin above roughly 50 µg/L, and many clinicians treat symptomatic patients well before the official cutoff. Context decides, and pairing ferritin with transferrin saturation separates empty shelves from inflammation.
Related calculators
Related biomarkers Transferrin Sat. · Hemoglobin · hs-CRP