# Ferritin

Ferritin is the protein your cells use to store iron, and a little of it leaks into your blood. That is why serum ferritin is the go-to blood test for your total iron stores. Low ferritin (usually under 30 µg/L, or under 15 in some guidelines) means your iron is running out, even before it shows up as anemia. It can cause fatigue, worse exercise capacity, foggy thinking, and hair loss while your hemoglobin still looks normal. High ferritin is trickier, because it is also an 'acute-phase reactant': it jumps with inflammation, infection, liver disease, obesity, and metabolic syndrome. So a high reading does not automatically mean iron overload. If those causes are ruled out and it stays high, it may point to hereditary hemochromatosis or other iron overload, which drives oxidative stress, liver scarring, and heart-muscle damage. The best target is debated. Many longevity-minded doctors aim for roughly 70 to 120 µg/L, and watch out at both extremes.

## Sources

- Wang W, Knovich MA, Coffman LG, Torti FM, Torti SV. (2010). Serum ferritin: Past, present and future. Biochimica et Biophysica Acta. https://doi.org/10.1016/j.bbagen.2010.03.011
- Kim CH, Kim HK, Bae SJ, Park JY, Lee KU. (2011). Association of elevated serum ferritin concentration with insulin resistance and impaired glucose metabolism in Korean men and women. Metabolism. https://doi.org/10.1016/j.metabol.2010.03.007
- Ferrucci L, Corsi A, Lauretani F, Bandinelli S, Bartali B, Taub DD, Guralnik JM, Longo DL. (2005). The origins of age-related proinflammatory state. Blood. https://doi.org/10.1182/blood-2004-07-2599

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_Canonical: https://longevity-switzerland.com/en/glossary/ferritin · Part of Longevity Cities · Updated 2026-06-22_