Markers · Iron
Ferritin low, or ferritin fine, and either way you're still tired. Ferritin, read against the rest of you.
What Ferritin measures, what it does in the body, why it's tested, and the two ranges it's read against. Everything said about the marker here comes from Merlin's own biomarker catalogue.
What Ferritin is
Ferritin is the primary intracellular iron storage protein and serves as the most sensitive indicator of the body's total iron stores. Low ferritin levels indicate depleted iron reserves and are the earliest detectable sign of iron deficiency, even before anemia develops. Elevated ferritin can signal iron overload, but it is also an acute-phase reactant that rises with inflammation, infection, liver disease, and metabolic conditions, requiring careful clinical interpretation.
What it does in the body
Ferritin stores iron within cells primarily in the liver, spleen, and bone marrow, releasing it as needed for erythropoiesis, oxygen transport, and enzymatic reactions. It plays a critical role in regulating iron homeostasis, protecting cells from iron-mediated oxidative damage, and supporting immune function, energy metabolism, and thyroid hormone synthesis.
Why it's tested
Ferritin testing is used to diagnose and monitor iron deficiency anemia, iron overload disorders such as hemochromatosis, and to differentiate anemia of chronic disease from true iron deficiency. It is also used to assess iron status in at-risk populations including pregnant women, athletes, vegetarians, and individuals with chronic inflammatory or gastrointestinal conditions.
The two ranges
The reference range reflects population statistics. The target reflects physiology.
- Lab reference range
- Women: 12-150 ng/mL; Men: 12-300 ng/mL (laboratory reference range varies by lab and age)
- Functional target
- Women: 50-150 ng/mL; Men: 70-200 ng/mL (functional optimum for energy, cognition, and thyroid function)
Those are different numbers, and you deserve to know which one you're looking at. Merlin reads your result against both.
Where this lives
A Field Guide to Fatigue & Malaise
The field guide that covers Ferritin in depth, whole and public.
In a real read
Ferritin sits in the real Cardiovascular read on this site as one of the nineteen biomarkers read in context: 98 ng/mL and unremarkable, which is the point. A number that's fine still gets read, and its being fine is part of what the other numbers mean.
A real Cardiovascular surface from a real anonymized panel: the score, the narrative, the layers underneath. Yours will be built the same way, on your own numbers.
Educational context for your conversations with your licensed healthcare provider, not a diagnosis or a treatment plan. Merlin reads results; it doesn't diagnose.
Bring the panel this number came from. Merlin reads it against everything else you have, every system and every year, then shows you what it means and what's worth finding out next. Start with your first month.
Start your first month - $35