Why ferritin isn't as simple as an iron test

Ferritin is unusual among biomarkers because the same elevated number can mean two almost opposite things: too much stored iron, or inflammation with completely normal iron. It's the protein that stores iron in your body, and because it's more stable day-to-day than a standard iron test, it gives a better read on your long-term reserves. But your body also raises ferritin on purpose during illness or inflammation, pulling iron away from bacteria and viruses that need it to multiply. That means a high result doesn't automatically mean iron overload, and a normal result doesn't always rule out a problem either. Here's how to actually read your number.

The Basics

What it is

Ferritin is the protein that stores iron in your liver, spleen, and bone marrow, and it reflects your long-term iron reserves better than a same-day iron blood test does.

Why it matters

It does double duty as both an iron marker and an inflammation marker, since your body deliberately raises ferritin during infection or inflammation regardless of how much iron you actually have. Reading it alongside a marker like CRP is usually what tells you which one you're looking at.

Healthy range

Roughly 16 to 154 ng/mL for women aged 19 to 40, and 38 to 380 ng/mL for men aged 19 to 59; ranges shift further with age.

What moves it

Vegetarian or vegan diets, and iron-blocking foods like tea or coffee taken with meals, tend to lower it; pregnancy, alcohol, liver disease, and inflammation all tend to raise it. Recent infection, intense exercise, or dehydration can also temporarily skew a single reading.

When to test

Consider testing if you have unexplained fatigue, hair loss, or restless legs (which can point to deficiency), or joint pain and fatigue with a family history of hemochromatosis (which can point to overload). Otherwise, annual screening is typically enough once you know your baseline.

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