How to Explain Ferritin to a Patient
Ferritin is a protein in your blood that tells us how much iron your body has stored away, like checking the fuel gauge in your car—it shows whether your iron "tank" is empty, full, or somewhere in between.
What Ferritin Measures
Ferritin reflects the iron stored in your liver, spleen, and bone marrow 1. Under normal conditions, each 1 µg/L of ferritin in your blood roughly equals about 10 mg of stored iron in your body 1. Think of it as your body's iron savings account.
Normal Ranges
- Men: Average around 135 µg/L 1
- Women: Average around 43 µg/L 1
- Young children (6-24 months): Around 30 µg/L 1
Understanding Your Results
Low Ferritin (Iron Deficiency)
When ferritin drops below certain levels, it signals your iron stores are depleted:
- Below 30 µg/L: Strong indicator of iron deficiency in most people 2
- Below 15 µg/L: Confirms iron deficiency with very high certainty 1
- Below 45 µg/L: Used as a diagnostic threshold when evaluating anemia 3
Low ferritin means your body doesn't have enough iron stored to make healthy red blood cells, which can lead to fatigue, weakness, and anemia.
High Ferritin (Multiple Possible Causes)
Here's the tricky part: High ferritin doesn't always mean too much iron. Ferritin is also an "acute phase reactant," meaning it rises during inflammation, infection, or illness—even when iron stores are normal or low 1, 4.
High ferritin can indicate:
- Iron overload (too much iron stored in organs)
- Inflammation or infection (arthritis, hepatitis, chronic diseases)
- Liver disease (hepatitis, fatty liver, cirrhosis) 4
- Cancer or lymphoma 4
- Metabolic syndrome (obesity, diabetes) 5, 6
- Alcohol use 6
Important Context for Inflammatory Conditions
If you have chronic inflammation or kidney disease, ferritin levels need different interpretation 7, 8:
- Without inflammation: Ferritin <30 µg/L indicates iron deficiency
- With inflammation present: The threshold increases to <100 µg/L to diagnose iron deficiency 8
This is because inflammation artificially raises ferritin levels, potentially masking true iron deficiency 1, 8, 4.
What Happens Next
If Your Ferritin is Low
Your doctor will likely recommend iron supplementation (pills or IV infusions) and investigate why you're losing or not absorbing iron properly 2, 9.
If Your Ferritin is High
Your doctor will order a transferrin saturation test to determine if the high ferritin is from iron overload or another cause 4, 5. This combination helps distinguish between:
- True iron overload (both ferritin and transferrin saturation elevated)
- Inflammation/other causes (ferritin high, transferrin saturation normal or low)
If ferritin is >1000 µg/L, referral to a specialist is typically recommended 6.
Key Takeaway
Ferritin is your body's iron storage indicator, but it's not perfect—it can be affected by inflammation, infection, and various diseases. That's why your doctor interprets it alongside your symptoms, other blood tests, and medical history to determine what's really happening with your iron levels 1, 2, 4.