What Is Ferritin?
Ferritin is a protein that stores iron inside your cells. A blood ferritin test reflects your total body iron reserves — it's the single best screening test for iron deficiency, and one of the most clinically actionable biomarkers you can track.
Unlike hemoglobin (which only drops once iron deficiency is severe), ferritin falls early — often months before you'd be diagnosed with anemia. This makes it a leading indicator: catch it early, fix it early.
Optimal Ranges by Demographic
| Group | Standard Range | Optimal Range | Unit | |-------|---------------|---------------|------| | Adult Men | 30–300 | 50–150 | ng/mL | | Adult Women (pre-menopausal) | 20–200 | 50–100 | ng/mL | | Adult Women (post-menopausal) | 30–300 | 50–150 | ng/mL | | Athletes (endurance) | 30–300 | 80–150 | ng/mL |
A ferritin below 30 ng/mL is diagnostic of iron deficiency in most clinical contexts, even with normal hemoglobin. Functional medicine practitioners target 50–150 ng/mL for optimal energy and cognition.
What Low Ferritin Means
Iron deficiency is the most common nutritional deficiency worldwide. Symptoms include:
- Fatigue and low energy — even before anemia develops
- Brain fog and poor concentration
- Hair loss and brittle nails
- Exercise intolerance — can't sustain effort
- Restless legs syndrome
- Cold intolerance
Women of reproductive age, endurance athletes, and vegetarians/vegans are at highest risk.
What High Ferritin Means
Elevated ferritin doesn't always mean excess iron. Common causes include:
- Chronic inflammation — ferritin is an acute phase reactant
- Metabolic syndrome — fatty liver elevates ferritin
- Hemochromatosis — genetic iron overload (check iron saturation to confirm)
- Liver disease — damaged hepatocytes release stored ferritin
Check iron saturation (Iron/TIBC x 100) to distinguish true iron overload from inflammation. GATOR calculates this ratio automatically.
How to Improve Low Ferritin
- Iron bisglycinate — better absorbed and fewer GI side effects than ferrous sulfate
- Pair iron-rich foods with vitamin C — doubles absorption
- Avoid tea and coffee within 1 hour of iron-rich meals — tannins block absorption
- Lactoferrin may improve absorption when standard supplements cause GI issues
Retest 8–12 weeks after starting supplementation. Iron stores take time to replenish.
Track Ferritin in GATOR
GATOR normalizes ferritin from Function Health, LabCorp, and InsideTracker. View your longitudinal trend on the Labs tab, see how ferritin correlates with your energy levels and exercise performance, and get AI insights when your levels change.
Learn more about ferritin in our biomarker glossary.