# Ferritin
URL: https://genohealth.app/biomarkers/ferritin
Units: ng/mL (or µg/L — equivalent)
Functional optimal: 50-150 ng/mL (functional optimal for energy in adults)
Clinical reference: Women 15-200 ng/mL · Men 30-400 ng/mL (lab reference)
Evidence: Strong evidence
Last reviewed: 2025-06-30

## Summary
Ferritin reflects your body's iron stores. Low ferritin is one of the most common drivers of unexplained fatigue; very high ferritin can flag inflammation or iron overload.

## What it is
Ferritin is the body's main iron-storage protein. Serum ferritin levels correlate with total body iron stores in the absence of inflammation. It is the best single test for diagnosing iron deficiency.

## Why it matters
Iron deficiency — even before anemia develops — causes fatigue, hair loss, exercise intolerance, restless legs, and cognitive sluggishness. On the other end, persistently elevated ferritin can flag inflammation, fatty liver, or hereditary hemochromatosis (HFE variants).

## Causes of high
- Inflammation (ferritin is an acute-phase reactant) — pair with CRP
- Hereditary hemochromatosis (HFE C282Y / H63D variants)
- Metabolic / fatty liver disease
- Frequent blood transfusions, iron overload
- Alcohol use

## Causes of low
- Inadequate dietary iron, plant-based diets without planning
- Heavy menstrual bleeding
- Gastrointestinal blood loss (ulcers, colon cancer screening matters)
- Pregnancy — increased demand
- Malabsorption (celiac disease, H. pylori, after bariatric surgery)
- Endurance athletes — high turnover plus footstrike hemolysis

## Lifestyle
- Investigate heavy menstrual bleeding or GI symptoms early
- Donate blood if ferritin runs very high in healthy adults — under medical guidance

## Nutrition
- Heme iron sources (red meat, poultry, fish) absorb best
- Pair plant iron (lentils, spinach, tofu) with vitamin C to boost absorption
- Coffee and tea reduce non-heme iron absorption — separate by 1-2 hours from iron-rich meals or supplements
- For supplements, ferrous bisglycinate is well tolerated; take every other day for better absorption

## Testing notes
Always interpret ferritin alongside hemoglobin, transferrin saturation, and CRP. Inflammation can artificially raise ferritin and mask true deficiency.

## Related (knowledge graph)

### Symptoms
- Fatigue (/symptoms/fatigue): Iron deficiency (ferritin < 50) is one of the most common reversible causes of chronic fatigue. [Strong evidence]

## FAQ
**Q: What ferritin level causes fatigue?**
A: Many people feel symptoms — fatigue, hair shedding, exercise intolerance — when ferritin drops below 50 ng/mL, even though most labs only flag deficiency under 15-30 ng/mL. Restoring ferritin into the 50-100 range often resolves symptoms.

**Q: Should I take iron if my ferritin is low?**
A: Talk to a clinician first. Replacing iron is usually appropriate, but the underlying cause (heavy periods, GI bleeding, malabsorption) needs investigation — otherwise it will recur.

**Q: What if my ferritin is very high?**
A: Persistently elevated ferritin warrants checking transferrin saturation and inflammatory markers. If transferrin saturation is also high, HFE genetic testing for hereditary hemochromatosis is reasonable.

## Citations
- Camaschella, NEJM 2015 — Iron deficiency anemia (PMID 25946282): Ferritin < 30 ng/mL is highly specific for iron deficiency; symptomatic deficiency can occur up to ~50 ng/mL.
- Adams et al., NEJM 2005 — HFE hemochromatosis (PMID 15858186): HFE C282Y homozygosity is the most common cause of hereditary iron overload in people of Northern European descent.

Disclaimer: Informational only — not medical advice.