Ferritin Explained
The most sensitive indicator of iron status — but also an acute phase reactant that rises with inflammation, making context critical for interpretation.
Who is this especially useful for?
- ✓Women with heavy menstrual cycles (most common cause of deficiency)
- ✓Vegetarians and vegans (non-heme iron is less bioavailable)
- ✓Endurance athletes (foot-strike hemolysis, sweat losses)
- ✓People experiencing unexplained fatigue, hair loss, or brain fog
- ✓Those with digestive issues affecting absorption (celiac, IBD, low stomach acid)
- ✓Men and postmenopausal women monitoring for iron overload
- ✓Anyone taking medications that affect iron absorption (PPIs, antacids)
Iron deficiency is the most common nutritional deficiency worldwide, affecting an estimated 2 billion people.
Ferritin is a protein that stores iron inside your cells, primarily in the liver, spleen, and bone marrow. Your blood ferritin level reflects these iron stores — when stores are depleted, ferritin drops; when stores are full, ferritin rises.
But here's the catch: ferritin is also an acute phase reactant. This means it rises during inflammation, infection, or illness — even if your actual iron stores are low. This dual nature makes ferritin both valuable and potentially misleading without proper context.
How to Test Ferritin Correctly
Ferritin testing requires context. Here's what you need to know:
💡 Pro tip: If your ferritin looks "normal" but you have symptoms of deficiency AND elevated CRP, retest when inflammation has resolved. True iron status may be much lower.
Where to find your Ferritin result
Ferritin without CRP is an incomplete picture. Always interpret together.
What is Ferritin?
Ferritin is a spherical protein shell that can hold up to 4,500 iron atoms in a safe, non-toxic form. Think of it as your body's iron savings account — iron is deposited when intake exceeds needs and withdrawn when demand increases.
Unlike hemoglobin (which carries oxygen) or serum iron (which represents iron in transit), ferritin reflects your total body iron reserves. This makes it the most sensitive early indicator of iron deficiency — ferritin drops before hemoglobin falls.
However, ferritin's role as an acute phase reactant means it can rise 2-4x during inflammation, masking underlying deficiency. This is why the WHO recommends adjusting ferritin interpretation when CRP is elevated.
Why CRP Context is Essential
The World Health Organization recommends adjusting ferritin interpretation when inflammation is present:
CRP < 5 mg/L
No adjustment needed — interpret ferritin at face value
CRP 5-10 mg/L
Mild inflammation — ferritin may be elevated 20-30% above true value
CRP > 10 mg/L
Significant inflammation — ferritin unreliable; retest when resolved or use other markers
Some researchers suggest using a ferritin cutoff of 70 ng/mL (instead of 30) when CRP is elevated to account for inflammation-driven elevation.
2B
People Affected
Iron deficiency affects ~2 billion people globally
World Health Organization
57%
Missed by Standard Cutoffs
Of women with "normal" ferritin were actually deficient using optimal thresholds
Koperdanova & Cullis, 2015
<30
Symptom Threshold
ng/mL — where fatigue, hair loss, and other symptoms often appear
Rushton & Barth, 2010
What Research Shows
The landmark Koperdanova paper found that using traditional "normal" ranges (15-150 for women) missed the majority of functional iron deficiency. When researchers used optimal thresholds (ferritin > 50 ng/mL), they identified iron deficiency in 57% of women previously classified as "normal." Symptoms like fatigue and hair loss often appear at ferritin levels of 30-50 ng/mL — well within conventional "normal" ranges.
Systematic review of ferritin interpretation in clinical practice
How Different Paradigms Interpret Ferritin
Ferritin interpretation varies dramatically by paradigm — and by gender:
Standard Medical View
Thresholds: Men: < 30 deficient, 30-400 normal, > 400 elevated | Women (premenopausal): < 15 deficient, 15-150 normal, > 150 elevated
Ranges designed to detect frank deficiency (anemia) and iron overload (hemochromatosis). Values within range considered adequate. Focus on preventing disease states rather than optimizing function.
Supplement only if hemoglobin is low AND ferritin depleted. Investigate elevated ferritin for hemochromatosis or liver disease. Routine screening not typically recommended.
Research Consensus View
Thresholds: Men: < 50 deficient, 50-100 suboptimal, 100-200 optimal, > 300 elevated | Women: < 30 deficient, 30-50 suboptimal, 50-100 optimal, > 100 investigate
Traditional cutoffs miss early depletion. Symptoms (fatigue, hair loss, restless legs, brain fog) often appear at ferritin 30-50 ng/mL — well within "normal" range. Optimal energy and function require adequate stores, not just absence of anemia.
Target 50-100 ng/mL for women, 100-200 ng/mL for men. Always interpret with CRP. Consider iron-rich foods or gentle supplementation. Every-other-day iron dosing may improve absorption.
Metabolic Optimization View
Thresholds: Men: < 100 low for carnivore, 100-200 optimal, 200-350 high normal, > 350 consider donation | Women: < 50 low, 50-100 optimal
On animal-based diets, ferritin naturally runs higher due to heme iron bioavailability — this is expected, not pathological. However, excessive iron accumulation increases oxidative stress and is associated with increased disease risk. Blood donation is a powerful health intervention for iron-replete individuals.
Women: ensure adequate intake, especially if restricting red meat. Men on carnivore: monitor for accumulation, consider donating blood every 2-4 months if ferritin > 300. Always check CRP to rule out inflammation-driven elevation. Consider HFE genetic testing if persistently elevated.
Why Gender Matters for Ferritin
Men and women have fundamentally different iron dynamics:
Premenopausal Women
Lose iron monthly through menstruation (30-80 mL blood = 15-40 mg iron). Pregnancy further depletes stores. Chronic undereating of red meat compounds the problem.
Typical ferritin: Often 15-50 ng/mL — "normal" but symptomatic
Primary risk: Deficiency is common; excess is rare
Men & Postmenopausal Women
No regular iron loss mechanism. Iron accumulates over time, especially with high red meat intake. Body has limited ability to excrete excess iron.
Typical ferritin: Often 100-300 ng/mL on Western diets
Primary risk: Accumulation and overload are the primary concerns
This is why blood donation is especially valuable for men and postmenopausal women — it's the primary way the body can reduce iron stores.
Signs of Iron Deficiency
Symptoms often appear before ferritin drops into "deficient" range on standard tests:
Fatigue and low energy
The most common symptom; often dismissed as "normal"
Hair loss or thinning
Especially diffuse thinning, not pattern baldness
Brain fog and poor concentration
Iron is essential for neurotransmitter function
Restless legs syndrome
Strong association with low ferritin
Shortness of breath
With exertion; reduced oxygen-carrying capacity
Cold hands and feet
Poor circulation and reduced metabolic rate
Brittle nails or spoon nails
Koilonychia — nails curve upward
Pale skin and inner eyelids
Reduced hemoglobin shows in mucous membranes
Many people with ferritin 20-40 ng/mL have these symptoms despite being told their levels are "normal."
How to Optimize Your Ferritin
Strategies differ depending on whether you need to raise or lower ferritin:
For Low Ferritin
Prioritize heme iron sources
Red meat, liver, oysters — 5-10x better absorbed than plant iron
Every-other-day supplementation
Research shows better absorption than daily dosing (Stoffel 2017)
Pair with vitamin C
Enhances non-heme iron absorption; take together
Avoid inhibitors with iron-rich meals
Coffee, tea, calcium, and phytates reduce absorption
For Elevated Ferritin
Rule out inflammation first
Check CRP — elevated ferritin with high CRP may be misleading
Donate blood regularly
Most effective way to reduce iron; benefits cardiovascular health
Reduce red meat temporarily
If ferritin > 300 and CRP is normal
Consider genetic testing
HFE gene mutations cause hereditary hemochromatosis
Iron Supplementation Considerations
If supplementation is needed, form and timing matter:
Ferrous bisglycinate (chelated)
Often preferred for sensitive individuals
Ferrous sulfate
Traditional form; effective but less tolerated
Iron from food
4 oz beef liver = ~5mg highly bioavailable iron
Research suggests every-other-day dosing (e.g., 30-60mg elemental iron) may be more effective than daily supplementation due to hepcidin dynamics. Take on an empty stomach with vitamin C for best absorption; if GI upset occurs, take with a small meal.
Blood Donation as Health Intervention
For those with adequate or elevated ferritin, regular blood donation offers multiple benefits:
- ✓Reduces iron stores by ~30 ng/mL per donation
- ✓Associated with reduced cardiovascular disease risk in men
- ✓Stimulates fresh red blood cell production
- ✓May reduce oxidative stress from excess iron
- ✓Helps others while improving your health
Men and postmenopausal women with ferritin > 150 ng/mL may benefit from donating every 2-4 months. Those with hereditary hemochromatosis may need therapeutic phlebotomy more frequently.
Typical Improvement Timeline
Ferritin rises slowly — expect 3-6 months to see meaningful improvement with supplementation or dietary changes. Symptoms like fatigue may improve within 4-8 weeks as functional iron improves, even before ferritin normalizes. After blood donation, ferritin typically drops ~30 ng/mL per donation and takes 8-12 weeks to recover.
Key Takeaways
- 1ALWAYS test ferritin WITH CRP — inflammation falsely elevates ferritin
- 2Standard "normal" ranges miss early deficiency; symptoms often appear at 30-50 ng/mL
- 3Gender matters: women typically need to raise ferritin; men often need to prevent accumulation
- 4Heme iron (from meat) absorbs 5-10x better than non-heme iron (from plants)
- 5Every-other-day supplementation may be more effective than daily
- 6Blood donation is therapeutic for iron-replete individuals, especially men
- 7If ferritin is persistently elevated with normal CRP, consider HFE genetic testing
References
- World Health Organization (2011). Serum ferritin concentrations for the assessment of iron status and iron deficiency in populations. Vitamin and Mineral Nutrition Information System, WHO/NMH/NHD/MNM/11.2.
- Koperdanova M, Cullis JO (2015). Interpreting raised serum ferritin levels. BMJ, 351, h3692. PMID: 26239322
- Stoffel NU, et al (2017). Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Am J Clin Nutr, 106(6), 1453-1461. PMID: 28978540
- Camaschella C (2015). Iron-deficiency anemia. N Engl J Med, 372(19), 1832-1843. PMID: 25946282
- Peyrin-Biroulet L, et al (2015). Guidelines on the diagnosis and management of iron deficiency across indications: a systematic review. Am J Clin Nutr, 102(6), 1585-1594. PMID: 26561626
- Zacharski LR, et al (2008). Decreased cancer risk after iron reduction in patients with peripheral arterial disease: results from a randomized trial. J Natl Cancer Inst, 100(14), 996-1002. PMID: 18612130
- Adams PC, et al (2005). Hemochromatosis and iron-overload screening in a racially diverse population. N Engl J Med, 352(17), 1769-1778. PMID: 15858186
- Rushton DH, Barth JH (2010). What is the evidence for gender differences in ferritin and haemoglobin?. Crit Rev Oncol Hematol, 73(1), 1-9. PMID: 19394859
- Krayenbuehl PA, et al (2011). Intravenous iron for the treatment of fatigue in nonanemic, premenopausal women with low serum ferritin concentration. Blood, 118(12), 3222-3227. PMID: 21705493
- Galaris D, et al (2019). Iron homeostasis and oxidative stress: An intimate relationship. Biochim Biophys Acta Mol Cell Res, 1866(12), 118535. PMID: 31446062
Medical Disclaimer
This article is for educational purposes only and does not constitute medical advice. Iron supplementation should be guided by testing — both ferritin AND CRP. Excessive iron is harmful; do not supplement without confirming deficiency. Those with hemochromatosis or iron-loading conditions should work closely with a healthcare provider.