Ferritin

Storage form of iron

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Vitamins &NutrientsCategory

Men:24-336 ng/mL, WReference

Widely Available

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Reference Range

Men:24-336 ng/mL, Women:11-307 ng/mL, Optimal:50-150 ng/mL

What is Ferritin?

Ferritin is the primary storage form of iron in your body, found mainly in the liver, spleen, bone marrow, and muscles. Serum ferritin (measured in blood tests) reflects total body iron stores:low ferritin indicates iron deficiency, while high ferritin may indicate iron overload, inflammation, or chronic disease. Ferritin is a more sensitive marker of iron status than serum iron or hemoglobin—ferritin drops FIRST as iron stores deplete, long before anemia develops. This is why checking ferritin is essential for detecting early iron deficiency.

Here's the critical insight:"normal"ferritin ranges are far too broad (12-300 ng/mL for men, 12-150 ng/mL for women), and the lower limit is dangerously low. Ferritin <30 ng/mL causes fatigue, brain fog, hair loss, and restless legs even without anemia. For optimal energy, cognitive function, and athletic performance, functional medicine practitioners target ferritin >50 ng/mL (ideally 70-100 ng/mL). Women of childbearing age, vegetarians, athletes, and frequent blood donors are at highest risk of low ferritin.

Ferritin is also an acute-phase reactant—it rises during inflammation or infection, which can mask true iron deficiency. If you have both inflammation (elevated CRP) and low-normal ferritin (30-50 ng/mL), you may actually be iron deficient despite ferritin appearing "normal."In this case, check additional iron markers:serum iron, TIBC, transferrin saturation, and consider soluble transferrin receptor (sTfR).

Why Ferritin (Iron Stores) Matters for Longevity

Oxygen transport:Iron is the core of hemoglobin (carries oxygen in red blood cells) and myoglobin (stores oxygen in muscles). Low iron=less oxygen delivery=fatigue, weakness, shortness of breath.
Energy production:Iron is a cofactor for cytochrome enzymes in the mitochondrial electron transport chain. Low iron impairs ATP production, causing fatigue even without anemia.
Cognitive function:Iron is required for neurotransmitter synthesis (dopamine, serotonin, norepinephrine) and myelin formation. Low iron causes brain fog, poor concentration, depression, and impairs child cognitive development.
Thyroid function:Iron is required for thyroid peroxidase enzyme, which synthesizes thyroid hormones. Iron deficiency impairs T4→T3 conversion and can worsen hypothyroidism.
Immune function:Iron is required for immune cell proliferation and function. Both too little (impaired immunity) and too much (promotes bacterial growth) are problematic.
Physical performance:Low ferritin impairs exercise capacity, endurance, and muscle recovery. Athletes with ferritin <50 ng/mL have reduced performance.

Optimal vs Standard Ranges

Range Type	Level	Significance
Optimal (Longevity)	70-100 ng/mL	Target for optimal energy, cognitive function, athletic performance. Many functional medicine doctors target >70 ng/mL.
Adequate (Standard)	50-70 ng/mL	Sufficient to prevent symptoms in most people. May be suboptimal for athletes or those with high iron needs.
Suboptimal (Low-Normal)	30-50 ng/mL	Low-normal. May cause fatigue, hair loss, restless legs, reduced exercise capacity. Consider iron supplementation.
Iron Deficiency	<30 ng/mL	Iron deficiency without anemia. Causes fatigue, brain fog, hair loss, restless legs, cold intolerance. Supplement with iron.

Standard lab range: Men:24-336 ng/mL, Women:11-307 ng/mL, Optimal:50-150 ng/mL

How to Optimize Ferritin

1. Severe Deficiency

<12 ng/mL

2. Severe iron deficiency, often with anemia (low hemoglobin). Requires aggressive iron supplementation (oral or IV).

Elevated (Inflammation/Overload)

3. >300 ng/mL (men) or >200 ng/mL (women)

High ferritin may indicate:(1) Inflammation/infection (most common—check CRP), (2) Hemochromatosis (genetic iron overload), (3) Chronic disease (liver disease, cancer), (4) Excessive iron supplementation.

4. Iron Supplementation (Dose and Form)

Ferrous sulfate:325 mg (65 mg elemental iron) once or twice daily. Cheapest and most common form but causes GI side effects (nausea, constipation, black stools). Take on empty stomach with vitamin C (enhances absorption).

Ferrous bisglycinate (chelated iron):25-50 mg elemental iron daily. Gentler on stomach, better tolerated, higher bioavailability than sulfate. Preferred form for most people.

Iron polysaccharide:150 mg elemental iron daily. Non-ionic form, minimal GI side effects.

Timing:Take iron away from meals (or with low-phytate meals), away from calcium, tea, coffee (inhibit absorption). Pair with vitamin C (enhances absorption).

Duration:Expect 2-3 months to raise ferritin significantly. Retest after 3 months and adjust dose.

5. Dietary Sources of Iron (Heme vs Non-Heme)

Heme iron (animal sources, highly bioavailable, 15-35% absorbed):Red meat (beef, lamb), organ meats (liver), poultry, fish, shellfish (oysters, clams). Liver is extraordinarily high in iron (5-10 mg per 3 oz).

Non-heme iron (plant sources, poorly absorbed, 2-20% absorbed):Spinach, lentils, chickpeas, tofu, fortified cereals, dark chocolate. Absorption enhanced by vitamin C, impaired by phytates (grains, legumes), tannins (tea, coffee), calcium.

Vegetarians/vegans need 1.8x more iron due to lower bioavailability of plant iron. Consider iron supplementation if ferritin <50 ng/mL.

Symptoms of Abnormal Ferritin

Low Ferritin

Optimize Iron Absorption

High Ferritin

Treat Underlying Causes of Low Ferritin

Causes of Abnormal Ferritin

Low Levels

Evaluate Iron Overload if Ferritin Very High

High Levels

If ferritin >300 ng/mL (men) or >200 ng/mL (women) without supplementation:
Check CRP:If CRP elevated, high ferritin is likely inflammation, not iron overload.
Check transferrin saturation and serum iron:If transferrin saturation >45%, consider hemochromatosis.
Hemochromatosis genetic testing:HFE gene mutations (C282Y, H63D). If positive, requires phlebotomy (blood removal) to prevent iron-induced organ damage (liver cirrhosis, diabetes, heart failure).
Liver disease, cancer, chronic infection can also raise ferritin.

When to Retest

Fatigue, exhaustion, low energy (most common symptom)
Weakness, difficulty with physical exertion
Shortness of breath, especially with activity
Pale skin, pale conjunctiva (inner eyelids)
Cold intolerance, always feeling cold
Brain fog, poor concentration, memory problems
Headaches, dizziness
Hair loss, brittle nails
Restless leg syndrome (irresistible urge to move legs, worse at night)
Pica (craving non-food items like ice, dirt, starch)
Rapid heartbeat, palpitations (if anemic)
Decreased immune function, frequent infections
Impaired exercise performance, reduced endurance

Scientific Evidence

Low ferritin <30 ng/mL causes symptoms even without anemia. Severe deficiency <12 ng/mL often accompanied by anemia (low hemoglobin).

High ferritin (>300 ng/mL men, >200 ng/mL women) may indicate iron overload, inflammation, or chronic disease. Symptoms of iron overload (hemochromatosis):|Joint pain, especially knuckles|Fatigue, weakness|Abdominal pain|Loss of libido, erectile dysfunction|Bronze or gray skin discoloration|Diabetes (iron damages pancreas)|Liver disease, cirrhosis|Heart arrhythmias, heart failure (iron deposits in heart)|Increased infection risk (excess iron promotes bacterial growth)

Source:High ferritin from inflammation is most common (check CRP). True iron overload (hemochromatosis) is less common but serious.

Heavy menstrual bleeding:Most common cause in premenopausal women. Loses 30-50 mg iron per cycle if heavy.|Pregnancy and breastfeeding:Increased iron requirements (27 mg/day pregnant, 9-10 mg/day lactating). Fetus depletes maternal iron stores.|Vegetarian/vegan diet:Plant iron (non-heme) poorly absorbed (2-20%) vs meat iron (heme, 15-35%). Vegetarians need 1.8x more iron.|Frequent blood donation:Each donation removes ~200-250 mg iron, lowering ferritin by 20-30 ng/mL.|GI blood loss:Chronic NSAID use (aspirin, ibuprofen), ulcers, gastritis, inflammatory bowel disease, colon cancer, celiac disease.|Malabsorption:Celiac disease (most common), atrophic gastritis, H. pylori, gastric bypass, chronic diarrhea.|Intense endurance training:Athletes lose iron via foot-strike hemolysis, GI bleeding, sweat. "Sports anemia."|Rapid growth:Adolescents, especially girls, have increased iron needs.|Chronic kidney disease:Impaired erythropoietin production reduces iron utilization.

Hereditary hemochromatosis:Genetic disorder (HFE gene mutations C282Y, H63D) causing excessive iron absorption. Most common genetic disorder in Caucasians (1:200-300).|Excessive iron supplementation:Taking high-dose iron without deficiency.|Frequent blood transfusions:Chronic anemia (thalassemia, sickle cell) requiring transfusions leads to iron overload.|Chronic liver disease:Cirrhosis, hepatitis impair iron regulation and raise ferritin.|Inflammation or infection:Acute-phase reaction raises ferritin (check CRP to distinguish from true iron overload).|Cancer:Some cancers (liver, pancreatic, leukemia) raise ferritin.|Alcohol abuse:Damages liver, impairs iron regulation.

Source:Baseline:Check ferritin if symptoms (fatigue, hair loss, restless legs) or risk factors (heavy periods, vegetarian, frequent donor, athlete).|After starting iron supplementation:Retest in 3 months. Expect ferritin to rise 30-50 ng/mL with consistent supplementation. Adjust dose based on response. Goal:>50 ng/mL (ideally 70-100 ng/mL).|Once optimal ferritin reached:Retest every 6-12 months to maintain. May need maintenance dose (25-50 mg every other day) to prevent recurrence, especially if underlying cause persists.|If high ferritin (>300 men, >200 women):Check CRP, transferrin saturation, consider hemochromatosis testing. Retest in 3 months.|If unexplained low ferritin despite supplementation:Investigate for GI blood loss (endoscopy, colonoscopy) or malabsorption (celiac testing).

Iron Deficiency Prevalence

Iron deficiency is the most common nutritional deficiency worldwide, affecting 25-30% of the global population. In US, 10-15% of women of childbearing age are iron deficient (ferritin <30 ng/mL), and 5-10% have iron deficiency anemia. Vegetarians/vegans have 2-3x higher rates.

Source:WHO. Iron deficiency anemia:assessment, prevention and control. Geneva:World Health Organization, 2001.

Ferritin and Fatigue

Studies show ferritin <50 ng/mL is associated with fatigue even without anemia. Iron supplementation in non-anemic women with ferritin <50 ng/mL reduces fatigue by 50% within 3 months. Athletes with ferritin <35 ng/mL have impaired endurance and performance;supplementation improves VO2max and exercise capacity.

Source:Krayenbuehl PA, et al. Intravenous iron for the treatment of fatigue in nonanemic, premenopausal women with low serum ferritin concentration. Blood. 2011;118(12):3222-3227.

Ferritin and Restless Leg Syndrome

Low ferritin (<50 ng/mL) is a major cause of restless leg syndrome (RLS). Brain iron deficiency impairs dopamine synthesis. Iron supplementation (target ferritin >75 ng/mL) improves or resolves RLS in 60-70% of patients with low ferritin. IV iron more effective than oral for refractory RLS.

Source:Allen RP, et al. Evidence-based and consensus clinical practice guidelines for the iron treatment of restless legs syndrome. Sleep Med. 2018;41:27-44.

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