Iron (Serum)
Serum iron measures the iron currently bound to transferrin in blood and varies substantially during the day and with recent intake. It is interpreted together with TIBC, transferrin saturation, and ferritin to assess iron status. Low serum iron suggests deficiency or chronic disease, while high values can indicate iron overload, hemolysis, or recent supplementation.
Units: µg/dL; some labs report µmol/L (µmol/L = µg/dL × 0.179). Check the units on your report before comparing to any range here.
Optimal range: who says what
Institutions, researchers and practitioners draw the line in different places. Each position is listed with who holds it and, where a document states it, a link. How we verify ranges.
- Named practitioner40-100 μg/dL women / 50-100 menLife Extension · Lab Testing Protocol (Suggested Optimal Ranges)Disclosure: Life Extension sells lab panels that appear in our blood-test comparisons.
- Lab reference intervalMen: 65-175 μg/dL, Women: 50-170 μg/dLWhat a lab report flags against. A lab interval is not an optimal target.
Practitioner targets are individual positions, often tighter than guideline ranges. Each was checked against its article before publishing.
16 of 21 itemized panels
Vitamins & Nutrients
What is Iron (Serum)?
Serum iron measures the amount of iron currently circulating in your bloodstream, bound to transferrin (the iron transport protein). Unlike ferritin (which reflects iron stores), serum iron reflects the iron available for immediate use by cells. Serum iron fluctuates significantly throughout the day and is influenced by recent meals, inflammation, and diurnal variation (highest in morning, lowest at night). Because of this variability, serum iron alone is not a reliable marker of iron status—it must be interpreted alongside ferritin, TIBC (total iron-binding capacity), and transferrin saturation.
Serum iron, TIBC, and transferrin saturation work together to paint a complete picture of iron status. Low serum iron + high TIBC + low transferrin saturation = iron deficiency (body desperately trying to capture more iron). High serum iron + low TIBC + high transferrin saturation (>45%) = iron overload (hemochromatosis). Normal serum iron + low TIBC = anemia of chronic disease (inflammation sequesters iron). You can't interpret serum iron in isolation—you need the full iron panel.
Transferrin saturation is the most useful calculated value: (Serum Iron / TIBC) × 100. Normal is 20-45%. <20% indicates iron deficiency; >45% suggests iron overload. Transferrin saturation <20% with ferritin <30 ng/mL confirms iron deficiency anemia. Transferrin saturation >45% with ferritin >300 ng/mL (men) or >200 ng/mL (women) suggests hemochromatosis—genetic testing for HFE mutations is warranted.
Why Serum Iron Matters (As Part of Full Iron Panel)
- Diagnose iron deficiency vs anemia of chronic disease: Low serum iron can be due to true iron deficiency OR inflammation. TIBC and ferritin differentiate: iron deficiency (high TIBC, low ferritin) vs chronic disease (low TIBC, normal/high ferritin).
- Detect iron overload (hemochromatosis): High serum iron + high transferrin saturation (>45%) indicates excessive iron absorption. Hemochromatosis causes cirrhosis, diabetes, heart failure if untreated.
- Guide iron supplementation: If transferrin saturation <20% and ferritin <30 ng/mL, iron supplementation is clearly indicated. Monitor transferrin saturation and ferritin to track response.
- Evaluate unexplained fatigue or anemia: Serum iron (with TIBC, ferritin, transferrin saturation) identifies the cause: iron deficiency, chronic disease, hemochromatosis, or other.
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: Iron deficiency anaemia revisited (Cappellini et al., 2020); New insights into iron deficiency and iron deficiency anemia (Camaschella, 2017). No single paper sets these cutoffs; for attributed targets see who says what.
Optimal (with TIBC and Transferrin Saturation)60-170 mcg/dL (men) 50-150 mcg/dL (women)▼
- Normal range for serum iron
- Must interpret with TIBC and transferrin saturation (optimal 25-35%)
Low Serum Iron<50 mcg/dL▼
- Low serum iron
- Check TIBC and ferritin
- If TIBC high (>400) + ferritin low (<30) = iron deficiency
- If TIBC low (<250) + ferritin normal/high = anemia of chronic disease (inflammation)
High Serum Iron>200 mcg/dL▼
- High serum iron
- Check TIBC and transferrin saturation
- If transferrin saturation >45% + ferritin >300 (men) or >200 (women) = possible hemochromatosis
- If acute, may be from recent iron supplementation, blood transfusion, or hemolysis
Low Transferrin Saturation<20%▼
- Iron deficiency
- Body can't saturate transferrin with iron
- Supplement with iron (ferrous bisglycinate 25-50 mg daily)
What raises or lowers Iron
Causes of high Iron
- Hereditary hemochromatosis: HFE gene mutations (C282Y, H63D) cause excessive iron absorption from diet. Most common genetic disorder in Caucasians (1:200-300).
- Frequent blood transfusions: Chronic anemia (thalassemia, sickle cell) requiring transfusions → iron overload.
- Excessive iron supplementation: Taking high-dose iron without deficiency.
- Acute iron ingestion: Iron poisoning (accidental or intentional overdose).
- Hemolysis: Red blood cell destruction releases iron into bloodstream (hemolytic anemia, transfusion reaction).
- Acute hepatitis or liver necrosis: Damaged hepatocytes release stored iron.
Causes of low Iron
- True iron deficiency: Low dietary iron (vegetarian/vegan), heavy menstrual bleeding, GI blood loss, malabsorption (celiac, gastric bypass).
- Anemia of chronic disease: Chronic infections (TB, HIV), autoimmune diseases (rheumatoid arthritis, lupus), cancer, chronic kidney disease. Inflammation (high CRP, IL-6) causes hepcidin release, which sequesters iron in macrophages, lowering serum iron.
- Pregnancy: Increased iron demand lowers serum iron and ferritin.
- Recent blood donation: Acutely lowers serum iron and ferritin.
Symptoms when Iron is high or low
When high
High serum iron with transferrin saturation >45% may indicate hemochromatosis:
- Joint pain, especially knuckles (iron deposits in joints)
- Fatigue, weakness
- Abdominal pain, liver enlargement
- Loss of libido, erectile dysfunction
- Bronze or gray skin discoloration
- Diabetes (iron damages pancreas)
- Cirrhosis, liver cancer
- Heart arrhythmias, cardiomyopathy
- Arthritis, especially hands
High serum iron + high transferrin saturation (>45%) suggests iron overload (hemochromatosis). Requires genetic testing and treatment.
When low
Low serum iron causes same symptoms as iron deficiency (see Ferritin section):
- Fatigue, weakness, low energy
- Shortness of breath, especially with activity
- Pale skin, pale conjunctiva
- Cold intolerance
- Brain fog, poor concentration
- Headaches, dizziness
- Hair loss, brittle nails
- Restless leg syndrome
- Pica (craving ice, dirt, starch)
Low serum iron with high TIBC and low ferritin = iron deficiency. Low serum iron with low TIBC and normal/high ferritin = anemia of chronic disease.
How to move Iron
Effect sizes (how much something moves the marker) appear only where the paper cited under the item states them. Talk to your clinician before starting or changing any medication or supplement.
Correct Iron Deficiency (if transferrin saturation <20%)
- Serum iron <50 mcg/dL + TIBC >400 + transferrin saturation <20% + ferritin <30 ng/mL = iron deficiency anemia.
- Iron supplementation: Ferrous bisglycinate 25-50 mg elemental iron daily (or ferrous sulfate 325 mg once-twice daily). Take with vitamin C, away from calcium/tea/coffee.
- Dietary iron: Red meat, organ meats, shellfish (heme iron, highly bioavailable). Vegetarians need more dietary iron because non-heme iron is absorbed less well.
- Retest in 3 months: Ferritin and transferrin saturation should be rising; if not, look for ongoing loss or poor absorption.
Differentiate Iron Deficiency from Anemia of Chronic Disease
Both cause low serum iron and anemia, but iron studies distinguish them:
- Iron deficiency: Low serum iron, HIGH TIBC (>400), low transferrin saturation (<20%), LOW ferritin (<30). Treat with iron.
- Anemia of chronic disease: Low serum iron, LOW TIBC (<250), low-normal transferrin saturation (15-30%), NORMAL or HIGH ferritin (>100). Caused by inflammation (infections, autoimmune disease, cancer) sequestering iron. Treat underlying disease, NOT iron supplementation (can worsen inflammation).
Evaluate for Hemochromatosis (if transferrin saturation >45%)
- High serum iron + high transferrin saturation (>45%) + high ferritin (>300 men, >200 women) = possible hemochromatosis.
- HFE genetic testing: C282Y and H63D mutations. C282Y homozygous = hereditary hemochromatosis (most common).
- Phlebotomy: Treatment for hemochromatosis. Remove blood every 1-2 weeks until ferritin reaches the target your hematologist sets, then maintenance phlebotomy every 2-3 months.
- Untreated hemochromatosis causes cirrhosis, diabetes, cardiomyopathy, arthritis, bronze skin, erectile dysfunction.
Timing of Test (Morning Fasting)
- Serum iron has significant diurnal variation: Highest in morning (8-10 AM), lowest at night. Test fasting in the morning for accurate baseline.
- Avoid iron supplements for 24 hours before test (can falsely elevate serum iron).
Retest After Treatment
- If treating iron deficiency: Retest serum iron, TIBC, transferrin saturation, ferritin after 3 months of supplementation. Ferritin and transferrin saturation should be back in the normal range.
- If treating hemochromatosis: Monitor ferritin and transferrin saturation every 3 months during phlebotomy, then every 6-12 months for maintenance.
When to retest
- Baseline: Order full iron panel (serum iron, TIBC, transferrin saturation, ferritin) if anemia, fatigue, or risk factors for iron deficiency/overload.
- Always test in morning, fasting: Serum iron varies by time of day and recent meals.
- If low transferrin saturation (<20%) + low ferritin (<30): Confirms iron deficiency. Start iron supplementation, retest in 3 months.
- If high transferrin saturation (>45%) + high ferritin (>300 men, >200 women): Evaluate for hemochromatosis. Order HFE genetic testing.
- If low serum iron but normal/high ferritin: Consider anemia of chronic disease. Check CRP, ESR to assess inflammation.
- Retest after 3 months of iron supplementation: Ferritin should be rising and transferrin saturation moving into the normal range.
Scientific Evidence
Ferritin Outperforms Other Iron Tests
A systematic overview of 55 studies that used bone marrow examination as the reference standard found serum ferritin was by far the most powerful test for iron-deficiency anemia (area under the ROC curve 0.95). Interpretation differs in people with inflammatory, liver, or neoplastic disease.
Source: Laboratory diagnosis of iron-deficiency anemia: an overview.
Anemia of Chronic Disease Versus Iron Deficiency
Weiss and Goodnough review anemia of chronic disease, which accompanies infection, autoimmune disease, and cancer. Inflammation raises hepcidin, which traps iron in macrophages, so serum iron falls while ferritin stays normal or high. In iron deficiency, serum iron and ferritin are both low and TIBC is high.
Source: Anemia of chronic disease.
Hemochromatosis Diagnosis and Treatment
The AASLD practice guideline covers diagnosis and management of hereditary hemochromatosis: raised transferrin saturation and ferritin prompt HFE genetic testing, C282Y homozygosity is the most common genotype, and treatment is regular phlebotomy to reduce iron stores.
Which Providers Test Iron (Serum)?
Cheapest: Empirical Health at $190/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
16 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $190 | 100+ | $1.90 | |
| $297 | 100+ | $2.97 | |
 Superpower | $349 | 100+ | $3.49 |
| $349 | 75+ | $4.65 | |
 WHOOP Advanced Labs | $349 | 65 | $5.37 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $375 | 108 | $3.47 | |
| $495 | 80+ | $6.19 | |
| $499 | 100+ | $4.99 | |
| $700 | 138 | $5.07 | |
| $829 | 54 | $15.35 | |
| $895 | 100+ | $8.95 | |
| $996 | 59 | $16.88 | |
| $1188 | 70+ | $16.97 | |
| $1950 | 130+ | $15.00 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
5 itemized panels do not include Iron (Serum)
Labcorp OnDemand · Life Extension Elite · Everlywell · Marek Health Base · Oura Health Panels
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Iron (Serum). Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Iron (Serum)
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
Frequently Asked Questions
What is the optimal range for Iron (Serum)?
Named practitioners target: 40-100 μg/dL women / 50-100 men (Life Extension). Lab reference interval: Men: 65-175 μg/dL, Women: 50-170 μg/dL. That is what a lab report flags against, not an optimal target.
Which blood test providers include Iron (Serum)?
16 of the 21 blood testing panels we itemize marker by marker include Iron (Serum) in their panels. This biomarker is widely available across major providers.
Related: YouBoost rates lifestyle and supplement interventions by evidence.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed Sep 23, 2026 · First published Sep 30, 2025