Unit Converter
Iron (Fe)
Synonyms
- Serum iron
- Plasma iron
- Fe
- Total iron concentration
- Circulating iron
Units of Measurement
- mmol/L
- µmol/L
- µg/dL
- µg/100 mL
- µg%
- µg/L
- ng/mL
Key Conversions
1 µmol/L = 55.85 µg/L
1 µg/L = 0.0179 µmol/L
1 µg/dL = 10 µg/L
1 µg/dL = 0.179 µmol/L
1 ng/mL = 1 µg/L
µg/100 mL = µg/dL = µg%
mmol/L Conversion
1 mmol/L=1000 µmol/L1\ \text{mmol/L} = 1000\ \text{µmol/L}1 mmol/L=1000 µmol/L
Description
Iron (Fe) is an essential trace element required for:
- Hemoglobin and myoglobin synthesis
- Oxidative metabolism (cytochromes)
- DNA synthesis
- Mitochondrial energy production
Serum iron reflects the amount of circulating iron bound to transferrin.
It does not measure total body stores (ferritin does that) but is essential for diagnosing iron metabolism disorders.
Physiological Role
1. Oxygen Transport
~70% of iron is in hemoglobin.
2. Muscle Function
Myoglobin stores oxygen in muscle.
3. Cellular Energy
Iron is a cofactor for:
- Cytochrome enzymes
- Electron transport chain
4. Immune & Neurological Function
Iron is important for:
- Neurotransmitter synthesis
- Immune cell proliferation
5. Iron Storage & Transport
Stored as:
- Ferritin (primary)
- Hemosiderin
Transported by:
- Transferrin
Clinical Significance
LOW Iron Levels (Iron Deficiency)
1. Iron Deficiency Anemia (IDA)
Causes include:
- Poor dietary intake
- Blood loss (GI bleeding, menstruation)
- Malabsorption (celiac disease, H. pylori)
- Increased requirements (pregnancy, growth spurts)
2. Chronic Inflammation
Functional iron deficiency:
- Low serum iron
- Normal/high ferritin
- Low TIBC
Seen in: - Chronic infection
- Autoimmune diseases
- CKD
- Cancer
3. Pregnancy
Increased iron demand → decreased circulating iron.
4. Malnutrition / Vegetarian Diets
HIGH Iron Levels
1. Hemochromatosis
- Hereditary HFE mutations (C282Y, H63D)
- Elevated iron, transferrin saturation, ferritin
2. Iron Overload
- Repeated transfusions (e.g., thalassemia major)
- Sideroblastic anemia
- Ineffective erythropoiesis
3. Liver Diseases
- Alcoholic liver disease
- Hepatitis
- Cirrhosis
4. Hemolysis
Release of RBC iron into serum.
5. Iron Poisoning
Acute ingestion → markedly elevated serum iron.
Reference Intervals
Adults
| Group | Serum Iron |
| Men | 65 – 180 µg/dL (11.6–32.2 µmol/L) |
| Women | 50 – 170 µg/dL (9.0–30.4 µmol/L) |
Children
- 50 – 120 µg/dL (9–21 µmol/L)
Pregnancy
- Lower values common
- Iron deficiency prevalent without supplementation
Critical Values
- Severe deficiency: <30 µg/dL
- Possible overload/toxicity: >300–500 µg/dL
Diagnostic Uses
1. Evaluate Iron Deficiency
Always interpreted with:
- Ferritin (stores)
- TIBC (transferrin)
- Transferrin saturation
2. Assess Iron Overload
- Hemochromatosis
- Transfusional overload
- Chronic liver disease
3. Monitor Iron Therapy
Response to oral or IV iron.
4. Evaluate Hemolysis
Iron may rise with RBC breakdown.
5. Workup of Anemia
Differentiate:
- IDA
- Anemia of chronic disease
- Sideroblastic anemia
6. Suspected Iron Poisoning
High serum iron within 2–4 hours of ingestion.
Analytical Notes
- Morning fasting sample preferred (diurnal variation → highest in morning).
- Hemolysis falsely elevates iron.
- Iron-binding tubes or contamination may alter results.
- Interpret only with TIBC, ferritin, and transferrin saturation.
- Ferritin is the earliest marker of iron deficiency.
Clinical Pearls
- Low iron + low ferritin = true iron deficiency.
- Low iron + normal/high ferritin = anemia of chronic inflammation.
- Transferrin saturation >45% strongly suggests hemochromatosis.
- Oral iron should not be taken 24 hours before test.
- Vitamin C increases iron absorption → may mildly increase levels.
Interesting Fact
The human body contains ~3–4 grams of iron, but only ~3 mg is absorbed daily, tightly regulated by the hormone hepcidin.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Iron Metabolism.
- WHO Guidelines - Iron Deficiency & Anemia.
- BSG/ACG Guidelines - Iron Deficiency Anemia Evaluation.
- Mayo Clinic Laboratories - Iron Panel.
- ARUP Consult - Iron Studies Interpretation.
- NIH / MedlinePlus - Iron Test.