Unit Converter
Albumin
Synonyms
- Albumin
- Serum Albumin
- Human Serum Albumin (HSA)
- Plasma Albumin
Units of Measurement
mmol/L, µmol/L, mcmol/L, umol/L, µM/L, mcM/L, uM/L, micromol/L,
g/L, g/dL, g/100mL, g%, mg/mL
Description
Albumin is the most abundant plasma protein in human blood, forming about 55–60% of total plasma protein.
It is synthesized in the liver at a rate of ~10–15 g/day.
Albumin plays essential roles in:
- Maintaining oncotic pressure (prevents edema)
- Transporting substances (bilirubin, hormones, calcium, fatty acids, drugs)
- Antioxidant function (free thiol group scavenges reactive species)
- Buffering blood pH
- Drug binding (warfarin, phenytoin, valproate)
Albumin levels are sensitive indicators of liver function, nutritional status, inflammation, and critical illness.
Physiological Role
1. Oncotic Pressure
Albumin provides ~75% of plasma oncotic pressure.
Low albumin → edema, ascites, pleural effusion.
2. Transport Functions
Binds:
- Calcium
- Bilirubin
- Thyroid hormones
- Steroid hormones
- Free fatty acids
- Medications
- Heavy metals
3. Acid–Base Balance
Acts as a major plasma buffer.
4. Antioxidant
Reduces oxidative stress via free thiol (Cys-34) group.
Clinical Significance
Elevated Albumin
Usually indicates:
- Dehydration
- Hemoconcentration
Rarely a true pathological increase.
Low Albumin (Hypoalbuminemia)
More clinically important.
A) Reduced Synthesis
- Liver cirrhosis
- Chronic hepatitis
- Severe malnutrition
- Inflammation (IL-6 suppresses synthesis)
- Protein-energy malnutrition
B) Increased Loss
- Nephrotic syndrome
- Protein-losing enteropathy
- Severe burns
- Exudative dermatoses
C) Dilutional
- Congestive heart failure
- Pregnancy
- IV fluid overload
D) Increased Catabolism
- Sepsis
- Trauma
- Malignancy
- Post-surgical states
Clinical Consequences
- Edema
- Low effective circulating volume
- Altered drug binding
- Higher risk in ICU patients
Reference Intervals
| Age Group | g/dL | g/L | µmol/L |
| 0–4 days | 2.8–4.4 | 28–44 | 421–662 |
| 4 days–14 years | 3.8–5.4 | 38–54 | 572–812 |
| 14–18 years | 3.2–4.5 | 32–45 | 481–677 |
| Adults (18–60 yrs) | 3.5–5.2 | 35–52 | 527–782 |
| 60–90 years | 3.2–4.6 | 32–46 | 481–692 |
| >90 years | 2.9–4.5 | 29–45 | 436–677 |
ESAP - Adult Chemistry Range:
3.5 – 5.0 g/dL (35 – 50 g/L)
Unit Meanings
| Unit | Meaning |
| mmol/L | millimole per liter |
| µmol/L | micromole per liter |
| mcmol/L | micromole (alternate form) |
| umol/L | micromole (alternate spelling) |
| µM/L | micromolar |
| mcM/L | micromolar (variant) |
| uM/L | micromolar |
| g/L | gram per liter |
| g/dL | gram per deciliter |
| g/100mL | equivalent to g% |
| g% | gram percent |
| mg/mL | milligram per milliliter |
Analytical Notes
- Measured using bromocresol green (BCG) or bromocresol purple (BCP) dye-binding methods.
- BCG may overestimate albumin in inflammatory states.
- BCP preferred for greater specificity.
- Hemolysis minimally affects the assay.
Clinical Pearls
- Albumin < 2.5 g/dL strongly predisposes to edema.
- Low albumin increases free (unbound) fraction of drugs → toxicity risk.
- Hypoalbuminemia predicts ICU mortality irrespective of disease.
- Sudden fall in albumin → think protein loss, not liver failure alone.
Interesting Fact
Albumin was first purified in 1894 and later used extensively in World War II as a plasma volume expander, saving thousands of lives.
References
- Tietz Clinical Chemistry and Molecular Diagnostics, 8th Edition - Plasma Proteins.
- ESAP 2024 - Chemistry Reference Ranges.
- Mayo Clinic Laboratories - Albumin Test Overview.
- IFCC Committee on Plasma Proteins.
- NIH / MedlinePlus - Serum Albumin Information.
- Rothschild MA. “Albumin metabolism and function.”
- Clinical Chemistry Reviews - Albumin and critical illness outcomes.