Albumin
Albumin· also: Alb, Serum Albumin
Clinical Overview
Albumin is the most abundant protein in blood plasma, produced exclusively by the liver. It maintains oncotic pressure (keeping fluid in blood vessels), transports hormones, fatty acids, and drugs, and acts as a buffer. Albumin is a marker of liver synthetic function and nutritional status.
Why This Test Matters
Low albumin (hypoalbuminemia) is a marker of chronic liver disease, nephrotic syndrome (urinary albumin loss), malnutrition, or severe systemic illness. Because albumin has a half-life of ~20 days, it reflects chronic (not acute) changes in protein synthesis. Albumin is part of the Child-Pugh score for cirrhosis staging. Critically low albumin increases risk of tissue edema and drug toxicity (reduced protein binding alters drug distribution).
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 3.5 – 5 | g/dL | — |
Also reported in: g/L.
Critical (Panic) Values
Critical Low: < 2 g/dL. Values outside these limits require immediate clinical attention.
What Causes Abnormal Results?
High Albumin Causes
- Dehydration (relative hyperalbuminemia — not true excess)
Low Albumin Causes
- Liver disease (cirrhosis, hepatic failure) — reduced synthesis
- Nephrotic syndrome — urinary loss of albumin
- Malnutrition and protein-calorie deficiency
- Inflammatory states (acute phase reaction — albumin is negative acute phase protein)
- Burns (massive protein loss)
- Protein-losing enteropathy (GI loss)
- Chronic disease (cancer, heart failure, sepsis)
Signs & Symptoms to Watch For
How to Prepare for This Test
No special preparation. Albumin can be affected by posture (upright position raises albumin slightly due to fluid shift). Prolonged use of a tourniquet during blood draw raises albumin.
Factors That Can Affect Results
- Posture (standing raises albumin by ~5–10%)
- Prolonged tourniquet application (raises albumin)
- Inflammatory conditions (lower albumin as negative acute phase protein)
- Dilution from IV fluids
- Pregnancy (physiologically lower — plasma volume expansion)
Related Topics
Frequently Asked Questions
Why is albumin low in liver disease?
The liver is the only organ that produces albumin. In chronic liver disease (cirrhosis), the mass of functioning liver cells decreases, reducing albumin synthesis. Because albumin has a long half-life (~20 days), it reflects chronic rather than acute liver injury — a patient with acute hepatitis may have normal albumin even with very elevated ALT. Declining albumin in a cirrhotic patient signals worsening synthetic function.
What is corrected calcium and why is albumin needed to calculate it?
Approximately 40% of blood calcium is bound to albumin. When albumin is low, measured total calcium appears falsely low, even if ionized (free) calcium is normal. Corrected calcium = measured calcium (mg/dL) + 0.8 × (4.0 − albumin g/dL). This correction ensures accurate assessment of calcium status. Alternatively, ionized calcium can be measured directly.