Serum Albumin
Also known as: Serum albumin, Plasma albumin
Albumin is the most abundant plasma protein, made exclusively by the liver. It maintains oncotic pressure (keeping fluid in blood vessels) and transports hormones, drugs, and fatty acids. Low albumin is one of medicine's most informative and under-appreciated findings.
Venous blood (serum separator tube)
2–4 hours
Not required
Liver Function
Reference Ranges
| Measurement | Reference Range | Unit |
|---|---|---|
| Adults | 3.4 – 5.4 | g/dL |
Reference ranges are typical adult values. Your laboratory may use slightly different intervals — always use your lab's reported reference.
What This Test Measures
The liver produces 12–25 grams of albumin daily. With a half-life of 17–26 days, serum albumin reflects synthetic function over the past 2–4 weeks — it is an excellent marker of chronic liver disease and nutritional status, but too slow-changing to detect acute liver failure (where prothrombin time is better). Albumin's negative charge attracts positively charged molecules, making it the principal carrier for calcium, thyroid hormones, bilirubin, and many drugs.
When Is This Test Ordered?
- Liver disease evaluation and staging (Child-Pugh score uses albumin)
- Nutritional assessment in hospitalised patients
- Nephrotic syndrome investigation (massive protein loss lowers albumin)
- Interpreting calcium levels (albumin-corrected calcium adjusts for low albumin)
- Monitoring chronic illness and critical illness severity
When Results Are High
Slightly elevated albumin is almost always dehydration — a concentrated plasma with less water. Values above 5.5 g/dL are uncommon and usually artefactual.
When Results Are Low
Hypoalbuminaemia below 3.4 g/dL is a marker of severity across many conditions: advanced cirrhosis, nephrotic syndrome, protein-losing enteropathy, severe malnutrition, or critical illness. It causes oedema, ascites, and affects drug dosing (more free drug circulates when albumin is low). Below 2.5 g/dL is associated with significantly higher morbidity and mortality.
Factors That Can Affect Your Result
- Albumin is an acute-phase reactant in reverse — inflammation lowers it (negative acute phase protein)
- Pregnancy lowers albumin by ~0.5 g/dL through dilution
- Overhydration lowers albumin by dilution — IV fluids in hospitalised patients routinely drop albumin
- Posture matters — upright position concentrates albumin by ~10% vs supine
- Many drugs compete with albumin binding, changing drug distribution
Tracking This Test Over Time
Always correct serum calcium for albumin: corrected calcium (mg/dL) = measured calcium + 0.8 × (4 – albumin in g/dL). A calcium of 8.2 mg/dL with albumin of 2.0 g/dL gives a corrected calcium of 9.8 mg/dL — actually normal. Missing this correction leads to misdiagnosis of hypocalcaemia in hypoalbuminaemic patients.
Track your Albumin in LoomsRelated Tests
ALT
ALT is the most liver-specific enzyme in the standard panel. When liver cells are damaged, they release ALT into the bloodstream, making it a sensitive early warning for hepatitis, fatty liver disease, and medication toxicity.
PT / INR
Prothrombin time measures how long blood takes to form a clot via the extrinsic coagulation pathway. The INR standardises PT results across laboratories and is essential for monitoring warfarin therapy.
Bilirubin
Bilirubin is the yellow pigment produced when red blood cells are broken down. High bilirubin causes jaundice and signals problems with red cell destruction, liver processing, or bile duct drainage.
Calcium
Calcium is tightly regulated by PTH, vitamin D, and calcitonin. Abnormal calcium — whether high or low — can cause symptoms ranging from muscle cramps to kidney stones to cardiac arrhythmias.
Medical disclaimer
This page is for educational purposes only and does not constitute medical advice. Reference ranges vary between laboratories, and results must be interpreted in the context of your symptoms, history, and other tests. Always discuss your results with your healthcare provider. Content reviewed by the Looms medical team, 2026-06-01.