Biochemistry · Topic
Serum albumin as a lab test !
Albumin is the most abundant plasma protein; it falls in liver, kidney and inflammatory disease and in malnutrition.
Updated 2026-11-01
Key facts
- It is made only in the liver; half-life about 3 weeks.
- It holds oncotic pressure and carries calcium, unconjugated bilirubin, fatty acids, hormones and many drugs.
- It is a negative acute-phase protein: inflammation cuts its synthesis, so it is a poor stand-alone marker of malnutrition.
- Corrected calcium = measured calcium + 0.8 × (4 − albumin in g/dL); measured ionised calcium is more reliable.
- In urine, the albumin/creatinine ratio detects early kidney damage (diabetic and hypertensive nephropathy).
In detail
- What it measures: serum albumin concentration (colorimetric method); the rest of total protein is globulins.
- Where it comes from: hepatocytes make it daily; synthesis falls with inflammation (IL-6, TNF-α) and liver failure.
- Why it falls: cirrhosis, nephrotic syndrome (urinary loss), protein-losing enteropathy, burns, sepsis and critical illness (capillary leak and inflammation), protein malnutrition (kwashiorkor), fluid overload.
- Why it rises: almost only with dehydration (haemoconcentration).
- Effects of hypoalbuminaemia: oedema and ascites, less drug bound (more free fraction, for example phenytoin), low total calcium with normal ionised calcium, a falsely low anion gap.
- Pitfalls: a sample taken with a prolonged tourniquet raises it; the normal value varies by method and laboratory.
- Also called
- Albumin, Albumin/globulin ratio, Albuminuria
Clinical notes
- Low albumin is a strong predictor of death in hospital patients, mainly because it reflects inflammation.
- Nutritional status is judged by combining it with history, weight and sometimes prealbumin, read alongside CRP.
- In cirrhosis, albumin is part of the Child–Pugh score and is used as a plasma expander in large-volume paracentesis and hepatorenal syndrome.
Related conditions
Related
- Liver function tests: reading the pattern
- Anion gap and delta ratio
- Calcium and phosphate
- Bilirubin
- C-reactive protein (CRP) as a lab test
Test yourself
Think of the answer, then tap the question to see it.
Why is albumin a poor stand-alone marker of malnutrition?
It is a negative acute-phase protein: inflammation and liver disease lower it even when protein intake is adequate.
How does hypoalbuminaemia affect total calcium?
It lowers it because less albumin carries calcium, but ionised calcium may be normal; so it is corrected or ionised calcium is measured.
Which urine test detects early diabetic nephropathy?
The albumin/creatinine ratio in a spot urine sample (moderately increased albuminuria).
Which formula corrects calcium for albumin?
Corrected calcium = measured calcium + 0.8 × (4 − albumin in g/dL).
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Albumin Blood Test: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Albumin blood (serum) test: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Total Protein and Albumin/Globulin (A/G) Ratio : MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Microalbumin Creatinine Ratio: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.