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[Biochemistry](https://durgical.com/en/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

- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Hypocalcaemia](https://durgical.com/en/conditions/hypocalcaemia/)
- [Refeeding syndrome](https://durgical.com/en/conditions/refeeding-syndrome/)
- [Crohn disease](https://durgical.com/en/conditions/crohn-disease/)

## Related

- [Liver function tests: reading the pattern](https://durgical.com/en/biochemistry/topics/liver-function-tests-reading-the-pattern/)
- [Anion gap and delta ratio](https://durgical.com/en/biochemistry/topics/anion-gap-and-delta-ratio/)
- [Calcium and phosphate](https://durgical.com/en/biochemistry/topics/calcium-and-phosphate/)
- [Bilirubin](https://durgical.com/en/biochemistry/molecules/bilirubin/)
- [C-reactive protein (CRP) as a lab test](https://durgical.com/en/biochemistry/topics/c-reactive-protein-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).

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Albumin Blood Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/albumin-blood-test/) (MedlinePlus, US National Library of Medicine, 2026); [Albumin blood (serum) test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003480.htm) (MedlinePlus, US National Library of Medicine, 2026); [Total Protein and Albumin/Globulin (A/G) Ratio: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/total-protein-and-albumin-globulin-a-g-ratio/) (MedlinePlus, US National Library of Medicine, 2026); [Microalbumin Creatinine Ratio: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/microalbumin-creatinine-ratio/) (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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