Albumin
Also reported as: Serum albumin
The most abundant protein in blood, made by the liver. It maintains oncotic pressure and carries hormones, drugs and fatty acids.
Wide, and the lower half of it is associated with meaningfully worse outcomes.
Mortality risk falls continuously across the reference range, so the top of it is the target rather than merely being inside it.
To convert to g/L, multiply by 10.
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Where the thresholds sit
| Band | Range (g/dL) | Note |
|---|---|---|
| Low | < 3.5 | Investigate liver disease, kidney loss, malnutrition or chronic inflammation. |
| Below optimal | 3.5–4.3 | — |
| Optimal | 4.3–5 | — |
| High | > 5 | Almost always dehydration rather than anything meaningful. |
Why it matters
One of the most underrated numbers on a routine panel. Albumin is a composite readout of liver synthetic function, nutritional status and chronic inflammation, and it predicts all-cause mortality strikingly well — it is a component of the PhenoAge biological age clock for exactly that reason. Within the normal range, higher is consistently better.
What raises it
- Dehydration, which concentrates it
- Adequate protein intake
What lowers it
- Chronic inflammation — albumin is a negative acute-phase reactant
- Liver disease
- Protein loss through the kidneys or gut
- Inadequate protein intake
- Overhydration at the time of the draw
How to move it
- 1Treat a low albumin as a question rather than a target. It is a symptom of something else, and raising it directly is not a thing you can do.
- 2Check hs-CRP alongside it. Low albumin with raised CRP points at inflammation rather than nutrition.
- 3Ensure adequate protein — roughly 1.2-1.6 g per kg for most active adults, more with age.
- 4If it is persistently below 3.5 with no obvious cause, that warrants medical investigation, not a supplement.
What moves this marker
Interventions on this site with evidence behind them for this specific marker. None of them replaces working out why yours is where it is.
What makes a single reading misleading
- Hydration status shifts it in both directions, so a single value can mislead.
- It falls in any inflammatory state independent of nutrition or liver function.
- It has a long half-life of around 20 days, so it reflects the previous few weeks rather than today.
Sources
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Educational only. Reference ranges are not diagnostic thresholds and this page cannot account for your medical history, medication or symptoms. Discuss any result that concerns you with a qualified clinician. See our medical disclaimer.