albumin
Meaning of albumin: Often read as a nutrition marker, the level falls just as readily with inflammation, liver disease or loss through the kidneys.
Definition of albumin
Albumin is the most abundant protein in blood plasma, made by the liver. It holds fluid inside the blood vessels by exerting an inward pull across the vessel wall, and it ferries poorly soluble cargo through the circulation, including calcium, bilirubin, fatty acids, hormones and many drugs. The name also covers similar proteins found elsewhere, such as egg white.
What does it actually do?
Two things, and both matter more than they sound. Water follows dissolved protein, so the albumin packed into plasma exerts a steady inward pull that keeps fluid within the vessels rather than seeping into surrounding tissue. When the level drops far enough, that balance tips and fluid collects in the ankles, the abdomen or the lungs. Its other job is transport. Substances that do not dissolve well in water travel through the circulation stuck to albumin, and only the unbound fraction is active, so the amount of albumin available changes how much of a tightly bound drug is free to work. The same binding explains a familiar laboratory trap: a measured calcium level falls when albumin is low, without the active calcium having changed at all, which is why the two results are read together.
Why does the level fall?
| Route | Examples |
|---|---|
| Less is made | Liver disease, prolonged undernutrition |
| More is lost | Kidney disease leaking protein into urine, protein losing bowel conditions, extensive burns |
| Diluted or shifted | Fluid overload, and leaky capillaries in serious illness letting albumin escape into tissue |
| Production suppressed | Inflammation from any cause, which turns liver output toward other proteins |
Is it a good measure of nutrition?
Less than its reputation suggests. Albumin survives in the blood for around three weeks, so the level responds slowly and cannot reflect what someone ate recently. More importantly, inflammation suppresses its production directly: during infection, injury or major surgery the liver switches its effort toward other proteins and albumin falls whatever the diet. A low result in an acutely unwell person therefore signals the severity of the illness rather than a food shortage. It does predict poorer outcomes reliably, which is part of why the misreading persists, but the prediction comes from what the low level indicates about the underlying illness rather than from any shortage of the protein itself.
Also known as
Used in a sentence
The metabolic panel included an albumin level as part of the evaluation of the patient's nutritional and liver status.
Good to know
A low albumin level can reflect reduced production, increased loss through the kidneys or gut, dilution, or inflammation suppressing production regardless of food intake, so the level alone is an unreliable measure of nutrition.
Word origin
Where “albumin” comes from
From Latin albus, meaning white, referring to egg white, where the protein was first identified.