Albumin
The most abundant protein in blood, made by the liver.
Albumin is the most abundant protein in blood plasma, made by the liver. It holds fluid inside blood vessels by exerting osmotic pressure, and it acts as a transport vehicle for hormones, fatty acids, calcium, bilirubin and a great many drugs.
It appears on almost every routine blood panel, and its value there is as a general indicator rather than a specific one. A low albumin says something is wrong without saying what, which is both its limitation and the reason clinicians pay attention to it.
Low levels have several distinct causes. The liver may not be making enough, in chronic liver disease. The kidneys may be losing it into urine, in nephrotic syndrome. It may be diluted by fluid overload. It falls during inflammation and acute illness, because the liver reprioritises what it produces. And prolonged undernutrition lowers it, though more slowly and less specifically than the phrase nutritional marker suggests.
That inflammatory behaviour is the most commonly missed point. Albumin is a negative acute phase reactant, so it drops during infection and after surgery in someone perfectly well nourished, and reading it as a protein intake score in that setting is simply wrong.
It also appears in biological age calculations, including the Phenotypic Age equation our calculator implements, where it contributes alongside eight other standard blood markers.
High albumin is usually just dehydration, which concentrates everything in the sample, and rarely means anything on its own.
In practice, read it in context with the rest of the panel, and treat a persistently low value as a question for a clinician rather than a reason to eat more protein.
Sources
Where your own result would sit
Most people reading this page are holding a blood-test report with this marker on it, and the question they arrived with is whether their number is normal. A reference interval says where most results from a healthy population fall; a guideline threshold is where a clinical body draws a line for a decision. Neither is a target, and a result on the wrong side of one is not a diagnosis: the same number can be unremarkable in one person and worth looking into in another, which is why the clinician who ordered the test reads it against your history rather than against a list.
Albumin has no published interval on this page yet. We hold one, and the dashboard draws it beside a reader’s own result, but it has not been read back against the laboratory’s own page since it was collected. A figure printed beside somebody’s blood result has to have been seen at its source, not remembered, so this one waits.
On your own blood test?
Albumin is one of the markers FitTools can read from an uploaded blood-test report. You confirm every value before anything is saved, and your results are explained together in one place.