Biomarker 101: Albumin

Albumin is the most abundant protein in your blood, and one of the quieter markers on a panel — it reflects liver function, kidney function and nutrition all at once.

What albumin is

Albumin is made by the liver and circulates in large quantities. It does two main jobs.

It keeps fluid inside blood vessels, exerting the osmotic pull that stops fluid leaking into surrounding tissue. And it transports things — hormones, fatty acids, vitamins, calcium and many medications travel bound to albumin.

That second role has a practical consequence for reading other results. Because a large share of blood calcium is bound to albumin, a low albumin will lower total calcium without the active fraction changing. Laboratories often report a corrected calcium for this reason. Albumin is also used in calculating free testosterone.

Why it's measured

Albumin appears in liver panels and general health screens. It is used when liver or kidney function is in question, when nutritional status is being assessed, and as an input to other calculations.

What the numbers mean

A typical adult reference range is around 35 to 50 g/L, varying between laboratories.

What moves albumin

Low albumin has a wide range of causes. Liver disease reduces production. Kidney conditions can cause protein to be lost in urine. Inflammation from any source — infection, burns, recent surgery — lowers it, sometimes substantially. Conditions affecting absorption in the gut, insufficient dietary protein, and advanced illness all contribute. Pregnancy lowers albumin through simple dilution as blood volume increases.

High albumin is much less common and usually reflects dehydration rather than anything about the protein itself. It can also result from a sample taken with a tourniquet left on too long — a collection artefact rather than a finding.

What albumin won't tell you

• It isn't specific. Low albumin narrows nothing on its own; it is read with liver enzymes, kidney markers and inflammatory markers.
• It isn't a nutrition score. Albumin falls with inflammation regardless of diet, so it is a poor standalone measure of nutritional status.
• It responds slowly. Albumin has a long half-life, so it reflects weeks rather than days.
• Don't self-treat it. Albumin supplements sold over the counter are not how low albumin is addressed; the underlying cause is what matters.

The bottom line

Albumin is a broad indicator rather than a specific one. On its own it says little; alongside liver enzymes, kidney markers and inflammatory markers, it helps complete the picture — and it quietly affects how several other results are interpreted.