Beta-2-microglobulin
A small protein on the surface of most cells that is shed into the blood and cleared by the kidneys. Its main use is in blood cancers, especially multiple myeloma, where the level helps stage the disease and predict outcome — though kidney impairment also raises it.
What it measures
Beta-2-microglobulin is a small protein found on the surface of nearly all cells, particularly white blood cells. It is continuously shed into the blood, filtered by the kidneys and reabsorbed, so its blood level reflects two things: how many cells are producing and turning it over, and how well the kidneys are clearing it. Its established clinical role is in certain blood cancers. In multiple myeloma (a cancer of plasma cells), the beta-2-microglobulin level is a key part of staging and prognosis — higher levels indicate more advanced disease and a less favourable outlook, and it is tracked to monitor the disease and treatment. It is also used in some lymphomas. Because reduced kidney function raises it independently of any cancer, the level is always interpreted alongside kidney function (creatinine), so a high value isn't misread. It is a specialist marker, used within the care of these specific conditions rather than as a general test.
What a high value can mean
- Multiple myeloma — a key staging and prognostic marker; higher levels mean more advanced disease.
- Some lymphomas and other blood cancers.
- Reduced kidney function — raises it independently of cancer, so it is read with creatinine.
- Chronic inflammatory or infectious conditions — can raise it non-specifically.
What a low value can mean
- Normal or low — the expected result outside the specific conditions it is used for.
- A falling level during treatment of myeloma — can indicate a response.
When to discuss with a doctor
Beta-2-microglobulin is a specialist test, used mainly within the diagnosis, staging and monitoring of multiple myeloma and some lymphomas rather than as a general screen. In someone with myeloma, it contributes to working out the stage and likely course, and is followed to monitor the disease and its treatment, interpreted by haematology. Because kidney impairment raises it on its own, it is always read together with kidney function so a high level from the kidneys isn't mistaken for cancer activity. Mediora.AI shows beta-2-microglobulin alongside the relevant markers (immunoglobulins, kidney function, calcium) so it is read in context; the interpretation belongs with your specialist team.