Beta-2 Microglobulin (β2-M)
Beta-2 microglobulin is a small protein present on the surface of nearly all nucleated cells. It is shed into blood continuously and cleared by the kidneys. Elevated β2-M reflects either increased cell turnover (lymphoma, multiple myeloma, chronic infection) or reduced renal clearance. In multiple myeloma, β2-M is part of the International Staging System and is a powerful prognostic marker. It is also used in lymphoma, HIV, and sometimes in kidney disease.
Reference Ranges
Male
0 – 2.5
mg/L
Female
0 – 2.5
mg/L
Child
Consult pediatrician
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low β2-microglobulin has no clinical significance. It is normal or even desirable. In follow-up of a patient previously treated for myeloma, falling β2-M suggests disease control or remission.
What High Levels Mean
Elevated β2-M in a patient with multiple myeloma places them in a higher-risk stage and predicts shorter survival — even when other markers look stable. Elevated β2-M in lymphoma also carries prognostic weight. In non-malignant contexts, it rises with kidney dysfunction (reduced clearance), chronic viral infections (HIV, CMV), autoimmune disease (SLE, rheumatoid arthritis), and acute inflammation.
Frequently Asked Questions
Is β2-microglobulin specific for cancer?
No. It rises in many conditions — kidney disease, chronic infection, autoimmune disease, and several cancers. Its value is not as a diagnostic marker but as a prognostic one once a specific disease (myeloma, lymphoma) is known. It is interpreted alongside kidney function — a rise in β2-M with worsening eGFR is often renal, not cancer.
How is β2-M used in myeloma staging?
The International Staging System (ISS) uses β2-M plus albumin: Stage I — β2-M <3.5 mg/L and albumin >3.5 g/dL; Stage II — neither I nor III; Stage III — β2-M >5.5 mg/L. Median survival differs substantially between stages. Revised ISS (R-ISS) also incorporates LDH and high-risk cytogenetics for more precise prognosis.
Why does kidney function affect β2-M?
β2-M is small enough to be freely filtered by the kidneys, then reabsorbed by the proximal tubules. In chronic kidney disease, filtration is reduced and β2-M rises. In tubular dysfunction (heavy metal toxicity, tubulointerstitial disease), urinary β2-M rises due to failed reabsorption. Interpreting serum β2-M therefore requires parallel knowledge of renal function.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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