The main reasons for high β2 microglobulin are decreased glomerular filtration rate, connective tissue disease or malignant tumor, rejection of kidney transplant patients. β2 microglobulin is a small molecular weight protein, which can also be considered as a kind of toxin. If a patient has renal failure and the detoxification ability of the kidneys decreases, the β2 microglobulin in the blood will be elevated. Therefore, this protein is often used to assess whether the kidney function is damaged. β2 microglobulin is mainly synthesized by lymphocytes and tumor cells, so if you suffer from connective tissue diseases, such as systemic lupus erythematosus, rheumatoid arthritis and so on, or malignant tumors, the synthesis of β2 microglobulin will increase, and the β2 microglobulin in the blood will be elevated. In addition, in the rejection reaction of kidney transplantation, the function of lymphocytes will become hyperactive resulting in increased synthesis of β2-microglobulin, which will be released into the blood, and the protein in the blood will naturally be elevated.