You will have regular tests, including blood tests. These blood tests are done to detect and monitor the levels of paraprotein. After treatment your paraprotein levels will hopefully be relatively low.
However, if your myeloma becomes active again, your paraprotein levels will begin to rise. If your paraprotein rises over the course of three subsequent blood tests, this may be an indication that your myeloma may be relapsing.
You may also experience an increase in the symptoms and complications related to myeloma and an obvious deterioration in your general health e.g. increasing pain due to myeloma bone disease and decreasing energy levels due to anaemia.