For my case I measure improvements by two major indications:
I-Blood test: I do complete CBC test to see differences in blood counts including WBC, lymphocytes and monocytes.
II- Physical observations: This includes spit test, overall skin looking, systematic or local indications such as dandruff, white toung, mouth sores, lymph nodes (swelled, painful?), stool composition (by vision), allerges including sensitivities to chemicals or smokes, etc.