Actual time for testing PP Blood sugar.

My wife (55)is achronic diabetic patient(9yrs).Her present FBSis120 &PP214.Urea24 ,Cholesterol152,TG81,Creatinine1.0, HDL48 ,LDL88 VLDL16,UrineAlbumin-Nil.The PP does not reduce in spite of several attempts.Please advise how to reduce PP level.The blood for Pp was taken after 1.5 Hrs of taking food. In the beginning we used to take PPblood consuming 75 gm glucose counted346.Another day it counted 317.As I was shocked another Dr. advised me to go for PP after 1.5 Hrs of stomach full food and it showed 285.Then another Dr. advised me to go for PP at 2 Hrs of taking stomach full food.It counted246,Another Dr. advised me to test PP at 2hrs of taking normal break fast(not stomach full).It showed210.Now after 1.5 hrs.PPis 214.My doubt is how to reduce PP into normal.The PP differs about 40 between 1.5 and 2 hrs.(in 30 minutes). When & How much food /glucose should be taken for blood PP.My wife's BP is 100/70 & pulse is 101. She takes OlmyD20. Dr says it's all right.It helps Kidny