"When to test the PPBS; after 90, 110 or 120 minutes of a meal" is a question asked by numerous diabetic patients in HealthUnlocked as well as outside. Patients & many labs follow timing of their choice AND EXPECT A VALUE BELOW 140 mg/dl IN ALL CASES.
I feel, the timing depends on the purpose & state of mind of patient &/or doctor &/or lab.
Purposes can be:
1. If it is to cover up the diet/medication violations & to console oneself or convince the doctor that the patient is following the instructions meticulously and results are fine, test PPBS as late as possible - say after 150 minutes (two & a half hours) or so of completion of food intake.
2. If it is to find out how the Pancreas is working & what is the nearly steady state value, test PPBS at exactly 120 minutes (two hours) of completion of food intake.
3. If it is to find out the peak value of blood sugar following a meal, test PPBS before 90 minutes (one & a half hours) of completion of food intake. Higher the Glycaemic Index (GI) of the food, earlier/faster occurs the peak. In the case of Glucose intake in OGTT, peak occur-res between 30 & 60 minutes (almost at 45 minutes).
Even though blood sugar escalation with food intake and Glucose intake for OGTT are different, following it in the latter case gives a repeatable, comparable & standardised pattern. Please imagine the lines joining test values of the SAME OGTT of the author. Test after 120 minutes will miss LOTS OF HIGHER VALUES. Test at 120 minutes will miss lesser number of HIGH values. Test before 120 minutes will miss only still lesser number of HIGHER values.
Wikipedia on Postprandial_glucose_test ( en.wikipedia.org/wiki/Postp... ) says: "For a 2-hour postprandial test, a meal is eaten exactly 2 hours before the blood sample is taken." It is EATEN and NOT began eating.
In a home OGTT (Glucometer) after consuming 75 gm of Glucose (on completion of three years of normal rice based diet thrice daily & occasionally sweets & coffee/tea with sugar), following are the blood sugar values & timings:
Time | BS
----- | ------
00.0 | 096
30.0 | 199
45.0 | 217
60.0 | 210
90.0 | 195
120.0 | 125
Pictorial/graphical representation of these results are given on top for better appreciation. In this case time gap between first bite & completion of food intake is less than a minute & obviously GI is the highest.
This exercise is done because such a sequence of Blood Sugar test is not seen by me anywhere else. Valuable comments of all readers/members are earnestly solicited.