Because different foods generate different blood sugar (glucose) responses, the timing of your blood sugar is an important factor to consider.
This question has come up a number of times. Commenters have asked whether the one-hour postprandial glucose is timed with the start of the meal or the conclusion of the meal.
In my view, if we simply ignored all aspects of meal composition, then blood glucose should be obtained one hour after the conclusion of a meal. This is because most mixed meals (i.e., mixed in composition among proteins, fats, and carbohydrates) yield peak blood glucose levels at 60-90 minutes after consumption. Timing blood glucose to 60 minutes after the conclusion of a meal puts the sample right about at the peak.
But this is an oversimplification. For instance, here is the blood glucose behavior after so-called "complex" carbohydrates wheat bread, rye bread, rye made with beta glucan, and whole wheat pasta (50 grams carbohydrates each) in slender, healthy volunteers, mean age 29 years:
Note that blood glucose peaks at 35 minutes postprandial. (To convert glucose in mmol/L to mg/dl, multiple by 18. Thus, whole wheat bread increased blood glucose from 94 mg/dl to 122 mg/dl. Also note the lower peak glucose for pasta, but sustained higher glucose levels hours later.)
In another study, older (mean age 64 years), overweight (BMI 27.9) females with diabetes were given 50 grams carbohydrate, 50 grams carbohydrate with olive oil, or 50 grams carbohydrate with butter:
From Thomsen et al 2003. C ontrol meal of soup plus 50 g carbohydrates ( 
), the control meal plus 80 g olive oil ( 
), and the control meal plus 100 g butter (•).
In this experience, note that postprandial glucose peaks 60-120 minutes after the meals (consumed within 10 minutes), delayed more when either oil is included. Blood glucose started at 144 mg/dl and peaked as high as 230 mg/dl with carbohydrates only; peaks were reduced (along with AUC) when oil was included. (Note the differential effect, olive oil vs. butter.)
These two sets of observations give you a range of blood glucose behavior. One side lesson: Carbohydrates should never consumed by themselves, else you will pay with a high blood sugar (not to mention the hypoglycemic response later for many).