Glucose can be checked either intravenously or capillary, and whether it is intravenously or capillary, it should be checked fasting and 2 hours after a meal.
In terms of testing methods, what we usually call blood glucose testing can be done either intravenously or capillary, and intravenous blood glucose needs to be tested in a medical facility, while capillary blood glucose can be tested at home, which is much more convenient but less accurate than intravenous blood glucose.
In terms of time points for testing, you can check your morning fasting blood glucose, pre-meal blood glucose, 2-hour post-meal blood glucose, and bedtime blood glucose, so there are 7 time points for blood glucose testing a day.
Fasting blood glucose testing requires fasting starting after 8 pm the night before, and the fasting time is usually 10-12 hours; 2-hour postprandial blood glucose is the blood glucose 2 hours after eating, counting the time from the first bite of the meal.