The answer depends on the medications you are taking, your current level of control and what information you are looking for. For example, people with type 1 diabetes who take insulin four times a day need to check at least as many times. People with type 2 who control their glucose levels with lifestyle or lifestyle and metformin may check only once, or perhaps twice, a day.
In general, people who take insulin at meals will need to check before each meal in order to appropriately dose their insulin, and at bedtime, while people who are controlled with oral medications or basal insulin will usually get all the information they need by checking twice per day at different times of the day.
Most people will end up checking their blood glucose at least sometimes in the morning before they eat; this is known as fasting blood glucose. Fasting checks tell you how your control has been over the night; it can give you an indication if you have eaten the proper amount of carbohydrate at dinner and evening snack and tell you and your health care provider if your evening medications are working appropriately.
Pre-meal checks indicate how your control is in a “fasting state”. Post-meal checks will let you know how your body responds to a specific carbohydrate and fat load. Post-meal checks are helpful for modifying your mealplan, if necessary.
Do you have a (non-medical) question you would like answered? Ask Joslin in the comments! Your question could be answered in a future blog, or in an upcoming video series.