While it varies, the ideal range for blood glucose in most adults is between 70 and 130 milligrams per deciliter before meals. This increases to less than 180 milligrams per deciliter within two hours of eating, as Healthline explains.
Blood glucose transports needed energy to cells, explains WebMD. Blood glucose levels are tested by either a fasting plasma test or an oral glucose test. Both tests require fasting for at least eight hours. For the fasting test, blood is drawn and tested immediately, while the oral glucose test is taken by consuming a sugary beverage, waiting two hours, then testing glucose levels.