Normal blood sugar levels should be less than 100 mg/dL when fasting and less than 140 mg/dL two hours after eating, according to WebMD. People without diabetes tend to have blood sugar levels of around 60 to 90 mg/dL before eating.
A fasting blood sugar fasting test measures someone's blood sugar levels with the aim of forming a diabetes diagnosis. If blood sugar levels are more than 126 mg/dL more than eight hours after eating, there's a chance the individual has diabetes. An alternative approach is the oral glucose tolerance test, which measures blood sugar levels before and two hours after a sugary drink. Diabetes may be present if levels are 200 mg/dL two hours after consuming the drink. Low blood sugar levels vary, but many assume low is 60 mg/dL, as noted by WebMD.