What are the differences between fasting blood sugar and fasting plasma sugar?

See below: Whole blood sugar is before the liquid (plasma) is separated from the cells. Plasma glucose values are generally 10-12% higher than whole blood values.

Minor difference: There is about a 15% difference between whole blood glucose and plasma glucose, with the plasma glucose being higher. If you use a fingerstick glucose monitor, it is measuring whole blood glucose, whereas when you have blood drawn and sent to the lab, it is measuring plasma glucose. Some fingerstick meters will correct for the difference by adding 15% automatically.