Glucose is a specific form of sugar, one of the simplest. It is the form
found in the bloodstream. "Blood sugar" always refers to blood glucose, and
is abbreviated bG. All bG meters are specific for glucose and will not
respond to other sugars, such as fructose, sucrose, maltose and lactose.

Although sucrose (table sugar) is the most common sugar in food, glucose is
also common. Most fruits, fruit juices, and soft drinks contain large amounts
of glucose, and many foods contain small amounts. This means that you must be
very careful to clean any food residue from your fingers before drawing blood
for a bG check. Since the normal level of bG is only 1g/L (=100mg/dl), it
only takes a tiny speck of glucose on your finger to contaminate the sample
and give you a falsely high reading. 10 *micrograms* of glucose could raise
the reading enough to cause you to overreact dangerously.