Fasting plasma glucose

A glucose test is a type of blood test used to determine the amount of glucose in the blood. It is mainly used in screening for prediabetes or diabetes. Patients are instructed not to consume anything but water during the fasting period. Caffeine will also distort the results. If the person eats during the period in which he or she is supposed to have been fasting then they may show blood sugar levels that may cause his or her doctor to think the person has or is at increased risk of having diabetes. In people already having diabetes, blood glucose monitoring is used with frequent intervals in the management of the condition.

There are several different kinds of glucose tests:

A range of 4 to 5.5 mmol/l (70 to 99 mg/dl) before a meal is normal. Continual fasting levels of 5.5 to 7 mmol/l (101–125 mg/dl) causes concern of possible prediabetes and may be worth monitoring. 7 mmol/l (126 mg/dl) and above means a risk of diabetes.

After a 12‑hour fast, a range of 3.9 to under 5.5 mmol/l (70.2 to 100 mg/dl) is normal; a level of 5.6 to under 7 mmol/l (100 to 126 mg/dl) is considered a sign of prediabetes.

A level of < 7.8 mmol/l (140 mg/dl) 90 minutes after a meal is normal.

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