Fasting Glucose
Fasting Blood Sugar
- Sample
- Blood
- Usual units
- mg/dL
- Fasting
- Usually done fasting. Follow the fasting instructions your lab or doctor gives you.
Also known as Fasting Blood Sugar · FBS · Glucose Fasting · Blood Sugar Fasting · Fasting Plasma Glucose · FPG · Glucose - Fasting · Blood Glucose · Blood Glucose Levels · Blood Sugar · Blood Sugar Levels
What this test measures
Glucose is a sugar cells use for energy, and its concentration in blood shifts with meals. A fasting glucose test measures it after a period without food, giving a reading at a controlled, comparable point rather than one affected by a recent meal. It is usually reported in milligrams per deciliter (mg/dL).
Reading your report
There isn’t one standard range for this test — each lab prints its own. Use the range shown next to your result.
Fasting Glucose unit converter
Convert Fasting Glucose units
Labs print this test in mg/dL or mmol/L depending on where the sample was run.
Related guides
- Guide
Why the same blood test has different "normal" ranges at different labs
Reference intervals are built from each lab's own population and equipment, which is why two labs can print different ranges for the same sample.
- Guide
Reference interval, cutoff, and the "optimal" numbers online: three different things
The range beside your result, the target a website quotes, and the threshold that defines a condition are built in different ways and answer different questions.
- Guide
Why the same lab printed a different reference range for you this year
Ranges are not fixed constants. The lab can change method, revise its reference group, or apply a range that depends on your age — none of which is an error.
- Guide
HbA1c and fasting glucose: a three-month average and a single moment
One is a snapshot of the morning you gave blood, the other reflects roughly three months. Why they can disagree, and what the estimated average glucose row is.
- Guide
Why your report says "fasting required", and what changes when it isn't
Which tests ask you to fast, for how long, and what eating beforehand does to the numbers — plus why a report often prints whether you fasted.
- Guide
mg/dL and mmol/L: why the same result is printed two different ways
Two unit systems are in routine use, and a marker's number changes completely between them. How to tell which one you are holding, and why you cannot compare across them by eye.