Fasting Glucose
Also known as: Blood sugar, Fasting blood glucose, FBG
Fasting glucose measures the amount of sugar in your blood after you have not eaten for several hours, usually overnight. It is a snapshot of your blood sugar at one moment in time.
Why it's measured
It is a common part of routine bloodwork and helps give a picture of how your body manages blood sugar. Because food raises blood sugar, the test is done fasting so results are comparable.
Typical range
Many labs flag fasting glucose roughly between 70 and 99 mg/dL as within the typical range, with higher values labeled borderline or elevated. Whether you truly fasted, and for how long, affects the result.
What high values can mean
A higher fasting glucose is one marker doctors look at when considering how the body handles sugar. A single reading is not a diagnosis; your doctor may consider repeat testing or an A1c for a longer-term view.
What low values can mean
Lower fasting glucose can occur for several reasons. If flagged as low, it’s worth asking your doctor whether it reflects how you prepared for the test or something to look into.
Questions to ask your doctor
- Did I fast long enough for this result to be meaningful?
- Would an A1c add useful context to this single reading?
- Should this be repeated, and if so, when?
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Try the explainerEducational information only — not medical advice, diagnosis, or treatment. Reference ranges vary by lab; always use your own lab's range and discuss results with a qualified clinician.