Glucose (Fasting) blood test

The sugar level in your blood after not eating for 8 hours or more.

Typical range (adult men): 70–100 mg/dL
Panel: Other
Also called: Fasting blood sugar, FBG

Reference ranges vary between labs; use the range on your own report. Results need to be read by a doctor alongside your symptoms and other tests.

Why it’s tested

Screens for diabetes and insulin resistance; growth hormone and related compounds can raise it.

What can raise it

Not fasting before the test
Insulin resistance or diabetes
Growth hormone or GH-releasing compounds
Stress and poor sleep

What can lower it

Long fasts or very hard exercise
Too much insulin or some diabetes medication

Getting an accurate result

Test in the morning, especially for hormones, which run highest early in the day.
Fast for 8 to 12 hours beforehand (water is fine).
Stay hydrated, and test at the same lab and time of day each time so results compare fairly.

Compounds that affect Glucose (Fasting)

Monitored with these, based on their known properties:

Other other tests

Questions

What is a normal Glucose (Fasting) level?

A typical adult male reference range is 70–100 mg/dL. Ranges differ for women, by age and between labs, so compare with the range printed on your report.

What does high Glucose (Fasting) mean?

Common reasons include not fasting before the test, insulin resistance or diabetes, growth hormone or GH-releasing compounds and stress and poor sleep. One result outside the range isn't a diagnosis: a doctor will look at it with your other markers and history.

What does low Glucose (Fasting) mean?

Common reasons include long fasts or very hard exercise and too much insulin or some diabetes medication.