Fasting sugar Fasting Plasma Glucose (FBG)
The sugar in your blood after a night with no food.
Also printed asFasting Blood Glucose · FBG · Fasting Glucose · Fasting Blood Sugar · FBS · Blood Sugar Fasting · Glucose Fasting · Plasma Glucose Fasting
What it measures
The sugar in your blood after a night without food.
Sets how hard your pancreas has to work each day, and over years it drives nerve, eye, kidney and artery damage.
Why it matters for how long you stay well
Sugar that sits high year after year stiffens arteries and wears out nerves, eyes and kidneys, so keeping this number steady is one of the strongest levers on how long you stay well.
How it shows up in daily life
When it runs high you may feel thirsty, tired an hour after meals, and find yourself getting up at night to pass urine.
High and low readings
When it reads high
Your body is finding it harder to clear sugar after meals.
When it reads low
Your sugar dipped low; usually a long gap between meals.
What moves it
Daily life
- how much refined carbohydrate is on your plate
- walking after meals
- weight around your middle
- short or broken sleep
- how much muscle you carry
Medicines known to shift it
- metformin (lowers it)
- GLP-1 medicines (lower it)
- steroids (raise it)
- diuretics (can raise it)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Insulin resistance scoreKnown mechanism
As this rises, Insulin resistance score is calculated from it
Your insulin resistance score was never measured on your blood. It is your fasting sugar and fasting insulin put through a formula, and this is one half of it.
- Three-month sugar averageKnown mechanism
As this rises, Three-month sugar average moves with it
One is a snapshot of this morning, the other is the album of the last three months. They are built from the same sugar, so they travel together over time.
Common questions
What does Fasting Plasma Glucose measure?
The sugar in your blood after a night without food. Sets how hard your pancreas has to work each day, and over years it drives nerve, eye, kidney and artery damage.
What does a high Fasting sugar result usually mean?
Your body is finding it harder to clear sugar after meals.
What does a low Fasting sugar result usually mean?
Your sugar dipped low; usually a long gap between meals.
What is the usual reference range for Fasting sugar?
A broad adult reference band is 70–100 mg/dL. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Adults
- 70–100 mg/dL
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in mg/dL, mmol/L
Ageing relevance
5/5
A direct input to a validated biological-age algorithm.
One of the nine blood inputs to the PhenoAge biological-age clock (Levine et al., Aging, 2018).
Indian reference data
Published data on this marker in Indian adults: ICMR-INDIAB Phase I (Anjana 2017, n=57,117).
Worth knowing
Your whole bloodstream carries only about a teaspoon of sugar at any moment.
Have a report with this marker on it? Read it in context.
Upload it to Oraia, our health-intelligence tool, for a plain-language read of your markers that a Genoryx doctor can review.
Your biological age is a number you can measure.
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