Fasting Blood Glucose
Your morning baseline for metabolic health — and one of the earliest signals of insulin resistance, years before diabetes shows up on a standard panel.
Track This Free → ← All BiomarkersWhat Is Fasting Blood Glucose?
Fasting blood glucose is the concentration of sugar in your blood after at least eight hours without eating, measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L), and it is the single most common screening test for prediabetes and type 2 diabetes.
Because you have not eaten, fasting glucose reflects how well your body manages blood sugar at rest — a job handled mainly by insulin from the pancreas and glucose storage in the liver. When cells stop responding to insulin efficiently (insulin resistance), fasting glucose creeps upward long before a person meets the threshold for diabetes. That slow drift is why a rising fasting number, even inside the 'normal' band, is a meaningful early warning rather than a pass/fail result.
Fasting Blood Glucose Normal Range and Reference Values
| Category | Value | Notes |
|---|---|---|
| Normal (non-diabetic) | 70–99 mg/dL | 3.9–5.5 mmol/L |
| Prediabetes | 100–125 mg/dL | 5.6–6.9 mmol/L |
| Diabetes range | 126 mg/dL or higher | 7.0 mmol/L or higher |
| Low (hypoglycemia) | Below 70 mg/dL | Below 3.9 mmol/L |
What Causes Fasting Blood Glucose to Change
The most common drivers behind a change in Fasting Blood Glucose are:
- Insulin resistance — the earliest and most common driver of a slow upward trend
- Poor sleep the night before — a single bad night measurably raises next-morning glucose
- Chronic stress and elevated cortisol, which prompt the liver to release glucose
- Dawn phenomenon — a natural early-morning hormone surge that lifts glucose in some people
- Refined-carbohydrate or alcohol intake the evening before
- Certain medications including steroids and some diuretics
How Hunuu Tracks Fasting Blood Glucose
Hunuu reads blood glucose from Apple Health (HKQuantityTypeIdentifierBloodGlucose) and Health Connect, automatically picking up Dexcom Clarity, FreeStyle LibreLink, and OneTouch Reveal. A rising fasting baseline, cross-referenced with your HRV and sleep architecture, is one of the metabolic inputs the HIP score watches. Under the canonical HIP rule, glucose is zero-weighted until you have at least three readings in 14 days — missing data never lowers your score, it simply does not yet contribute.
Frequently Asked Questions
What is a normal fasting blood glucose level?
For a non-diabetic adult, a normal fasting glucose is 70 to 99 mg/dL (3.9 to 5.5 mmol/L). Readings of 100 to 125 mg/dL indicate prediabetes, and 126 mg/dL or higher on two separate tests indicates diabetes.
Is a fasting glucose of 100 bad?
A fasting glucose of 100 mg/dL sits at the very bottom of the prediabetes range. It is not an emergency, but it is an early signal worth acting on with sleep, movement, and diet changes, and worth rechecking. A single borderline reading should be confirmed before drawing conclusions.
Why is my morning blood sugar higher than at bedtime?
This is often the dawn phenomenon — a normal early-morning release of cortisol, growth hormone, and other hormones that signals the liver to release glucose in preparation for waking. Poor sleep and late-evening carbohydrates can amplify it.
Does stress raise fasting blood glucose?
Yes. Cortisol and adrenaline released during chronic or acute stress prompt the liver to release stored glucose and can make cells more insulin-resistant, both of which raise fasting readings.
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