Fasting Glucose
Fasting glucose measures blood sugar after at least eight hours without caloric intake and reflects baseline glucose regulation by insulin, liver output, and peripheral uptake. Values of 100 to 125 mg/dL define prediabetes and 126 or higher on repeat testing define diabetes. Trends over time can reveal early metabolic dysfunction before HbA1c changes.
Units: mg/dL; some labs report mmol/L (mmol/L = mg/dL ÷ 18). Check the units on your report before comparing to any range here.
Optimal range: who says what
Institutions, researchers and practitioners draw the line in different places. Each position is listed with who holds it and, where a document states it, a link. How we verify ranges.
- Institution or study70-99 mg/dL normalADA Standards of Care
- Institution or study≤85 mg/dL22-year follow-up of 1,973 healthy men aged 40-59 (Bjørnholt et al. 1999, Diabetes Care)Over 22 years, men in the top quartile of fasting glucose (above 85 mg/dL) had higher cardiovascular mortality than the other three quartiles
- Named practitioner<80 mg/dL, Never above 110-120 mg/dL post-mealDr. Mark Hyman · Blood Tests to Ask Your Doctor ForDisclosure: Hyman co-founded Function Health, which appears in our blood-test comparisons.
- Named practitioner89 mg/dL or lessChris Kresser · When Your 'Normal' Blood Sugar Isn't Normal (Part 2)
- Named practitioner80-86 mg/dLLife Extension · Lab Testing Protocol (Suggested Optimal Ranges)Disclosure: Life Extension sells lab panels that appear in our blood-test comparisons.
- Named practitioner75-85 mg/dLTracey O'Shea (Kresser Institute) · Rethinking Normal Glucose: Why Functional Ranges Improve Early Detection and Outcomes
- Lab reference intervalNormal: 70-99 mg/dL, Prediabetes: 100-125 mg/dL, Diabetes: ≥126 mg/dLWhat a lab report flags against. A lab interval is not an optimal target.
Practitioner targets are individual positions, often tighter than guideline ranges. Each was checked against its article before publishing.
20 of 21 itemized panels
Metabolic Health / Glucose
What is Fasting Glucose?
Fasting glucose measures the amount of sugar (glucose) in your blood after not eating for at least 8 hours. Glucose is your body's primary energy source, derived from carbohydrates you eat. Your pancreas releases insulin to help cells absorb glucose, and fasting glucose shows how well this system works at baseline.
When you fast, your liver releases stored glucose (glycogen) to maintain blood sugar. In healthy individuals, insulin keeps this process balanced. Elevated fasting glucose indicates your body is either not producing enough insulin (Type 1 diabetes), not responding well to insulin (insulin resistance/Type 2), or your liver is releasing too much glucose.
Fasting glucose is the most basic diabetes screening test but has limitations. It only shows a snapshot in time and can be affected by stress, illness, or recent intense exercise. HbA1c and fasting insulin provide complementary information about long-term glucose control and insulin sensitivity.
Beyond Diabetes: Metabolic Health Window
- Pre-diabetes detection: Levels 100-125 mg/dL indicate impaired fasting glucose and increased diabetes risk
- Cardiovascular connection: Even "high-normal" glucose (>90 mg/dL) associated with increased heart disease risk
- Cancer risk: Chronically elevated glucose feeds cancer cell growth through the Warburg effect
- Cognitive impact: High glucose damages brain blood vessels and accelerates cognitive decline
- Longevity marker: Centenarians typically maintain low fasting glucose throughout life
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: Diabetes mellitus, fasting glucose, and risk of cause-specific death (Rao Kondapally Seshasai et al., 2011); Diabetes mellitus, fasting blood glucose concentration, and risk of vascular disease: a collaborative meta-analysis of 102 prospective studies (Sarwar et al., 2010). No single paper sets these cutoffs; for attributed targets see who says what.
Optimal (Longevity)70-85 mg/dL▼
- Associated with lowest all-cause mortality and best metabolic health
- Many longevity-focused practitioners target this range
- Indicates excellent insulin sensitivity and metabolic flexibility
Normal (Standard)85-99 mg/dL▼
- Within standard reference range but may indicate early insulin resistance
- Consider lifestyle optimization and checking fasting insulin to assess HOMA-IR
Pre-diabetes100-125 mg/dL▼
- Impaired fasting glucose
- 5-10% annual conversion to diabetes without intervention
- Aggressive lifestyle modification can reverse
- Consider metformin if lifestyle changes insufficient
Diabetes≥126 mg/dL▼
- Diagnostic for diabetes if confirmed on repeat testing
- Requires medical management
- Check HbA1c for confirmation and long-term control assessment
What raises or lowers Fasting Glucose
Causes of high Fasting Glucose
- Insulin resistance
- Type 2 diabetes
- Physical inactivity
- Obesity
- Chronic stress
- Poor diet
- Medications (steroids, beta blockers)
- Cushing's syndrome
- PCOS
Causes of low Fasting Glucose
- Diabetes medications (insulin, sulfonylureas)
- Excessive fasting
- Intense exercise without eating
- Alcohol on empty stomach
- Insulinoma (rare)
- Reactive hypoglycemia
Symptoms when Fasting Glucose is high or low
When high
- Increased thirst
- Frequent urination
- Fatigue
- Blurred vision
- Slow wound healing
- Numbness/tingling in extremities
Chronic hyperglycemia often asymptomatic until complications develop. Many people discover elevated glucose on routine testing.
When low
- Shakiness
- Sweating
- Rapid heartbeat
- Confusion
- Irritability
- Hunger
- Dizziness
- Headache
Hypoglycemia (<70 mg/dL) is usually symptomatic and requires immediate glucose intake. Common in diabetics on medication.
How to move Fasting Glucose
Effect sizes (how much something moves the marker) appear only where the paper cited under the item states them. Talk to your clinician before starting or changing any medication or supplement.
Reduce Refined Carbohydrates
Cut added sugars and processed carbs. Focus on whole foods with low glycemic index. Cutting refined carbohydrate lowers fasting glucose in people with insulin resistance. Fiber slows glucose absorption.
Time-Restricted Eating
Eating within 8-10 hour window improves glucose regulation. Allow 12+ hours overnight fast. Avoid eating within 3 hours of sleep. Early time-restricted eating (finish eating by 6 PM) most effective.
Build Muscle Mass
Skeletal muscle is largest glucose disposal organ. Resistance training 2-3x/week improves insulin sensitivity. Each kg of muscle added increases glucose uptake capacity significantly.
Morning Movement
Exercise before first meal helps deplete liver glycogen and sensitize muscles to glucose uptake. Even 10-20 minutes of movement improves all-day glucose control.
Optimize Sleep
Poor sleep directly impairs glucose tolerance within days. The National Sleep Foundation recommends 7-9 hours for adults. Short sleep worsens insulin sensitivity and can raise fasting glucose.
When to retest
- Retest in 3 months after lifestyle changes to assess progress
- If borderline, confirm with second fasting test or HbA1c
- Check fasting insulin to calculate HOMA-IR for insulin resistance assessment
- Morning cortisol if glucose elevated despite good diet/exercise
Scientific Evidence
Glucose and Mortality
In 820,900 people from 97 prospective studies, fasting glucose above 100 mg/dL was associated with death, while levels of 70 to 100 mg/dL were not. Diabetes carried an all-cause mortality hazard ratio of 1.80, and a 50-year-old with diabetes died about 6 years earlier on average.
Source: Diabetes mellitus, fasting glucose, and risk of cause-specific death.
Pre-diabetes Progression
In 3,234 adults with elevated fasting and post-load glucose, a lifestyle program aiming for 7% weight loss and 150 minutes of activity a week cut diabetes incidence by 58% versus placebo over 2.8 years; metformin cut it by 31%.
Source: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin.
Dawn Phenomenon
The dawn phenomenon is an early-morning rise in blood glucose, or in insulin need, without preceding low glucose. Defined as a rise of more than 10 mg/dL from the overnight low, it occurs in about 54% of people with type 1 and 55% with type 2 diabetes. Growth hormone-driven insulin resistance is the most likely cause.
Source: The dawn phenomenon revisited: implications for diabetes therapy.
Which Providers Test Fasting Glucose?
Cheapest: Oura Health Panels at $99/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
20 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $99 | 50 | $1.98 | |
| $190 | 100+ | $1.90 | |
| $250 | 65 | $3.85 | |
| $297 | 100+ | $2.97 | |
 Labcorp OnDemand | $338 | 50+ | $6.76 |
 Superpower | $349 | 100+ | $3.49 |
| $349 | 75+ | $4.65 | |
 WHOOP Advanced Labs | $349 | 65 | $5.37 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $375 | 108 | $3.47 | |
| $449 | 83 | $5.41 | |
| $495 | 80+ | $6.19 | |
| $499 | 100+ | $4.99 | |
| $700 | 138 | $5.07 | |
| $829 | 54 | $15.35 | |
| $895 | 100+ | $8.95 | |
| $1188 | 70+ | $16.97 | |
| $1198 | 40+ | $29.95 | |
| $1950 | 130+ | $15.00 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
1 itemized panel does not include Fasting Glucose
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Fasting Glucose. Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Fasting Glucose
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
- Dr. Casey Means: Transform Your Health by Improving Metabolism & Blood Sugar RegulationDisclosure: Huberman Lab has been sponsored by Function Health, which appears in our blood-test comparisons.
- Check These Biomarkers on Your Next Blood Test
- A Deep Dive Into How To Interpret The Results Of Your Blood Testing
- Which Lab Tests are Essential?
- Episode 171: July 2022 Bloodwork Review
- Episode 385: Carnivore Diet and Dr. Baker's Blood Work
Frequently Asked Questions
What is the optimal range for Fasting Glucose?
Published positions differ: 70-99 mg/dL normal (ADA Standards of Care); ≤85 mg/dL (22-year follow-up of 1,973 healthy men aged 40-59 (Bjørnholt et al. 1999, Diabetes Care)). Named practitioners target: <80 mg/dL, Never above 110-120 mg/dL post-meal (Dr. Mark Hyman); 89 mg/dL or less (Chris Kresser); 80-86 mg/dL (Life Extension); 75-85 mg/dL (Tracey O'Shea (Kresser Institute)). Lab reference interval: Normal: 70-99 mg/dL, Prediabetes: 100-125 mg/dL, Diabetes: ≥126 mg/dL. That is what a lab report flags against, not an optimal target.
Which blood test providers include Fasting Glucose?
20 of the 21 blood testing panels we itemize marker by marker include Fasting Glucose in their panels. This biomarker is widely available across major providers.
Related: YouBoost rates lifestyle and supplement interventions by evidence; HRV Zone tracks recovery trends.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed Sep 23, 2026 · First published Sep 30, 2025