Why a Fasting Glucose of 84 mg/dL May Be the Key to Preventing Type 2 Diabetes
Introduction
If you've ever looked at your lab results and breathed a sigh of relief because your fasting glucose was under 100 mg/dL, you're not alone. Most traditional reference ranges label any fasting blood sugar below 100 as "normal." But new research suggests that this range may not be optimal. In fact, a landmark study conducted by researchers at Kaiser Permanente shows that the risk for type 2 diabetes increases significantly with fasting glucose levels above 84 mg/dL.
This blog post dives into that pivotal research article, "Normal Fasting Plasma Glucose and Risk of Type 2 Diabetes Diagnosis" published in the American Journal of Medicine, and explores what it means for your health. If you're aiming for optimal—not just average—health, this information is essential.
Understanding Fasting Glucose and Its Importance
Fasting plasma glucose (FPG) is one of the simplest and most common ways to assess blood sugar regulation. It reflects your body’s glucose levels after an 8-12 hour fast, typically measured first thing in the morning.
According to standard lab reference ranges:
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Normal: <100 mg/dL
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Prediabetes: 100–125 mg/dL
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Diabetes: ≥126 mg/dL
But here's the catch: these ranges are based on statistical norms, not on what is physiologically optimal. In other words, they reflect the middle of the bell curve in a generally unhealthy population—not the range associated with the best long-term health outcomes.
The Landmark Kaiser Study: What It Found
In their 2008 paper, researchers Nichols, Hillier, and Brown followed 46,578 adults who had fasting glucose levels considered "normal" (under 100 mg/dL). The study, published in The American Journal of Medicine, aimed to understand how small variations within the normal range could influence future diabetes risk.
Key Findings:
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Compared to individuals with FPG <85 mg/dL, those with higher FPG were at significantly increased risk for type 2 diabetes.
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For every 1 mg/dL increase above 84, the risk of developing type 2 diabetes increased by approximately 6%.
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Individuals with FPG levels of 95-99 mg/dL had a more than 2-fold increase in risk compared to those with levels below 85 mg/dL.
This means that a person with a fasting glucose of 94 mg/dL is not truly “normal” but actually at elevated risk for developing metabolic disease.
Optimal vs. Normal: Why Reference Ranges Mislead
Statistical vs. Functional Health Ranges
Lab reference ranges are typically derived from the middle 95% of a given population. But if that population has high rates of obesity, insulin resistance, and metabolic syndrome (as is common in the U.S.), then the "normal" range may reflect a state of dysfunction rather than health.
Functional Medicine Perspective
Functional medicine practitioners have long advocated for optimal ranges that reflect the healthiest segment of the population. For fasting glucose, this range is usually:
Optimal: 70–84 mg/dL
This aligns perfectly with the Kaiser Permanente study, which shows that keeping fasting glucose below 85 mg/dL is associated with the lowest future risk of type 2 diabetes.
Why Fasting Glucose Creeps Up
Even small increases in fasting glucose can indicate underlying metabolic dysfunction. Here are common reasons for elevated fasting glucose:
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Insulin resistance: Often due to poor diet, inactivity, or excess visceral fat.
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Poor sleep: Increases cortisol, which raises glucose.
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Chronic stress: Elevates fasting glucose via stress hormones.
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Overeating at night: Late-night eating can elevate morning glucose.
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Micronutrient deficiencies: Especially magnesium, chromium, and zinc.
The Role of Fasting Glucose in Metabolic Health
Fasting glucose is a simple marker but offers deep insight into your health:
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Early warning system: Glucose levels in the 85-99 range may signal early metabolic dysfunction.
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Predictor of insulin resistance: Even without elevated fasting insulin, rising glucose often precedes full-blown metabolic syndrome.
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Cardiovascular risk: Elevated fasting glucose is linked to increased risk for heart disease, even in non-diabetics.
Beyond Fasting Glucose: Other Markers to Watch
To get a comprehensive picture of blood sugar regulation, consider the following tests:
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HbA1c: Reflects 3-month average glucose; optimal <5.4%
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Fasting insulin: Ideal is 2-6 uIU/mL
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HOMA-IR: Measures insulin resistance; optimal is <1.0
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Postprandial glucose: Should be <120 mg/dL at 1-2 hours after meals
What You Can Do to Optimize Your Blood Sugar
1. Prioritize Protein and Fiber
These help stabilize blood sugar and improve insulin sensitivity. Aim for 20-30g of protein per meal and high-fiber vegetables.
2. Eliminate Refined Carbs and Sugars
Highly processed carbs spike insulin and raise fasting glucose over time.
3. Embrace Movement
Exercise improves glucose uptake and lowers insulin resistance. Combine:
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Resistance training 2-3x/week
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Walking after meals
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Zone-2 cardio (e.g., brisk walking or cycling)
4. Improve Sleep Quality
Poor sleep drives insulin resistance. Aim for 7-9 hours of high-quality sleep and track with devices like Oura Ring or Apple Watch.
5. Use Targeted Supplements
Some supplements can support healthy glucose metabolism:
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Berberine 5x
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Mag Glycinate
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Alpha-lipoic acid (ALA-SR)
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Inositol (myo- and D-chiro)
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Chromium picolinate
6. Try Intermittent Fasting
Eating within a 6-10 hour window can improve insulin sensitivity and lower fasting glucose.
Final Thoughts: Don’t Settle for "Normal"
The Kaiser Permanente study is a wake-up call for anyone relying on standard lab ranges to define their health. If your fasting glucose is 90 or 95 mg/dL, your doctor may say you're fine. But the data clearly shows you're on a path toward insulin resistance and type 2 diabetes.
Functional and integrative practitioners have long used tighter optimal ranges to assess risk and guide early intervention. Keeping fasting glucose under 85 mg/dL could be one of the most powerful things you can do to prevent chronic disease.
References
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Nichols GA, Hillier TA, Brown JB. Normal Fasting Plasma Glucose and Risk of Type 2 Diabetes Diagnosis. Am J Med. 2008 Jun;121(6):519–524. doi:10.1016/j.amjmed.2008.02.026
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Kraft JR. Diabetes Epidemic & You. Phoenix: Trafford Publishing; 2008.
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Monnier L, Colette C. Glycemic variability: should we and can we prevent it? Diabetes Care. 2008 Feb;31 Suppl 2:S150-4.
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Nuttall FQ. Body weight, not insulin, determines insulin sensitivity in normal humans. Diabetes Care. 2008 Aug;31(8):1493-6.
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American Diabetes Association. Standards of Medical Care in Diabetes. 2024.
Need help optimizing your blood sugar? Our clinic offers advanced lab testing, lifestyle coaching, and evidence-based therapies to help you reverse insulin resistance and reclaim your health. Contact us today to get started.