Understanding Optimal vs Reference Ranges in Blood Work
If you’ve ever been told “your labs are normal” but still struggle with fatigue, inflammation, weight gain, brain fog, blood sugar issues, or chronic disease risk, you’re not alone.
One of the most important—and most misunderstood—concepts in medicine is this:
Reference ranges are not the same as optimal or healthy ranges.
Understanding the difference between normal lab values and optimal lab values can be the difference between early prevention and late diagnosis.
What Are Lab Reference Ranges?
Most laboratory reference ranges are based on statistical averages from a local population, not on markers of ideal health.
This means:
- Reference ranges shift as population health declines
- “Normal” often reflects what is common, not what is healthy
- Early metabolic, immune, and inflammatory dysfunction is frequently missed
In the U.S., where insulin resistance, chronic inflammation, nutrient deficiencies, and metabolic disease are widespread, reference ranges increasingly reflect a metabolically unhealthy baseline.
Functional and integrative medicine instead focuses on optimal lab ranges—levels associated with resilience, longevity, immune balance, and disease prevention.
Key Lab Markers Where “Normal” Can Be Misleading
Vitamin D (25-OH Vitamin D)
Vitamin D reference ranges vary widely by region and have declined significantly in recent years, particularly after COVID-related lifestyle changes.
- Optimal: ~60–70 ng/mL for the average adult (research suggests 85-100 optimal in a cancering person)
- Many labs flag >50 ng/mL as “high”
- Reality: Levels around 65 are associated with improved immune function, lower cancer risk, and reduced inflammation
Low reference ranges reflect widespread deficiency—not optimal physiology.
Fasting Insulin
One of the most critical markers of metabolic health—and one of the most underappreciated.
- Some reference ranges: up to 25–30 µIU/mL
- Optimal: ≤4 µIU/mL
A fasting insulin in the teens or 20s reflects severe insulin resistance, not normal metabolism. Elevated insulin is associated with:
- Metabolic syndrome
- Cardiovascular disease
- Neurodegeneration
- Cancer progression
Fasting Glucose
Blood sugar interpretation is skewed because so many people run chronically high glucose.
- Optimal: 55–85 mg/dL
- Many labs flag glucose in the 60s as “low”
This often leads people to believe they are hypoglycemic when they are not. In reality, lower fasting glucose frequently reflects excellent insulin sensitivity.
Hemoglobin A1C
A long-term marker of blood sugar exposure.
- Optimal: ≤5.0%
- “Normal” reference: up to 5.6%
An A1C of 5.6 is borderline prediabetes, not ideal health. Waiting for an abnormal flag delays intervention for years.
C-Reactive Protein (CRP)
A marker of systemic inflammation.
- Lab reference: often <5.0 mg/L
- Optimal: <1.0 mg/L
Anything above 1.0 represents active inflammation, which increases risk for cardiovascular disease, autoimmune conditions, neuroinflammation, and cancer.
Neutrophil-to-Lymphocyte Ratio (NLR)
A powerful immune system marker.
- Optimal: ~1:1 to 2:1
Deviations may reflect:
- Chronic stress
- Infection
- Immune suppression or activation
- Inflammatory or malignant processes
LDH (Lactate Dehydrogenase)
A surrogate marker of mitochondrial and cellular stress.
- Optimal: 145–175 U/L
- Too low: possible magnesium or B6 deficiency
- Too high: mitochondrial stress, hypoxia, inflammation, or tissue breakdown
Ferritin (Iron Storage)
Ferritin is both an iron marker and an inflammatory marker.
- Optimal: 45–100 ng/mL
- Low: anemia, fatigue, hypoxia
- High: inflammation, immune activation, oxidative stress, iron overload
Homocysteine
A marker of methylation, cardiovascular risk, and neuroinflammation.
- Optimal: 6–8 µmol/L
High homocysteine may indicate:
- B12, B6, or folate deficiency
- Poor methylation
- Brain and systemic inflammation
Both high and very low levels suggest dysfunction.
Triglycerides
A key marker of liver and metabolic health.
- Optimal: 70–90 mg/dL
- High levels suggest:
- Fatty liver disease
- An unhealthy or Higher than needed carbohydrate/sugar intake
- Insulin resistance
- Metabolic syndrome
- Liver toxicity
MCV (Mean Corpuscular Volume)
Reflects red blood cell size and nutrient status.
- Optimal: ~90 fL
- High MCV: B12 deficiency, anemia, methylation issues, medication effects (e.g., metformin)
- Low MCV: B6, zinc, magnesium deficiency, gut dysfunction, chronic stress
ESR (Erythrocyte Sedimentation Rate)
A marker of blood viscosity and inflammation.
- Optimal: <10 mm/hr
Elevated ESR suggests:
- Thick, clumpy blood
- Autoimmune activity
- Reduced tissue oxygenation
- Increased angiogenic signaling (e.g., VEGF)
Why Understanding Optimal Lab Values Matters
Relying only on reference ranges means:
- Disease is detected late
- Prevention is missed
- Patients are falsely reassured
Interpreting labs through an optimal, functional lens allows for:
- Earlier intervention
- Improved immune and metabolic resilience
- Reduced inflammation
- Better energy, cognition, and longevity
- Improved cancer outcomes and quality of life
The Bottom Line
Normal is not the same as healthy.
And average is not the goal.
Your lab values tell a story—one that deserves deeper interpretation than a checkbox on a report.
Scientific References
- Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266–281.
- Grant WB et al. Vitamin D supplementation and cancer outcomes. Anticancer Res. 2020.
- Kraft JR. Diabetes epidemic & insulin resistance. Diabetes Metab Res Rev. 2003.
- Shulman GI. Cellular mechanisms of insulin resistance. J Clin Invest. 2000.
- American Diabetes Association. Standards of Medical Care in Diabetes. Diabetes Care.
- Ridker PM. CRP and cardiovascular risk. Circulation. 2003.
- Guthrie GJ et al. The systemic inflammation-based neutrophil–lymphocyte ratio. Cancer Treat Rev. 2013.
- Vander Heiden MG et al. Mitochondrial metabolism and cancer. Science. 2009.
- Kell DB, Pretorius E. Ferritin and inflammation. BMC Med. 2014.
- Clarke R et al. Homocysteine and vascular disease. N Engl J Med. 1991.
