Insulin
Insulin is the pancreatic hormone that drives glucose, amino acid, and fat uptake into cells and suppresses liver glucose output. Elevated fasting insulin signals insulin resistance years before fasting glucose or HbA1c rise and often accompanies obesity, fatty liver, and metabolic syndrome. Low levels may indicate beta cell failure or type 1 diabetes.
Units: µIU/mL; some labs report pmol/L (pmol/L ≈ µIU/mL × 6). 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 studyAbout 5 μIU/mL (lowest quartile)Johnson et al. 2010 (Endocr Pract), 965 patients tested for prediabetesAgainst the lowest quartile (mean 4.9 μIU/mL), the second quartile (mean 8.0) had about twice the odds of prediabetes and the top quartile five times. The patients were mostly white, obese women
- Named practitioner2-5 μIU/mLDr. Mark Hyman · Blood Tests to Ask Your Doctor ForHyman writes mIU/dL; the conventional unit is μIU/mL (= mIU/L). A second Hyman article gives <10 with 2-5 as optimal.Disclosure: Hyman co-founded Function Health, which appears in our blood-test comparisons.
- Named practitioner<5 μIU/mLLife Extension · Lab Testing Protocol (Suggested Optimal Ranges)Disclosure: Life Extension sells lab panels that appear in our blood-test comparisons.
- Named practitioner3-7 μIU/mLTracey O'Shea (Kresser Institute) · Fasting Insulin: The Earliest Marker of Metabolic Dysfunction Most Practitioners Never Order
- Lab reference intervalFasting: 2.6-24.9 μIU/mLWhat 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.
18 of 21 itemized panels
Metabolic Health / Glucose
What is Insulin?
Insulin is a peptide hormone produced by beta cells in the pancreas in response to rising blood glucose (after meals). Insulin's primary job is to shuttle glucose from the bloodstream into cells (muscle, fat, liver) for energy or storage. It also promotes fat storage, suppresses lipolysis (fat breakdown), and inhibits gluconeogenesis (liver glucose production). Measuring fasting insulin provides critical insight into insulin resistance—the condition where cells become less responsive to insulin, forcing the pancreas to produce more insulin to maintain normal blood glucose.
Insulin can rise before glucose does. As insulin resistance develops, the pancreas secretes more insulin to keep glucose normal. In the Whitehall II cohort, insulin sensitivity fell steeply over the five years before diabetes was diagnosed, while fasting glucose rose sharply only in the last three (Tabak 2009). A fasting insulin test can show this compensation while glucose and HbA1c still look normal.
HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) is the gold standard calculated marker: (Fasting Glucose × Fasting Insulin) / 405. HOMA-IR >2.0 indicates insulin resistance; >2.5 is concerning; >5.0 is severe. HOMA-IR is more sensitive than glucose or HbA1c for detecting early metabolic dysfunction and predicts future diabetes, cardiovascular disease, and all-cause mortality.
Why Insulin (and Insulin Resistance) Matters for Longevity
- Metabolic health: Insulin resistance is THE root cause of metabolic syndrome—obesity (especially visceral fat), hypertension, dyslipidemia (high triglycerides, low HDL), fatty liver, type 2 diabetes.
- Cardiovascular disease: Insulin resistance drives atherosclerosis, hypertension, and inflammation. High insulin (hyperinsulinemia) independently predicts heart attacks, stroke, and CVD mortality, even with normal glucose.
- Alzheimer's disease (Type 3 Diabetes): Insulin resistance in the brain impairs glucose metabolism and promotes amyloid plaque accumulation. Alzheimer's is now called "Type 3 Diabetes." High insulin associated with 2-3x higher dementia risk.
- Cancer: Insulin is a growth factor. Chronic hyperinsulinemia promotes cell proliferation and cancer growth (breast, colon, prostate). Insulin resistance associated with 30-50% higher cancer risk.
- Aging and longevity: Lower insulin and insulin sensitivity are hallmarks of longevity. Centenarians have exceptional insulin sensitivity. Calorie restriction and fasting extend lifespan partly by lowering insulin.
- PCOS: Insulin resistance drives androgen excess in women, causing PCOS (irregular periods, hirsutism, infertility). Lowering insulin reverses PCOS.
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: Fasting insulin, insulin resistance, and risk of cardiovascular or all-cause mortality in non-diabetic adults: a meta-analysis (Zhang et al., 2017); Fasting insulin concentrations and incidence of hypertension, stroke, and coronary heart disease: a meta-analysis of prospective cohort studies (Xun et al., 2013); Plasma insulin and cardiovascular mortality in non-diabetic European men and women: a meta-analysis of data from eleven prospective studies (DECODE Insulin Study Group, 2004). No single paper sets these cutoffs; for attributed targets see who says what.
Optimal (Longevity)<5 mcIU/mL (fasting)▼
- Exceptional insulin sensitivity
- Associated with longevity, low CVD risk, optimal metabolic health
- Target for healthspan optimization
Good (Standard)5-7 mcIU/mL▼
- Normal insulin sensitivity
- Acceptable for most people but room for improvement with lifestyle optimization
Suboptimal (Early Insulin Resistance)7-10 mcIU/mL▼
- Mild insulin resistance
- Beta cells compensating to maintain normal glucose
- Intervene NOW with diet, exercise, weight loss to reverse
Insulin Resistance10-15 mcIU/mL▼
- Moderate insulin resistance
- HOMA-IR likely >2.5
- High risk of progressing to prediabetes/diabetes
- Requires aggressive lifestyle intervention
- Fasting insulin, insulin resistance, and risk of cardiovascular or all-cause mortality in non-diabetic adults: a meta-analysis.
- Fasting insulin concentrations and incidence of hypertension, stroke, and coronary heart disease: a meta-analysis of prospective cohort studies.
- Plasma insulin and cardiovascular mortality in non-diabetic European men and women: a meta-analysis of data from eleven prospective studies.
What raises or lowers Insulin
Causes of high Insulin
- Obesity: Visceral fat secretes inflammatory cytokines (TNF-alpha, IL-6) and free fatty acids that block insulin signaling.
- Sedentary lifestyle: Physical inactivity reduces GLUT4 expression in muscle, worsening insulin resistance.
- High-carb, processed diet: Chronic carb/sugar intake causes chronic hyperinsulinemia → downregulation of insulin receptors → resistance.
- Metabolic syndrome: Cluster of visceral obesity, hypertension, dyslipidemia, insulin resistance. Affects 35% of US adults.
- Genetics: Family history of type 2 diabetes increases risk. Certain ethnicities (South Asian, Hispanic, African American) have higher risk.
- PCOS: Insulin resistance drives ovarian androgen production in 70-80% of PCOS cases.
- Chronic stress and cortisol excess: Cortisol promotes gluconeogenesis and antagonizes insulin.
- Sleep deprivation: Even short-term sleep restriction worsens insulin sensitivity.
- Medications: Glucocorticoids (prednisone), atypical antipsychotics (olanzapine), protease inhibitors (HIV meds).
- Aging: Insulin sensitivity declines with age due to sarcopenia, fat gain, and mitochondrial dysfunction.
Causes of low Insulin
- Type 1 diabetes: Autoimmune destruction of pancreatic beta cells → no insulin production → high glucose, low/absent insulin.
- Advanced type 2 diabetes with beta cell exhaustion: After years of compensatory hyperinsulinemia, beta cells fail → insulin production drops → glucose rises.
- Insulinoma (very rare): Insulin-secreting pancreatic tumor causes episodic hypoglycemia with inappropriately high insulin. Diagnosed with supervised fasting test.
- Exogenous insulin use: Type 1 diabetics or advanced type 2 diabetics on insulin therapy will have high measured insulin.
Symptoms when Insulin is high or low
When high
Symptoms of hyperinsulinemia and insulin resistance:
- Weight gain, difficulty losing weight (especially belly fat)
- Constant hunger, cravings for carbs/sugar
- Fatigue, energy crashes after meals (reactive hypoglycemia)
- Brain fog, poor concentration after meals
- Acanthosis nigricans (dark, velvety skin patches on neck, armpits, groin)
- High triglycerides (>150 mg/dL), low HDL (<40 men, <50 women)
- High blood pressure (>130/85)
- Fatty liver (elevated ALT, AST)
- PCOS in women (irregular periods, hirsutism, infertility)
- Skin tags (small benign growths, marker of insulin resistance)
High fasting insulin >10 mcIU/mL indicates insulin resistance even if glucose is normal. HOMA-IR >2.0 confirms insulin resistance.
When low
Low insulin is rare and usually indicates:
- Type 1 diabetes: Autoimmune destruction of pancreatic beta cells. No insulin production. Requires exogenous insulin replacement.
- Advanced type 2 diabetes with beta cell failure: After years of hyperinsulinemia, beta cells burn out and insulin production drops. Glucose rises dramatically.
- Hypopituitarism: Pituitary failure reduces growth hormone and other hormones that stimulate insulin secretion.
Low insulin with high glucose = beta cell failure (type 1 or advanced type 2 diabetes). Requires insulin therapy.
How to move Insulin
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.
Reverse Insulin Resistance with Diet (Most Effective)
- Low-carb or ketogenic diet: Restrict carbs to <100 g/day (low-carb) or <50 g/day (keto). Eliminates insulin spikes, depletes liver glycogen, forces fat oxidation. Fasting insulin often falls within weeks.
- Intermittent fasting (IF): 16:8 (fast 16 hours, eat within 8-hour window) or alternate-day fasting. Fasting drops insulin to baseline, enhances insulin sensitivity, promotes autophagy.
- Eliminate processed carbs and sugar: White bread, pasta, rice, sugary drinks, desserts spike insulin. Replace with whole foods, vegetables, protein, healthy fats.
- Prioritize protein and fiber: Protein (1.6-2.2 g/kg) preserves muscle during weight loss. Fiber (25-35 g/day) slows glucose absorption, reducing insulin spikes.
Exercise (Resistance + HIIT)
- Resistance training: THE most effective exercise for improving insulin sensitivity. Heavy compound lifts (squats, deadlifts, bench) 3-4x/week build muscle, which is metabolically active and glucose-hungry. Increases GLUT4 receptors (glucose transporters) in muscle.
- High-intensity interval training (HIIT): 20-30 min sessions 2-3x/week improve insulin sensitivity more than steady-state cardio. Depletes muscle glycogen, forcing insulin-independent glucose uptake.
- Post-meal walks: 10-15 min walk after meals blunts the post-meal rise in glucose and insulin. Simple and effective.
Weight Loss (Especially Visceral Fat)
- Lose 5-10% body weight: Even modest weight loss dramatically improves insulin sensitivity. Fasting insulin falls as weight comes off.
- Target visceral fat: Visceral (belly) fat is metabolically toxic, secreting inflammatory cytokines and free fatty acids that worsen insulin resistance. Measure waist circumference and track it as you lose fat.
- Calorie deficit + resistance training: Preserve muscle mass while losing fat. Muscle is insulin-sensitive; fat (especially visceral) is insulin-resistant.
Metformin (if lifestyle insufficient)
- Metformin: 500-1000 mg twice daily. First-line medication for insulin resistance and prediabetes. Reduces hepatic glucose production, improves insulin sensitivity, aids weight loss.
- Evidence: In the Diabetes Prevention Program, metformin cut diabetes incidence by 31% versus placebo in people at high risk, and the lifestyle program by 58% (Knowler 2002).
- Side effects: GI upset (diarrhea, nausea) is common and usually resolves. Start low (500 mg once daily), titrate up. May lower B12—supplement or check annually.
Source: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin.
Sleep and Stress Management
- Sleep 7-9 hours: Short sleep worsens insulin sensitivity. Chronic sleep debt (≤6 hours) doubles diabetes risk.
- Manage stress: Chronic stress elevates cortisol, which promotes gluconeogenesis and insulin resistance. Meditation, deep breathing, yoga improve insulin sensitivity.
- Avoid late-night eating: Eating close to bedtime worsens insulin resistance due to circadian misalignment. Stop eating 3 hours before bed.
When to retest
- Baseline: Check fasting insulin (with fasting glucose) if risk factors for insulin resistance: overweight/obesity, family history of diabetes, PCOS, metabolic syndrome, fatty liver.
- Calculate HOMA-IR: (Fasting Glucose mg/dL × Fasting Insulin mcIU/mL) / 405. Higher HOMA-IR means more insulin resistance; cutoffs vary by population and lab.
- After lifestyle intervention: Retest fasting insulin and glucose after 3-6 months of diet, exercise, weight loss. Fasting insulin should fall if the changes are working.
- If starting metformin: Retest after 3 months.
- Annual screening: For anyone with prediabetes, metabolic syndrome, PCOS, or strong family history of diabetes.
- Fasting required: Must fast 8-12 hours (water only). Test in morning. No food, coffee, or supplements before test.
Scientific Evidence
Metabolic Changes Before Type 2 Diabetes
In the Whitehall II cohort (6,538 civil servants, 505 new diabetes cases), insulin sensitivity fell steeply over the 5 years before diagnosis, and fasting and post-load glucose rose sharply only in the final 3 years. Beta-cell function rose briefly 3-4 years before diagnosis, then fell.
Fasting Insulin and Ischemic Heart Disease
In 2,103 men aged 45-76 from Quebec City followed for 5 years, fasting insulin was 18% higher in those who developed ischemic heart disease than in matched controls. Each 1 SD higher insulin carried an odds ratio of 1.7, still 1.6 after adjusting for triglycerides, ApoB, LDL, and HDL cholesterol.
Source: Hyperinsulinemia as an independent risk factor for ischemic heart disease.
Insulin Resistance and Alzheimer's Disease
De la Monte and Wands review evidence that disturbed brain insulin and IGF signaling appear early in Alzheimer's disease and could account for many of its lesions, and argue that 'type 3 diabetes' describes the disease. Much of the supporting evidence comes from laboratory and animal models.
Source: Alzheimer's disease is type 3 diabetes-evidence reviewed.
Which Providers Test Insulin?
Cheapest: Oura Health Panels at $99/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
18 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 | |
| $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.
3 itemized panels do not include Insulin
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 Insulin. Check with them directly.
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Experts discussing Insulin
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
- When You Should Worry About LDL Cholesterol
Frequently Asked Questions
What is the optimal range for Insulin?
Published position: About 5 μIU/mL (lowest quartile) (Johnson et al. 2010 (Endocr Pract), 965 patients tested for prediabetes). Named practitioners target: 2-5 μIU/mL (Dr. Mark Hyman); <5 μIU/mL (Life Extension); 3-7 μIU/mL (Tracey O'Shea (Kresser Institute)). Lab reference interval: Fasting: 2.6-24.9 μIU/mL. That is what a lab report flags against, not an optimal target.
Which blood test providers include Insulin?
18 of the 21 blood testing panels we itemize marker by marker include Insulin 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