How to Catch Insulin Resistance Early - High-Yield Tests Part 1

Nick Sterling, MD, PhD

In this episode, we cover the highest-yield lab tests to spot insulin resistance early—often years before routine screening would. I walk through how insulin works, why insulin resistance can be silent for a decade, and which metrics actually move the needle for long-term metabolic health.We dig into fasting glucose and A1C, fasting insulin, and combined indices like HOMA-IR and QUICKI. I also explain when an oral glucose tolerance test or a continuous glucose monitor can add value, the limitations of single time-point labs, and why calibration matters for CGMs. Finally, I preview how lipid test — particularly triglyceride-to-HDL ratio—can flag insulin resistance.Chapter Markers00:00 — Intro00:28 — Insulin resistance as a foundation01:11 — Common causes of mortality in U.S.02:07 — What insulin does (and what goes wrong)02:57 — Glucose tests: fasting glucose & A1C basics04:20 — Early signal: fasting insulin (typical ranges)05:16 — Combined indices: HOMA-IR & QUICKI (cutoffs & caveats)06:18 — OGTT & CGM07:31 — Continuous glucose monitor caveats09:10 — TG/HDL ratio for insulin resistanceHOMA-IR Calculatorhttps://www.mdcalc.com/calc/3120/homa-ir-homeostatic-model-assessment-insulin-resistanceQUICKI Calculatorhttps://www.mdapp.co/insulin-sensitivity-quicki-calculator-324/Quick Referencehttps://nicksterling.com/2025/09/18/quick-reference-guide-tests-for-insulin-resistance-part-1/Spotify Channel:https://podcasters.spotify.com/pod/show/sterlingmdphd/Social & Website:Instagram - https://www.instagram.com/sterlingmdphdX - https://x.com/sterlingmdphdNewsletter - http://eepurl.com/hQpdqTApple Podcasts: https://apple.co/3y438C9This content is not medical advice, is for general information purposes only,and does not constitute the practice of medicine or any other healthcare professional services. No doctor-patient relationship is formed. This content is not a substitute for medical evaluation or treatment and does not take precedence over information provided to you by your healthcare provider or official public health sources. Please visit http://nicksterling.com/terms for full Terms of Use.