10 Longevity Blood Markers Your Doctor Probably Isn't Testing

"Your labs are normal" is among the four most reassuring — and most misleading — words in modern medicine. The annual physical was designed in the 1940s to catch acute disease in a population dying of infections, untreated diabetes, and undiagnosed cancer. It was never designed to optimize human performance, slow biological aging, or detect dysfunction a decade before it becomes diagnosis.

A reference range on a lab report is a statistical artifact — the middle ninety-five percent of values from whoever happened to walk into that lab. That population has a forty-two percent obesity rate and an estimated eighty-eight percent prevalence of metabolic dysfunction. When a patient is told they are "normal," what is actually being said is: "you are similar to the average sick person we test." The longevity-optimal range is structurally different from the population-descriptive range, and the gap between them is where most premature aging hides.

The Gap Between "Normal" and "Optimal"

Consider fasting insulin. The standard reference range at most U.S. labs is 2.6 to 24.9 microIU/mL — a reading of 22 will be flagged green on a patient portal. Yet research from Joseph Kraft, expanded by Catherine Crofts and her collaborators, established that fasting insulin above approximately 5 is already evidence of insulin resistance years before fasting glucose moves. Peter Attia describes fasting insulin as the single most actionable early-warning marker available and targets below 5. The "normal" upper limit is more than four times the longevity target.

The same gap exists across every major longevity marker. Below: the ten markers that consistently separate the patients aging slowly from the patients quietly accumulating risk — and the optimal targets the longevity literature converges on.

The 10 Markers (and Their Longevity-Optimal Targets)

1. ApoB. Target: under 60 mg/dL for aggressive longevity; under 80 for general primary prevention.
   Apolipoprotein B is the protein on the surface of every atherogenic lipoprotein particle — LDL, VLDL, IDL, and Lp(a). One ApoB per particle. Counting ApoB counts the number of artery-damaging particles in circulation. The Mark 2024 meta-analysis confirmed ApoB outperforms LDL-C, non-HDL-C, and LDL particle number as a predictor of cardiovascular events. Attia treats it as his single most-watched cardiovascular number. Most physicians have never ordered it.
2. Lp(a). Target: under 50 nmol/L (or under 30 mg/dL).
   Lipoprotein(a) is 70-90% genetically determined and barely budges with lifestyle. Test once in a lifetime. If elevated, it is not a behavioral problem — it is a genetic risk factor that demands aggressive lowering of every other modifiable cardiovascular variable. Roughly one in five adults is affected and most never learn it.
3. Fasting insulin. Target: under 5 microIU/mL.
   The earliest available marker of metabolic dysfunction. A fasting insulin of 12 with "normal" glucose is a body screaming for help no glucose-based test will detect. Cost to run at Quest: roughly twelve dollars.
4. hsCRP. Target: under 0.5 mg/L.
   High-sensitivity C-reactive protein measures the chronic low-grade inflammation — Claudio Franceschi's "inflammaging" — that is the substrate of nearly every age-related disease: atherosclerosis, type 2 diabetes, Alzheimer's, most cancers, sarcopenia. A reading above 1.0 raises long-term risk of heart attack, stroke, certain cancers, and dementia.
5. Homocysteine. Target: under 7 micromol/L.
   An amino acid that marks methylation dysfunction and predicts both cardiovascular and cognitive decline when elevated. Almost always corrected by methylated B-vitamins (B12 as methylcobalamin, folate as 5-MTHF, B6 as P5P) within 60 to 90 days. Foundational for anyone with a family history of dementia or stroke.
6. IGF-1. Target: lower third of the reference range for adults over 50.
   Insulin-like growth factor 1 is the longevity field's most debated marker — pro-growth in youth, pro-cancer and pro-senescence in mid-life. Attia targets the lower third of the reference range for adults over 50 who have already optimized resistance training and protein intake. Bryan Johnson's published Blueprint values trend toward the lower-middle.
7. Omega-3 Index. Target: above 8 percent.
   The percentage of EPA + DHA in red blood cell membranes. The Framingham follow-up data established it as one of the strongest single-marker predictors of all-cause mortality. Below 4 is associated with the highest mortality; above 8 is the longevity target. Rhonda Patrick has spent a decade publicizing this marker. Intervention: 2-3 grams combined EPA+DHA daily; retest at four months as RBC turnover sets the timeline.
8. HbA1c. Target: under 5.3 percent.
   The three-month average glucose marker — useful but lagging. Pair it with fasting insulin. The standard prediabetic threshold of 5.7 is too lax for longevity work.
9. Triglyceride : HDL ratio. Target: under 1.5.
   A free metric derived from any standard lipid panel that correlates strongly with insulin resistance and the small-dense-LDL pattern. One of the most actionable numbers on the page — and almost never highlighted by primary care.
10. Vitamin D (25-OH). Target: 50-80 ng/mL.
    Genuinely hormonal in function — affects immune regulation, mood, bone, and cardiometabolic risk. The standard "normal" floor of 30 is below the longevity-optimal range.

The Three Testing Stacks

A complete longevity panel is no longer the exclusive province of concierge medicine. Three stacks at three price points:

The comprehensive annual stack ($800-$1,500/year). Function Health publishes one of the most complete longevity-oriented panels available outside a concierge clinic — 102 biomarkers, twice yearly, with a clinician-reviewed dashboard, trend tracking, and a clean consumer interface. It includes ApoB, fasting insulin, hsCRP, full thyroid, full hormonal, NMR LipoProfile, omega-3 index, heavy metals, and core nutrient status. Stack with TruDiagnostic TruAge COMPLETE for annual epigenetic age and DunedinPACE measurement, and a one-month Levels CGM deployment for a targeted metabolic audit. Function Health and Levels are the two cornerstones most data-driven adults converge on.

The budget protocol ($200-$400/year). InsideTracker Essentials or a Quest Direct self-built panel covering the ten markers above, plus a Stelo or Lingo CGM for a one-month annual deployment, plus a free DIY PhenoAge calculation from the standard panel.

The functional medicine path. A longevity-focused MD or DO orders Function-equivalent labs, interprets in clinical context, and prescribes pharmaceuticals where indicated. Cost generally $1,500-$6,000/year via a membership-based concierge model. Telehealth options (Modern Longevity, Lifeforce, Marek Health) have expanded access into the $1,000-$3,000 range.

The Biological Age Layer

Blood markers are inputs. Biological age is the output. In 2011, Steve Horvath at UCLA published the first multi-tissue epigenetic clock — by analyzing methylation patterns across roughly 350 CpG sites, he could predict chronological age with a correlation above 0.96, and the deviation between predicted and actual age was prognostic of mortality.

Three waves followed: chronological-age predictors (Horvath, Hannum), mortality predictors (Levine's PhenoAge 2018, Lu's GrimAge 2019), and rate-of-aging predictors (Belsky's DunedinPACE 2022). A DunedinPACE value of 1.0 means aging one biological year per chronological year. Bryan Johnson's published DunedinPACE reportedly sits in the 0.64-0.69 range — possibly the slowest documented pace in any non-pediatric adult. The Fitzgerald 2021 trial documented an average 3.2-year epigenetic age reduction from an eight-week diet-and-lifestyle intervention. The Fahy 2019 TRIIM trial showed an average 2.5-year reversal over one year using growth hormone + DHEA + metformin.

The practical takeaway: in a six-month focused intervention, a one-to-three year reduction in epigenetic age is realistic for most data-driven adults. The first test sets baseline. The second tests whether the protocol is working.

Closing: The 90-Day Intervention Loop

Single values lie. Trends do not. The discipline that separates longevity-grade data analysis from anxious lab-watching is the rule of trend. The full 90-day intervention playbook — converting an out-of-range marker back into range, deciding when to escalate from behavior to supplement to pharmaceutical, and building a personal dashboard that compounds across years of testing — is laid out in the companion guide.

Decode Your Biology covers the complete framework: the eight markers your annual physical does not measure but should, full head-to-head comparisons of the major biological age tests (TruDiagnostic, Elysium Index, MyDNAge, PhenoAge), three complete testing protocols at three price points, and the 90-day intervention playbook. Available at PureLongevityStore.

This article is part of the PureLongevity research library. For the full deep-dive on every marker, the biological age tests, and the 90-day intervention playbook, see Decode Your Biology on PureLongevityStore. PureLongevityToday may earn a commission from purchases made through links in this article.