How to Read Your Quest Diagnostics Results for Longevity: A Plain-English Guide

The reference ranges on lab reports like Quest Diagnostics represent the middle 95% of the tested population — not optimal health. Understanding what your results mean for longevity requires different targets. This guide walks through the most important markers and what to look for beyond the flags.

Getting bloodwork back feels like getting a report card where every grade above 40% is called "passing." The reference ranges on most lab reports are designed to identify disease, not optimize health. If you're interested in longevity, you need to know what the numbers actually mean — not just whether they're flagged.

Here's how to read your Quest Diagnostics (or LabCorp — the panels are equivalent) results with a longevity lens.

The Metabolic Panel (CMP / BMP)

Fasting glucose

• Lab normal: 70–99 mg/dL
• Longevity target: 72–85 mg/dL
• Note: Values in the 90s, while technically "normal," reflect impaired insulin sensitivity in the context of a fasting state. Anything above 90 warrants attention to carbohydrate quality and metabolic health.

HbA1c (often on a separate panel — always add this)

• Lab normal: below 5.7%
• Longevity target: below 5.3%
• Note: HbA1c reflects average blood glucose over approximately 90 days. Values of 5.4–5.6% are technically "normal" but indicate metabolic drift. The goal is well below 5.4%.

ALT and AST (liver enzymes)

• Lab normal: ALT <40 U/L, AST <40 U/L
• Note: Elevated ALT in particular is an early sign of non-alcoholic fatty liver disease (NAFLD), which is far more prevalent than most people realize. Values consistently above 25–30 U/L in men, or 20–25 U/L in women, merit attention even when within the "normal" range.

Creatinine and eGFR (kidney function)

• eGFR longevity target: above 90 mL/min/1.73m²
• Note: eGFR naturally declines with age, but values below 90 in younger adults suggest reduced kidney reserve and should be monitored.

The Lipid Panel

LDL-C

• Lab normal: below 100 mg/dL
• Note: LDL-C alone is an incomplete picture. Always look at it alongside ApoB if available. For a deeper explanation of why, see our guide on why your LDL number is misleading you.

ApoB (add this — it's not on a standard lipid panel)

• Longevity target: below 60–80 mg/dL depending on overall risk profile
• Note: This is the most important cardiovascular marker that's missing from standard panels. ApoB tells you the particle count, which is what actually drives atherosclerosis.

Triglycerides

• Lab normal: below 150 mg/dL
• Longevity target: below 80–100 mg/dL
• Note: Elevated triglycerides (even in the 100–149 range) reflect excess carbohydrate intake and insulin resistance. Sub-80 is achievable with dietary optimization and associated with significantly lower cardiovascular risk.

HDL-C

• Lab normal: above 40 mg/dL (men), above 50 mg/dL (women)
• Longevity target: above 60 mg/dL
• Note: Higher HDL correlates with lower cardiovascular risk, but it's not as modifiable as ApoB or triglycerides. Focus on what you can move.

Non-HDL cholesterol

• This is calculated: Total Cholesterol minus HDL. A decent proxy for ApoB if you haven't ordered it.
• Target: below 130 mg/dL

Inflammation Markers

hsCRP (high-sensitivity C-reactive protein — add this)

• Lab normal: below 3.0 mg/L
• Longevity target: below 0.5–1.0 mg/L
• Note: hsCRP is a marker of systemic inflammation. Values above 1.0 mg/L, even in the "normal" range, are associated with increased cardiovascular and all-cause mortality risk. Values above 3.0 mg/L represent elevated risk. Drivers include visceral fat, poor sleep, ultra-processed food diet, and smoking.

Complete Blood Count (CBC)

RBC and Hemoglobin

• Note: Subclinical anemia (slightly low hemoglobin, within the bottom of the reference range) causes significant fatigue and reduced exercise capacity. If your hemoglobin is in the low-normal range and you're tired, investigate.

MCV (mean corpuscular volume)

• Elevated MCV can indicate vitamin B12 or folate deficiency — worth tracking if you're on a plant-based diet or have fatigue.

Hormones and Vitamins

Vitamin D (25-OH)

• Lab normal: 30–100 ng/mL (varies by lab)
• Longevity target: 50–80 ng/mL
• Note: The majority of Americans are below 40 ng/mL. Values below 30 represent frank deficiency. Vitamin D deficiency is linked to immune dysfunction, depression, cardiovascular disease, and cancer risk.

TSH (thyroid-stimulating hormone)

• Lab normal: 0.5–4.5 mIU/L
• Note: TSH above 2.5 mIU/L, while technically normal, may indicate subclinical hypothyroidism worth monitoring — especially if you have fatigue, cold intolerance, or elevated lipids without clear cause.

Testosterone (total and free) — add if relevant

• Low testosterone in men (below 400 ng/dL total) is associated with reduced muscle mass, increased cardiovascular risk, and cognitive decline. Don't ignore this if symptoms are present.

What to Add to a Standard Panel

A standard Quest Diagnostics comprehensive metabolic panel + lipid panel misses several longevity-critical markers. These are worth adding:

1. ApoB — atherogenic particle count
2. hsCRP — systemic inflammation
3. HbA1c — long-term glucose control
4. Vitamin D (25-OH)
5. Omega-3 index (via OmegaQuant or specialty lab)
6. Lp(a) — once in a lifetime; genetic, but good to know

Most of these can be ordered through your physician or directly via services like Marek Health, Walk-In Lab, or LabCorp's direct-to-consumer option. For a broader view of the longevity interventions these markers inform, see The Complete Guide to Longevity.

FAQ

Why are the lab reference ranges so wide?

Reference ranges are derived from the distribution of values in the tested population — typically the middle 95%. This means they reflect what's "average," not what's optimal. In a population with widespread metabolic dysfunction, average and healthy diverge significantly.

My doctor says everything looks fine — but I feel off. What should I do?

Ask your doctor specifically about the markers above that aren't on a standard panel — ApoB, hsCRP, HbA1c, vitamin D. A normal lipid panel with an elevated ApoB or hsCRP looks "fine" by default. You need to specifically order the markers that aren't included.

How often should I get bloodwork for longevity purposes?

Annually as a minimum. If you're actively making dietary, exercise, or supplementation changes, every 3–6 months allows you to track whether your interventions are working.