Reading Your Lab Panel: What "Normal" Doesn't Mean

Most people get labs done through their primary care physician, receive a report with values flagged either in or out of range, and hear "everything looks normal" if nothing is flagged. That system works reasonably well for screening purposes, for catching overt disease. It doesn't work well for identifying suboptimal function in someone who is technically healthy but not performing the way they should be.

The reference range on a standard lab report answers a specific question: is this value within the distribution seen in the general population? That's not the same question as: is this value consistent with optimal function for this specific person at this age and health status? Performance medicine is interested in the second question. The reference range often can't answer it.

How Reference Ranges Are Built

Standard lab reference ranges are derived from population sampling. A laboratory takes a large group of people, ideally healthy adults, though the selection criteria vary, measures a particular value across that group, and defines the reference range as the interval containing roughly 95% of those values. The bottom 2.5% and top 2.5% fall "out of range."

Two problems emerge from this immediately. First, the reference population isn't necessarily healthy. It's whoever showed up for testing, which often skews older and sicker than you'd want for defining an optimal baseline. Second, and more fundamentally, the range is statistical, not physiological. It tells you where most people fall. It says nothing about where you want to be.

The Values We Pay Close Attention To

Fasting insulin and HOMA-IR. Fasting glucose gets checked routinely. Fasting insulin often doesn't. The problem is that insulin resistance, the reduced ability of cells to respond to insulin's signal, tends to manifest as elevated fasting insulin years or even a decade before fasting glucose rises out of range. A fasting glucose of 94 mg/dL is technically normal. A fasting insulin of 22 µIU/mL alongside it suggests significant insulin resistance that the glucose number alone would completely miss. The ratio of fasting glucose to fasting insulin (HOMA-IR) is a more sensitive early marker than either alone.

IGF-1. Insulin-like growth factor 1 is the primary mediator of growth hormone's anabolic effects. It's what growth hormone signals the liver to produce, and it drives much of the tissue repair, muscle protein synthesis, and metabolic regulation that growth hormone is credited with. IGF-1 declines with age, and a value that falls in the lower third of the reference range for someone's age group is clinically meaningful even if it's technically "normal." In practice, IGF-1 is one of the better proxies for growth hormone axis function and recovery capacity.

SHBG. Sex hormone-binding globulin determines how much of your total testosterone is biologically available. A high SHBG can make a man with a normal total testosterone functionally deficient; a low SHBG can make a man with a borderline low total testosterone actually well within the functional range. Without SHBG, total testosterone is an incomplete number.

Estradiol in men. Most men's panels don't include estradiol, and most primary care physicians don't order it. But in men with visceral adiposity, aromatase, an enzyme concentrated in fat tissue, converts testosterone to estradiol. Elevated estradiol in men is associated with decreased libido, increased fat deposition, emotional volatility, and in some cases gynecomastia. It's also a sensitive indirect marker for metabolic dysfunction. Seeing this number is clinically relevant, and it often tells a story that total testosterone alone doesn't.

DHEA-S. Dehydroepiandrosterone sulfate is produced by the adrenal glands and serves as a precursor to both testosterone and estrogen. It declines with age more steeply than most hormones, by the time someone is in their mid-40s, DHEA-S levels are often half what they were at peak. Suppressed DHEA-S in a younger individual suggests adrenal dysfunction or chronic stress physiology, and it's a variable that often gets missed on routine panels.

hsCRP. High-sensitivity C-reactive protein is a marker of systemic inflammation. Chronically elevated hsCRP, even within the "normal" range but in the upper half, is associated with impaired muscle recovery, insulin resistance, and cardiovascular risk. In a performance context, it tells us something about the inflammatory burden the body is managing, which affects how well everything else works.

Trends Matter as Much as Absolute Values

Single-point measurements are a snapshot. Trends over time tell a more useful story. A testosterone that has gone from 680 to 410 over three years hasn't crossed a reference range threshold; both values are "normal." But the trajectory is telling you something important about what's happening to this person's physiology, and addressing it before it becomes a clinical problem is exactly what performance medicine is designed to do.

This is one of the reasons we build serial monitoring into our protocols. Not to chase numbers, but to understand what's moving, in which direction, and whether the interventions we're using are working.

When we sit down with someone's labs, we're not looking for red flags. We're looking for a coherent story. The individual numbers matter less than what they look like together, whether they paint a picture of a metabolic system under stress, a hormone axis that's flagging, or a recovery capacity that's been quietly declining. That picture is what drives the clinical conversation, and it's a picture the reference ranges alone can't draw.