Understanding Your Labs
Patients are handed lab results every day and told everything looks fine, while they still feel unwell. Often both things are true at once.
A reference range answers a narrow question. Understanding what your results actually mean takes more than a normal or abnormal flag.
The normal range on your lab report is built from a population, and it is usually set so that the middle 95 percent of people tested fall inside it. That means the 2.5 percent at the bottom and the 2.5 percent at the top both land outside “normal” by definition.
It tells you where you sit relative to other people who got tested. It does not tell you where you function best, and those are different questions.
Almost no one is told how these numbers are made, and once you know, a lot of frustrating conversations start to make sense.
A laboratory assembles a group of people it considers healthy. It measures the substance in all of them. Then it takes the middle 95 percent of those results and calls that the reference range. The 2.5 percent at the top and the 2.5 percent at the bottom get labeled abnormal.
That is the whole method, and it is where a great many of the reference ranges on your report come from. It is a statistical description of a group rather than a statement about health.
Not every range is built this way. Some are set by expert consensus or tied to an outcome, which is why you will see different laboratories using different upper and lower cutoffs for the same test. But the middle-95-percent approach is common enough that it is worth understanding what it does and does not tell you.
Three things follow from it, and all three matter to you.
Five percent of perfectly healthy people fall outside the range by definition. Not because anything is wrong with them, but because the math requires it. Run enough tests on a well person and something will come back flagged.
Being inside the range only means you resemble most of the people they measured. It does not mean you are where you function best. Nobody in that process ever asked at what level people feel well, sleep well, hold muscle or think clearly. That question was never part of the exercise.
The reference group is often not much like you. These groups are frequently drawn from blood donors, laboratory staff or whoever was convenient, screened loosely, and defined as healthy largely because nobody had diagnosed them with anything. People with quiet, undiagnosed disease sit inside that group and pull the range toward illness. It is also why two laboratories can report different ranges for the same test.
And because the reference population is drawn from the population at large, the range drifts as that population does. As a country gets heavier and more metabolically unwell across decades, what counts as normal follows it down. Normal is a moving target, and it tracks the health of the sample rather than health itself.
Some reference ranges are not merely broad, they are clinically unhelpful. The reported lower limit for free testosterone in women can approach zero, which is not a meaningful floor for a hormone that drives energy, libido, mood and muscle.
A result inside a range like that tells you almost nothing.
Most ranges are not adjusted for age, and that produces errors in both directions.
A 40-year-old man with a testosterone at the very bottom of the adult range may sit in the lowest few percent of healthy men his age, and be told he is fine. Apply that same number to a 72-year-old and it is unremarkable. Same value, opposite conclusions.
Most of your sex hormones circulate bound to a carrier protein called sex hormone binding globulin, and while bound they cannot enter cells or do anything.
SHBG rises with age and with thyroid overactivity. It falls with obesity and insulin resistance. So two people with identical total testosterone can have very different amounts actually available, and the one with high SHBG can have real symptoms while being told everything is normal.
Hormones operate as a connected system with feedback loops and conversion pathways. LH and FSH can tell you whether a problem sits in the gland itself or in the signal coming from above it. Thyroid and prolactin can sometimes help explain the whole picture when nothing else does.
Reading one number out of context is the most common reason symptomatic patients get told they are fine while something treatable goes unaddressed.
Complex hormonal, metabolic and urologic second opinions are welcome.
Urology is a wider specialty than most people realize. It deals with the adrenal gland, the parathyroid, the hypothalamus, the pituitary and the gonads, which are all endocrine organs. Add three decades of work in hormones, sexual medicine and metabolic health on top of that, and you end up fluent in several systems that are usually read in isolation by different people.
Medicine has become extremely specialized, and mostly for good reasons. The trade is that each physician tends to look hard at their own area and take everything outside it as background. Your results get read in slices by people who never compare notes, and a pattern that spans three of those slices can pass through all of them unnoticed.
Starting from the symptom rather than the specialty changes what you see. If someone is exhausted, the question is not whether the thyroid panel is normal in isolation. It is which combination of results could produce that exhaustion, and how they relate to each other.
That matters because a panel is not a list of separate results. Thyroid affects binding proteins, which change how much testosterone is actually available. Insulin resistance lowers those same binding proteins and raises conversion in fat tissue. Fat tissue is an organ in its own right, and it converts androgens into estrogens: testosterone into estradiol, and androstenedione into estrone, the pro-inflammatory one. Cortisol suppresses the signal from the brain to the gonads. Iron and vitamin D sit underneath fatigue that gets blamed on hormones.
Read one number at a time and each looks unremarkable. Read them together and a pattern usually appears. Being able to do that across urologic, endocrine, hormonal and metabolic results in the same sitting is the single most useful thing I bring to a complicated set of labs.
Knowing that a reference range answers the wrong question is only useful if you have something better to compare against.
I have partnered with Labstro to build exactly that: a clear, readable interpretation of complex laboratory work that reports results against optimal values rather than only the standard reference range. Same result, two lines. Where you sit relative to the population, and where you sit relative to where people actually function well.
Optimal ranges are interpretive. They come from the published literature, from clinical experience, and from judgment, and they carry more uncertainty than a laboratory range does. I would rather say that plainly than pretend otherwise. What they are not is a number pulled out of the air, and what they do is give a starting point for a conversation that a normal-abnormal flag cannot.
Direct answers first. The details follow.
If you still have a regular period, timing changes what the numbers mean, so it matters. Estradiol starts low during your period, climbs through the first half of the cycle, and peaks just before ovulation at midcycle. Progesterone stays near zero until after ovulation, then peaks about a week before your next period. So the classic timing is days 2 to 4 of your cycle for baseline estradiol, FSH and LH, and around day 19 to 21 to catch progesterone at its height. Testosterone changes far less across the month and can be drawn any time, ideally in the morning. Two things outrank the calendar: if your periods are irregular or gone, draw whenever, and if the goal is to explain your symptoms, drawing when you feel your worst tells us the most. Whoever orders the labs needs to know where in the cycle you were, because the same number can be normal on day 3 and telling on day 21.
The usual lab cutoff sits near 300 ng/dL, but the cutoff is where thinking starts, not where it ends. Reference ranges are built from the middle 95 percent of people tested, which tells you where you sit among other men who got tested, not where you function best. A man can be technically normal and functionally low, especially when SHBG is high and free testosterone is scarce. Symptoms, free testosterone and repeated morning draws together make the call. A single number compared to a range does not.
Total testosterone counts everything in the blood, but most of it is handcuffed to a protein called SHBG and unavailable to your tissues. Free testosterone is the small unbound fraction actually doing the work. SHBG is the protein doing the binding, and it moves: thyroid problems raise it, insulin resistance lowers it, and age drifts it upward. Two men with identical totals can live in different bodies because their SHBG differs. This is why I never interpret a total testosterone alone, and why panels beat single values.
Hormones run on schedules. Testosterone peaks early and falls through the day, so an afternoon draw can make a normal man look deficient. Cortisol has its own curve. And every hormone bounces day to day, which is why a single result, high or low, is a data point rather than a diagnosis. Repeating a morning draw before making any treatment decision is not bureaucracy. It is the difference between treating a pattern and treating a coincidence, and I will not start therapy on a coincidence.
When you have real symptoms and keep being told everything is normal. When each specialist has reviewed only his own slice and nobody has read the whole panel as one system. When a number sits at the edge of the range and the plan is to wait until it crosses a line. Complex hormonal, metabolic and urologic second opinions are a significant part of my practice precisely because panels are usually read in isolation. The results connect to each other. Someone should read them that way.
Last medically reviewed August 2026 by Roscoe S. Nelson, MD, FACS, board-certified urologist.
Peri Health & Hormones is where Dr. Nelson provides current clinical care in hormones, metabolic health, sexual health, recurrent UTI and selected procedures.
807 E. Pioneer Rd. Suite 105
Draper, UT 84020
Straight answers. No hype. Just practical information you can use.
