Overview
Two things make this question harder to answer than it looks.
Reference ranges vary substantially between laboratories — different assays, different reference populations, and some labs age-adjust while others do not. A result flagged low at one lab can be unremarkable at another.
And the diagnosis is not made from a number. Guidelines are consistent: testosterone deficiency requires consistently low levels on at least two morning samples, plus symptoms. A low number without symptoms is not a diagnosis, and symptoms without a low number are not treated with testosterone.
| What it does | Why it matters | |
|---|---|---|
| Total testosterone | Everything in circulation, bound and free | The screening test. Morning sample, fasting, repeated if low |
| Free testosterone | The unbound, active fraction | Matters most where SHBG is abnormal — which is common after 45 |
| SHBG | Binds most circulating testosterone | Changes what the total means. Rises with age |
| LH and FSH | Pituitary signals | Separate a testicular cause from a pituitary one |
| Age adjustment | Some labs apply it, some do not | Ask which yours uses before interpreting a flag |
What actually declines with age: total testosterone falls gradually — roughly one to two percent per year after about 30 in most men. SHBG rises at the same time, so free testosterone falls faster than total does. Which is why a man with a "normal" total can still have a genuinely low free level, and why total alone can miss it.
Why the ranges disagree
Reference ranges are built from a measured population, so who is in that population determines the range.
Some laboratories derive theirs from healthy young men. Others use a broad adult male sample that includes older men — which shifts the range downward, because it includes the decline being measured. A few apply explicit age bands.
Add genuine assay variation between platforms, and results are not always comparable between laboratories. If you are tracking testosterone over time, tracking it at the same lab is worth more than a technically better result elsewhere.
Efforts to standardize male reference ranges have been under way for years, and progress is real but incomplete. In practice: check whether your lab age-adjusts, and read the flag against the range printed on your own report rather than against a number you read somewhere.
Why the sample conditions matter this much
Testosterone is not a stable value through the day, and the conditions under which it is drawn change the result enough to change the conclusion.
Time of day. Testosterone follows a daily rhythm, peaking in the morning and falling through the day. The difference between an 8am and a 4pm sample in the same man can be substantial. Morning collection is standard, and an afternoon result that looks low frequently is not.
Fasting. Eating lowers testosterone acutely, so samples are generally taken fasting.
Acute illness and recent significant stress lower it, which is why a result taken during or shortly after illness is repeated rather than acted on.
Repeat testing. Because of all of the above, guidelines call for at least two separate morning samples before a diagnosis. A single low result is a reason to repeat, not a reason to treat.
That sequence is skipped constantly in this market, and it is the most common reason men end up on treatment they did not need.
SHBG, and why free testosterone matters after 45
Most circulating testosterone is bound to sex hormone binding globulin and is not available to tissue. Only the free fraction is active.
SHBG rises with age, which means an older man's total testosterone overstates how much is actually available to him. Two men with the same total can have quite different free levels.
SHBG also moves for other reasons: it rises with age, thyroid overactivity and liver disease, and it falls with insulin resistance, obesity and some medications. So a man with insulin resistance may have low SHBG, a low-looking total testosterone and a perfectly adequate free level — a picture that reads as deficiency and is not.
Which is why total testosterone is read alongside SHBG rather than alone. What SHBG does and what moves it.
Free testosterone is best calculated from total and SHBG, or measured by specific methods. Direct analog immunoassays for free testosterone are widely available and widely regarded as unreliable — worth asking which method your result came from.
What a low result should trigger
Not a prescription. An assessment.
Repeat the test — a second morning sample, fasting, not during illness.
Add SHBG, so free testosterone can be estimated.
Check LH and FSH, which separate a testicular cause from a pituitary one. That distinction changes management substantially and is frequently skipped.
Check prolactin where LH is low, because raised prolactin has specific causes that need identifying.
Look for reversible contributors, which is the part most often missed: obesity, which lowers testosterone and improves with weight loss; obstructive sleep apnea, which suppresses it and is heavily under-diagnosed; alcohol; opioids, which suppress the axis directly; some medications; and acute or chronic illness.
Several of those are treatable in their own right, and treating them sometimes resolves the testosterone question entirely. Starting testosterone instead leaves the underlying problem in place — and if the man wants children later, that matters more than it first appears. How the alternatives differ.
What we would not conclude
We would not diagnose deficiency from one afternoon sample.
We would not treat a level in the lower part of the range in a man without symptoms, because there is no evidence that doing so benefits him.
And we would not present age-related decline as a disease. Testosterone falls gradually with age in most men, that is expected, and the question is whether a given man has symptoms attributable to it — not whether his number is lower than it was at 25. The general version of this argument.
Frequently asked questions
What is a normal testosterone level for my age? It depends on your laboratory's range and whether it age-adjusts. More usefully: the diagnosis requires consistently low morning levels plus symptoms, not a number alone.
Why does the time of day matter? Testosterone peaks in the morning and falls through the day. An afternoon sample can read substantially lower in the same man, which is why morning collection is standard.
Do I need free testosterone as well as total? Usually yes after 45, because SHBG rises with age and changes what the total means. Ask which method was used — direct free testosterone immunoassays are considered unreliable.
My level is low but I feel fine. Do I need treatment? A low level without symptoms is not an indication for treatment. It is a reason to repeat the test and look for a cause.
Can anything raise it without medication? Sometimes substantially — treating sleep apnea, reducing weight, reviewing opioids and alcohol, and treating illness all affect it. These are worth addressing regardless.
Where this fits in your plan
The useful version of this question is not "what is normal for my age." It is whether you have symptoms, whether repeated morning testing confirms a low level, and whether something reversible is driving it.
That is a panel and a conversation rather than a number — total and free testosterone with SHBG, LH and FSH, plus the things that suppress it. What we check.
We measure first. Then we act.
Diagnostic testing does not diagnose or rule out disease on its own and is interpreted by a licensed provider alongside your history and examination.
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This article is educational and is not medical advice. Treatments are available only to eligible patients following clinical evaluation and within applicable regulations. Individual results vary.
