Testosterone levels by number

What your testosterone number means

A converter turns one number into another number. It does not tell you the thing you actually wanted to know, which is whether the result is a problem. The bands below do that, using the CDC-standardised harmonised reference range as the yardstick rather than any single lab's interval.

Range boundaries from Travison et al., JCEM 2017 (CDC-standardised, healthy non-obese men aged 19–39). The internal splits at 400 and 600 ng/dL are descriptive conveniences, not guideline cut-offs. Bands describe total testosterone in adult men only.

Is my level low for my age?

Two different things get conflated here, and separating them answers the question. The population average falls with age: total testosterone declines on the order of 1 to 2 percent per year from roughly age 30 to 40 onward, so an older man is more likely to sit low in the range. The diagnostic threshold does not fall with age: the Endocrine Society's 2018 guideline applies the same 264 ng/dL cut-off at any adult age, on the reasoning that a level being common in older men does not make it benign.

The practical consequence: a 60-year-old at 350 ng/dL (12.1 nmol/L) is below the midpoint for men aged 19–39 and still above every guideline threshold. Whether that is worth treating is a symptoms-and-history question, not an arithmetic one.

Free testosterone: the range depends on how it was measured

Free testosterone is the one value where the reference interval genuinely cannot be generalised, and the reason is worth understanding before you compare your number to anyone else's.

• Direct analog immunoassay typically reports adult male free testosterone around 6–22 pg/mL.
• Equilibrium dialysis and calculated free testosterone typically report around 50–210 pg/mL for the same men.

That is close to a tenfold difference in the number for an identical sample. It is not that one is wrong; they are measuring different things and reporting both as “free testosterone”. The practical rules that follow: read your free T against the interval printed on your own report, never against a forum number, and never compare a free T from one method to a free T from another. Free testosterone is roughly 1 to 3 percent of total in most men, and calculating it from total T, SHBG and albumin is a reasonable substitute when a measured value is not available.

Quick conversion table

The values people most often need, both directions. 264 ng/dL and 12 nmol/L appear because they are guideline thresholds rather than round numbers. Every one of them is interpreted individually further down.

Every common result, converted and interpreted

The conversion is the easy half. Each entry below gives the number in both unit systems and then the part a converter cannot tell you: where that value sits against the harmonised reference range and the three guideline thresholds. Bands are for total testosterone in adult men; free testosterone and estradiol are handled separately above.

Results reported in ng/dL

Results reported in nmol/L

Bands follow the CDC-standardised harmonised reference range for healthy non-obese men aged 19–39 (264–916 ng/dL, 9.2–31.8 nmol/L; Travison et al., JCEM 2017). “Above the reference range” and “supraphysiological” describe levels higher than that population reaches without treatment; they are not a diagnosis. Your own lab prints its own interval, which may differ.

All hormone conversion factors

Every factor below is derived from molecular weight, so they are exact rather than estimated. The commonest error on this table is not the arithmetic - it is reading the wrong unit off the lab report in the first place.

Reference ranges and guideline thresholds

These are not the same thing, and conflating them causes a great deal of unnecessary worry. A reference range describes what is typical in a healthy population. A diagnostic threshold is where a guideline body suggests investigating - a policy decision informed by that data, not a fact derived from it.

Ranges converted here for convenience; each source publishes in its own unit system. Your own lab will also print its own reference interval, which may differ from all of these because it reflects that lab's assay and its own reference population.

Why two labs disagree when the maths does not

The conversion is fixed arithmetic, so when two results seem irreconcilable the cause is somewhere else. Four candidates, roughly in order of how often they are the culprit:

• Time of day. Testosterone follows a diurnal rhythm, peaking in the morning. This is why guidelines specify a morning draw, and why an afternoon result is not comparable to a 8am one from a month earlier.
• Assay platform. Immunoassay and LC-MS/MS measure differently. The gap is most consequential for estradiol in men and for free testosterone, where a "sensitive" assay is generally the one worth having.
• Calculated vs measured free T. Many reports calculate free testosterone from total T, SHBG and albumin rather than measuring it. Different calculation methods give different answers from identical inputs, so a calculated value and a measured one are not interchangeable.
• Where you are in the injection cycle. On an injected protocol the level is a moving curve, not a fixed number. A trough draw and a peak draw from the same protocol can differ by a factor of two or more - which is exactly why when you drew the blood is as important as the number it produced.

None of these are errors in the lab work. They are the reason a single number is a poor basis for a decision, and a trend measured consistently is a much better one.

Frequently asked questions

Is 300 ng/dL low testosterone?

It depends on which guideline is applied, which is why the question has no single answer. 300 ng/dL (10.4 nmol/L) is the American Urological Association's diagnostic threshold exactly, so it is borderline by the AUA. It is above the Endocrine Society's 264 ng/dL cut-off, so it is not low by that guideline. It is below the European Association of Urology's 12 nmol/L (about 346 ng/dL), so it is low by that one. It also sits inside the CDC-standardised harmonised reference range of 264–916 ng/dL, in its bottom quarter. In practice a result of 300 warrants a second morning draw before anything is concluded, because day-to-day variation of 20 to 30 percent is ordinary.

Is 15 nmol/L a normal testosterone level?

15 nmol/L is 433 ng/dL, which is inside the harmonised reference range of 9.2–31.8 nmol/L and above all three guideline thresholds (Endocrine Society 9.2, AUA 10.4, EAU 12 nmol/L). It sits a little below the middle of the healthy distribution for men aged 19 to 39. Symptoms at this level are common and are usually worth investigating through free testosterone, SHBG, thyroid and sleep rather than through total testosterone alone.

What is a normal free testosterone level?

There is no harmonised free testosterone range, and the honest answer is that the normal interval depends on how the lab measured it. Direct analog immunoassays typically report adult male free testosterone around 6–22 pg/mL, while equilibrium dialysis and calculated free testosterone typically report around 50–210 pg/mL for the same men. That is close to a tenfold difference in the number for an identical sample, so a free testosterone result is only interpretable against the reference interval printed by the lab that produced it, and free testosterone values from two different methods cannot be compared at all. Free testosterone is roughly 1 to 3 percent of total testosterone in most men.

Why do labs disagree on reference ranges?

Because a reference range is not a fact about testosterone, it is a description of a particular population measured on a particular assay. Each lab derives its interval from its own reference population and its own analytical platform, and immunoassay and LC-MS/MS do not return identical values on the same sample. That is precisely why the CDC-standardised harmonised range from Travison et al. (JCEM, 2017) exists: it gives a common yardstick of 264–916 ng/dL that is independent of any one lab. Guideline thresholds are a separate thing again, being policy decisions about when to investigate rather than statements about what is typical, which is why the Endocrine Society, the AUA and the EAU can all publish different cut-offs without any of them being wrong.

What testosterone level is considered high or supraphysiological?

The harmonised reference range for healthy non-obese men aged 19 to 39 tops out at 916 ng/dL (31.8 nmol/L), so results above roughly 900–1,000 ng/dL are above what that population reaches untreated. Levels beyond about 1,200 ng/dL (41.6 nmol/L) are described as supraphysiological, meaning higher than the testes produce unaided. On an injected protocol a high reading very often reflects when the blood was drawn rather than the dose, since a peak draw and a trough draw from the same protocol can differ by a factor of two or more.

Does a normal testosterone level change with age?

The population average falls, but the diagnostic threshold does not. Total testosterone declines on the order of 1 to 2 percent per year from around age 30 to 40, which is why an older man is more likely to sit in the lower part of the range. The Endocrine Society's 2018 guideline nonetheless applies the same 264 ng/dL cut-off at any adult age rather than an age-adjusted one, on the grounds that a level being common in older men does not make it harmless. So a 60-year-old at 350 ng/dL is below the midpoint for men aged 19 to 39 and still above every guideline threshold.

How do I convert testosterone from nmol/L to ng/dL?

Multiply nmol/L by 28.84. So 12 nmol/L is about 346 ng/dL, 15 nmol/L is about 433 ng/dL, and 20 nmol/L is about 577 ng/dL. Going the other way, multiply ng/dL by 0.0347. The factor comes from testosterone's molecular weight of 288.42 g/mol - it is fixed arithmetic, not an approximation, so the conversion itself is never the source of disagreement between two results.

Why does my UK lab report nmol/L when US forums use ng/dL?

They are the same measurement in different unit systems. Most of Europe, the UK, Australia and Canada report in SI units (nmol/L), while the United States mostly uses conventional mass units (ng/dL). Neither is more accurate. This is the single biggest source of confusion in international TRT discussions: someone reporting '15' and someone reporting '433' may have identical testosterone levels.

What is a normal testosterone level?

The most defensible modern answer is the CDC-standardised harmonised range from Travison et al. (JCEM, 2017): 264-916 ng/dL, or roughly 9.2-31.8 nmol/L, in healthy non-obese men aged 19-39. Guideline diagnostic thresholds differ from that range and from each other - the Endocrine Society uses 264 ng/dL, the AUA uses 300 ng/dL, and the EAU uses 12 nmol/L (about 346 ng/dL). A result can therefore be 'low' by one guideline and 'normal' by another without anyone being wrong.

How do I convert estradiol from pg/mL to pmol/L?

Multiply pg/mL by 3.67. So 30 pg/mL is about 110 pmol/L. To go back, multiply pmol/L by 0.272. Note that the conversion is the easy part of estradiol - the harder issue is assay type. A standard immunoassay and an LC-MS/MS 'sensitive' estradiol assay can return substantially different numbers on the same sample, and in men the sensitive assay is the one generally considered reliable.

Can I compare two results from different labs?

Only with care, and unit conversion is the smallest part of it. Different assay platforms measure testosterone differently, and each lab publishes its own reference interval - which is why the harmonised CDC-standardised range exists as a common yardstick. If you are tracking a trend over time, using the same lab and the same assay matters more than any single number, as does keeping the draw time consistent, since testosterone follows a diurnal rhythm and morning draws are the convention.

Does the conversion factor change for free testosterone?

The molecular weight is the same, but the units usually are not. Free testosterone is typically reported in pg/mL rather than ng/dL, so the factor to pmol/L is 3.467. If your lab reports free testosterone in ng/dL, multiply by 34.67 to get pmol/L. Check which unit is on your report before converting - mixing up pg/mL and ng/dL is a factor-of-100 error and by far the most common mistake on this particular value.

Sources & further reading

• Travison TG et al., Harmonized reference ranges for circulating testosterone levels in men (JCEM 2017) - source of the CDC-standardised 264–916 ng/dL range
• Bhasin S et al., Testosterone therapy in men with hypogonadism - Endocrine Society Clinical Practice Guideline (2018)
• AUA Guideline - Testosterone Deficiency (300 ng/dL diagnostic threshold)
• EAU Guidelines - Sexual and Reproductive Health (12 nmol/L threshold)
• CDC Hormone Standardization Program (HoSt) - why assay standardisation is needed for cross-lab comparison
• OptiPin tools: free testosterone calculator · bloodwork guide · free vs total T · forecast methodology

Conversion factors are computed from molecular weights (testosterone 288.42, estradiol 272.38, DHT 290.44 g/mol) rather than copied from secondary sources, so they can be re-derived rather than taken on trust. Guideline thresholds are quoted as published and linked to their source; where guidelines disagree we have shown all of them rather than picking one.

Not medical advice. This is a unit-conversion reference. Interpreting a hormone result requires clinical context this page does not have - symptoms, history, timing, assay, and repeat testing. Do not start, change, or stop treatment based on a converted number.