Testosterone Unit Converter
Testosterone Unit Converter
Convert testosterone between ng/dL, ng/mL and nmol/L, with sex-specific ranges and why the time of sampling changes the answer.
Testosterone converter
Mass ⇄ molarTestosterone 450 ng/dL
Formula and conversion factor
ng/dL = nmol/L ÷ 0.03467
- 0.03467
- derived from the molecular weight of testosterone, 288.42 Da
- ng/mL
- ng/dL ÷ 100
- morning sample
- testosterone must be drawn before about 10am; an afternoon result is not comparable with these ranges
Worked example
Testosterone 450 ng/dL
450 × 0.03467 = 15.60 nmol/L
= 4.50 ng/mL
Reference ranges
| Group | ng/dL | nmol/L |
|---|---|---|
| Men, adult morning sample | 264 – 916 | 9.15 – 31.77 |
| Women, adult | 15 – 70 | 0.52 – 2.43 |
Why the time and method of sampling matter
Testosterone secretion follows a pronounced circadian rhythm, peaking in the early morning and falling by 20–25% by the afternoon. A result drawn at any other time is difficult to interpret against a reference range built from morning samples, so testosterone should always be measured before about 10am, ideally fasting. A low or borderline afternoon result in a man should simply be repeated at 8am before it is acted on at all.
A single low value is never sufficient to diagnose hypogonadism. Guidelines require two low morning samples on separate days, because day-to-day biological variation is substantial and an isolated low result — from acute illness, poor sleep or simply a mistimed draw — is common and does not by itself reflect a fixed state.
Assay choice matters as much as timing. Routine immunoassays are calibrated for the male range and become unreliable at the low concentrations found in women and children, where liquid chromatography-tandem mass spectrometry is the reference method and should be requested whenever the clinical question depends on precision at a low level.
Total testosterone is also a function of sex hormone-binding globulin, not gonadal output alone. Obesity, insulin resistance and nephrotic syndrome all lower SHBG and therefore lower total testosterone while the free fraction stays normal, understating androgen status. Ageing, hyperthyroidism, liver disease and oestrogen therapy raise SHBG and therefore total testosterone, overstating it — in either situation a calculated free testosterone is the more reliable figure.
Frequently asked questions
Why must testosterone be measured in the morning?
Testosterone peaks in the early morning and falls by 20–25% by the afternoon. Reference ranges are built from morning samples, so an afternoon result is not comparable and a low one should be repeated at 8am.
How many low results are needed to diagnose hypogonadism?
Two, both drawn on separate mornings. A single low value is common as an isolated finding and is not diagnostic on its own.
Why is my result unreliable if I'm a woman or a child?
Routine immunoassays are calibrated for the male range and lose accuracy at the low concentrations typical in women and children. Liquid chromatography-tandem mass spectrometry is the reference method in those groups.
Why did my total testosterone change when my weight changed?
Total testosterone tracks SHBG as well as gonadal output. Obesity and insulin resistance lower SHBG and therefore total testosterone even when free testosterone is unchanged — weight loss can raise the total value without a real change in androgen status.
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References
- Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
- Rosner W et al. Position statement: utility, limitations, and pitfalls in measuring testosterone. J Clin Endocrinol Metab. 2007;92(2):405–413.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.