Hormones and units
Testosterone ng/dL to nmol/L: UK Conversion
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed July 20266 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
QUICK ANSWER
UK labs report testosterone in nmol/L; US sites use ng/dL. To convert ng/dL to nmol/L, multiply by 0.0347. To go the other way, multiply nmol/L by 28.8. A total testosterone of 15 nmol/L is about 432 ng/dL, which sits in the healthy range for an adult man.
Want your own number, in the right units? Build your test →As of July 2026.“Is my testosterone low?” is one of the most-searched men's health questions in the UK. Half the confusion is not the level. It is the units.
You get a UK result of 14. Then you read a US forum where 300 is “low.” The numbers look worlds apart. They often are not.
This guide shows the exact conversion, gives you a quick table, and explains what actually counts as low in both units.
1. Why does my result look different online?
The hormone is the same everywhere. The units change by country. UK and most European labs report testosterone in nanomoles per litre (nmol/L). US labs, and most TRT forums, use nanograms per decilitre (ng/dL).
So a US “normal” of 500 sits right next to a UK result of 17. They look nothing alike. They are the same number in different clothes.
This trips up a lot of men. You read that 300 ng/dL is the US cut-off for low testosterone. Your UK result says 14. Is that good or bad? The answer is simple once you convert.
2. How do I convert ng/dL and nmol/L?
There are two factors. Both come from the molar mass of testosterone, which is 288.42.
- ng/dL to nmol/L: multiply by 0.0347.
- nmol/L to ng/dL: multiply by 28.8.
Two worked examples. A US result of 500 ng/dL, times 0.0347, is 17.4 nmol/L. That is healthy. A UK result of 12 nmol/L, times 28.8, is 346 ng/dL. That is the low end of the US “normal” band.
One caution. These factors work for total testosterone. Free testosterone is reported in smaller units, usually pmol/L in the UK or pg/mL in the US, and uses a different scale. Our free vs total testosterone guide covers that number.
3. Quick reference table (total testosterone)
Keep this handy when you read a result. The values are rounded.
| nmol/L (UK) | ng/dL (US) | Rough read |
|---|---|---|
| 8 | 230 | Likely deficient (BSSM) |
| 10 | 288 | Grey zone |
| 12 | 346 | Grey zone, upper edge |
| 15 | 432 | Healthy |
| 20 | 576 | Healthy |
| 25 | 720 | Healthy, high side |
To convert any other value, use the two factors above. For a full breakdown of ranges by decade, see our testosterone levels by age guide.
4. What counts as low or normal?
UK practice does not treat testosterone as one hard line. It uses bands. The British Society for Sexual Medicine sets the thresholds most UK clinicians follow.
“A total testosterone level lower than 8 nmol/L usually requires treatment. A level higher than 12 nmol/L does not.”
— British Society for Sexual Medicine (BSSM) guidelines, paraphrased
In plain terms, that gives three bands.
- Below 8 nmol/L (about 230 ng/dL): likely low, and symptoms usually warrant a review.
- 8 to 12 nmol/L (about 230 to 346 ng/dL): a grey zone. Here BSSM advises measuring free testosterone before deciding.
- Above 12 nmol/L (about 346 ng/dL): usually normal on the total number alone.
Two things matter here. First, a single low reading is not a diagnosis. Testosterone should be measured in the morning, and confirmed on a second sample. Second, the total number is only half the story. When you sit in the grey zone, free testosterone and SHBG decide the rest. Our guide on borderline testosterone walks through what to do next.
A blood test measures biomarkers and offers wellness insight. It does not diagnose a condition. If your result worries you, that is a conversation for a qualified clinician.
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Stop converting other people's numbers
The clearest way to end the unit confusion is to see your own result in nmol/L. Helvy's Complete Male Hormones panel measures total and free testosterone, SHBG, LH, FSH, prolactin and DHEA-S in one home finger-prick test, run by UKAS-accredited UK laboratories, with results in around 5 working days.
Frequently asked questions
Is 300 ng/dL low testosterone in the UK?
300 ng/dL is about 10.4 nmol/L. In UK practice that sits in the grey zone between 8 and 12 nmol/L, not clearly low. BSSM advises measuring free testosterone before making any decision. Symptoms and a repeat morning test matter as much as the single number.
What is 15 nmol/L in ng/dL?
About 432 ng/dL. You multiply the nmol/L value by 28.8. A level of 15 nmol/L is comfortably in the healthy range for an adult man.
Why does the UK use nmol/L and the US use ng/dL?
The UK and most of Europe report lab values in SI units, which count molecules (moles). The US uses mass units (grams). Both describe the same hormone. Neither is more accurate; they are just different scales.
Which testosterone number should I trust?
Use the number in the units your own lab reported, and read it against a UK reference range. Convert US figures only to compare. And do not judge low T on total testosterone alone; free testosterone and SHBG complete the picture.
How do I test my testosterone at home in the UK?
A home finger-prick panel collected in the morning covers it. Helvy's Complete Male Hormones panel measures total and free testosterone, SHBG, LH, FSH, prolactin and DHEA-S, and reports in nmol/L. Results come back in around 5 working days from UKAS-accredited UK laboratories.
Related guides
Testosterone Levels by Age (UK)
Normal ranges by decade in nmol/L, plus the BSSM thresholds.
Free vs Total Testosterone
Why a normal total can still mean low T, and the SHBG trap.
Borderline Testosterone
What to do when your result lands in the 8 to 12 nmol/L grey zone.
Testosterone Blood Test UK
What is measured, when to test, and how to read the result.