Male hormone markers
Normal Free Testosterone Levels: Reading the Number That Counts
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20267 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.
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UK labs report calculated free testosterone at about 0.17 to 0.66 nmol/L for adult men, which is 170 to 660 pmol/L. Clinicians treat 0.225 nmol/L as the line worth paying attention to when symptoms are present. Your total testosterone can look normal while this number does not.
Not sure which markers you need? Build your test →You were told your testosterone was normal. You still feel flat, foggy and thirty percent of yourself. Then somebody mentions free testosterone, and none of the numbers on your report seem to match anything you can find online.
This is the number behind that gap. Here is the UK range, what a 0.19 or a 0.40 means, and why one man with a total testosterone of 14 feels fine while another does not.
1. What is a normal free testosterone level in the UK?
North Bristol NHS Trust prints “Adult Males age 18+ years: 0.17 to 0.66 nmol/L”. That is the band most UK labs work to. Other labs report the same thing in picomoles, so 0.17 nmol/L becomes 170 pmol/L. Same number, different decimal point.
| Result | In pmol/L | How it reads |
|---|---|---|
| Under 0.17 | Under 170 | Below the adult range. Worth a repeat morning sample. |
| 0.17 to 0.225 | 170 to 225 | In range, but under the line clinicians watch. |
| 0.225 to 0.66 | 225 to 660 | The bulk of healthy adult men. |
| Above 0.66 | Above 660 | High. Read beside SHBG, albumin and total testosterone. |
If your total testosterone is printed in ng/dL rather than nmol/L, our testosterone unit converter will switch it for you.
2. Why free testosterone can be low when total looks fine
Most of your testosterone is not available to you. It travels through your blood stuck to two proteins: sex hormone binding globulin, or SHBG, and albumin. Only a small slice circulates unattached. That slice is free testosterone.
So the total is the amount in the building. The free fraction is the amount that can get out of the lift.
The European Male Ageing Study measured this in 3,369 men aged 40 to 79. It found 261 of them, near enough one in thirteen, had a normal total testosterone alongside a low free testosterone. Those men were older, had higher SHBG, and reported more of the symptoms that send men for the test in the first place.
“During ageing, total testosterone (TT) declines and SHBG increases, resulting in a greater decline of free testosterone (FT) compared to TT.”
European Male Ageing Study, Archives of Public Health
The authors concluded that free testosterone should be assessed as well as total testosterone in men with symptoms. That is the case for measuring both, from a study of thousands of men. A single total testosterone number is not the whole answer.
3. The thresholds clinicians use
The British Society for Sexual Medicine guidelines say a free testosterone level under 225 pmol/L, or 0.225 nmol/L, “provides supportive evidence” in the presence of appropriate symptoms. The word supportive is doing real work there. It supports a picture. It does not make one.
The European study above drew its own line at 220 pmol/L. The two numbers are close enough that the message is the same. Somewhere around 0.22 nmol/L is where a clinician starts paying attention, and that is well inside the range your lab prints.
What follows a low reading is a medical conversation, not a purchase. Any decision about treatment belongs to your GP or a specialist.
A normal total and a low free number is a common combination, and SHBG is usually behind it. Our guide to high SHBG with a normal testosterone explains the arithmetic.
4. Why SHBG decides your number
Free testosterone is almost never measured directly. North Bristol NHS Trust says it is “calculated in males when testosterone and SHBG are requested together”. Most labs use a formula that takes three inputs: your total testosterone, your SHBG and your albumin.
That has a practical consequence. If a report gives you a free testosterone without an SHBG beside it, something has been estimated rather than calculated. Ask for the workings.
It also explains the man with a normal total and a low free. High SHBG binds more of the hormone, leaving less circulating loose. Ageing, thyroid activity, liver function and low body weight all push SHBG up. Our guide to SHBG levels by age covers that properly.
5. What happens to free testosterone with age?
It falls faster than total testosterone does, and the reason is SHBG. That is the finding quoted above. Total testosterone drifts down with age while SHBG climbs, and the free fraction takes both hits at once.
So two things move at once, in opposite directions, and the free fraction absorbs both. A man of 60 can have the same total testosterone he had at 40 and less of it available.
That is the reason a total-only test can miss the change a man is actually feeling. For the total picture across the decades, read testosterone levels by age.
6. When should you take the sample?
Early. Testosterone peaks in the morning and falls through the day, so an afternoon sample reads low for reasons that have nothing to do with you. North Bristol NHS Trust asks for samples “at 9am due to effects of diurnal variation”.
The BSSM guidelines go further. Testosterone “should be measured between 7 am and 11 am”, and “on at least 2 occasions”. One number never settles this, and a low afternoon reading settles nothing at all.
- Sample between 7am and 11am, ideally around 9am.
- Repeat it on a second morning before drawing conclusions.
- Avoid testing during an illness or right after a hard week of training.
- Keep the timing consistent if you are tracking a change.
7. Which blood test includes free testosterone?
Complete Male Hormones. It measures total testosterone, SHBG and albumin, which are the three inputs the calculation needs, then reports free testosterone and the free androgen index alongside LH, FSH, prolactin and DHEA-S. It is a home finger-prick kit, processed by a UKAS-accredited UK lab.
If you are unsure which fits, the build-my-test tool walks you through it in about a minute. For the other calculated number on the same report, read the free androgen index.
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See the number your total testosterone cannot tell you
Complete Male Hormones measures the three inputs the free testosterone calculation needs, and reports the result with plain-English context. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal free testosterone level in the UK?
North Bristol NHS Trust reports 0.17 to 0.66 nmol/L for men aged 18 and over, which is 170 to 660 pmol/L. Ranges vary slightly by lab, so read your result against the band printed beside it.
Is a free testosterone of 0.24 nmol/L normal?
Yes, it sits inside the 0.17 to 0.66 range, in its lower part. It is also just above the 0.225 nmol/L mark the British Society for Sexual Medicine uses as a point of interest. Read alongside symptoms and a second morning sample.
What free testosterone level is considered low?
Below 225 pmol/L, or 0.225 nmol/L, is the level BSSM guidelines describe as supportive evidence where symptoms are present. The European Male Ageing Study used 220 pmol/L. Both sit inside the printed lab range, which is why the number alone is not enough.
Can free testosterone be low when total testosterone is normal?
Yes, and it is not rare. In 3,369 men aged 40 to 79, the European Male Ageing Study found 261 with a normal total testosterone and a low free testosterone. They were older and had higher SHBG than the men with normal readings for both.
How is free testosterone calculated?
From three measured values: total testosterone, SHBG and albumin. Most UK labs calculate it rather than measuring it directly. If a report shows a free testosterone with no SHBG beside it, ask how it was worked out.
Does free testosterone fall with age?
It falls faster than total testosterone. SHBG rises with age while total testosterone drifts down, and the free fraction takes both hits. That is why a total-only result can look unchanged while the usable amount has fallen.
What time of day should free testosterone be tested?
Between 7am and 11am, and ideally around 9am. Testosterone peaks in the early morning and falls through the day, so an afternoon sample reads artificially low. BSSM guidelines also ask for at least two separate morning measurements.
What is the difference between free testosterone and the free androgen index?
Both estimate how much testosterone is available. The free androgen index is a simpler ratio of total testosterone to SHBG, with no units. Calculated free testosterone uses albumin as well, and is reported in nmol/L or pmol/L.