If you have ever looked at a blood test result and seen your testosterone reading, you might have noticed that "normal" covers an enormous range. Different labs use different units, different cut-offs, and different definitions of what counts as low. The result is that men often walk away from their GP being told their levels are "fine" while still feeling exhausted, foggy, and disconnected from themselves.
This article explains what normal male testosterone levels actually look like, why the standard ranges are misleading on their own, and how to interpret your results in a way that connects to how you feel.
The numbers, simply
Testosterone in the UK is typically measured in nanomoles per litre (nmol/L). In the US, it is more commonly measured in nanograms per decilitre (ng/dL). The two are interchangeable but the numbers look very different.
The typical UK reference range for total testosterone in adult men runs from around 8.6 to 29 nmol/L. That is a huge range. The same range expressed in US units would be roughly 250 to 850 ng/dL.
The British Society for Sexual Medicine (BSSM) guidelines for UK clinical practice generally consider:
- Above 12 nmol/L: usually fine, treatment rarely indicated unless symptoms are very strong
- Between 8 and 12 nmol/L: a grey zone where treatment may be considered if symptoms are significant
- Below 8 nmol/L: clinically low, treatment usually appropriate if symptoms are present
These are simplifications, and individual clinical judgement matters. A man at 9 nmol/L with severe symptoms is a different case from a man at 9 nmol/L who feels fine.
Testosterone levels by age: normal ranges for men
Testosterone declines with age, but more slowly than people often assume. The average drop is around 1-2 percent per year after age 30, though individual variation is huge.
The best reference data we have comes from a 2017 study in the Endocrine Society's journal that pooled four large cohorts and re-measured testosterone with a single calibrated method, so the numbers are comparable. The table below is that study's reference range for healthy, non-obese men by age band, with the median alongside. UK labs report in nmol/L; I've added ng/dL because most of what you'll read online uses American units (1 nmol/L is 28.84 ng/dL).
| Age | Typical range (nmol/L) | Median (nmol/L) | Typical range (ng/dL) |
|---|---|---|---|
| 19 to 39 | 9.3 to 32.2 | 18.4 | 267 to 929 |
| 40 to 49 | 8.1 to 32.2 | 16.7 | 235 to 929 |
| 50 to 59 | 7.6 to 32.2 | 16.5 | 219 to 929 |
| 60 to 69 | 7.6 to 32.2 | 16.5 | 218 to 929 |
| 70 to 79 | 7.6 to 32.1 | 16.5 | 218 to 926 |
| 80 to 99 | 5.4 to 31.7 | 16.5 | 157 to 913 |
Two things stand out. The upper end barely moves with age, and in this dataset the median is fairly flat from 40 onwards too. What falls is the bottom of the range: the lowest 2.5 percent of healthy 50-year-olds sit well below the lowest 2.5 percent of healthy 25-year-olds. Ageing itself lowers testosterone less than people assume. Weight, sleep, illness and medication do a lot of the damage that gets blamed on birthdays, which is one reason men in their 40s and 50s with low numbers shouldn't be told it's just their age.
The rounded figures I've quoted in clinic for years are below. They're broad averages drawn from mixed population data, so they sit a little lower than the harmonised cohort above, which only included healthy men who weren't obese:
- Late teens to mid-20s: 18-25 nmol/L
- 30s: 16-22 nmol/L
- 40s: 14-20 nmol/L
- 50s: 12-18 nmol/L
- 60s and beyond: 10-16 nmol/L
These are averages, not targets. Plenty of healthy 60-year-olds have testosterone levels of 20+ nmol/L. Plenty of 30-year-olds have levels in the low teens. Your individual context, symptoms, and history matter more than averaging.
The trend, though, is worth noting. Population averages for testosterone have declined over recent decades. The numbers above are based on current population data, which means today's averages are lower than they were 40 years ago. A 50-year-old in 1985 might have averaged levels closer to today's 30-year-olds.
Reference range versus treatment threshold
A reference range tells you where healthy men's levels fall. It isn't a treatment threshold, and it isn't adjusted for age in UK practice. The thresholds UK doctors actually use come from the British Society for Sexual Medicine, whose 2023 guideline says a total testosterone below 12 nmol/L, or a free testosterone below 0.225 nmol/L, measured on two separate morning samples taken between 8 and 11am, usually warrants treatment where symptoms fit, and that the best responses in sexual symptoms are seen in men who start below 8 nmol/L. Levels between 8 and 14 nmol/L may justify a trial of treatment of at least six months, based on symptoms.
That's where the two numbers you'll hear most often come from. In our guide to how low testosterone is diagnosed in the UK we put it like this: below 8 nmol/L on two separate samples is deficiency, 8 to 12 is the grey zone where free testosterone and symptoms decide, 12 to 15 is still treatable at a clinician's discretion where symptoms are significant, and above 15 deficiency is unlikely and something else is probably going on.
Notice that these thresholds don't change with age. A 55-year-old at 9 nmol/L is in the grey zone, not "normal for his age", even though 9 nmol/L is inside the reference range for his decade. If your total testosterone is borderline, the free testosterone figure is what settles it, and you can work yours out from total testosterone, SHBG and albumin with our free testosterone calculator.
Why the "normal" range is misleading
The range your lab quotes (often something like 8.64 to 29 nmol/L) is what is called a population reference range. It is built by measuring thousands of men, taking the middle 95 percent of the distribution, and calling that "normal."
The problem is twofold. First, "normal" in a statistical sense is not the same as "optimal." A reading at the very bottom of the range (say, 9 nmol/L) is technically within normal limits, but it is a level associated with significant symptoms in many men. Most men feel best somewhere in the middle to upper portion of the range.
Second, the population used to set the reference range includes men with declining testosterone due to age, obesity, chronic illness, and other factors. As average male testosterone levels have dropped over recent decades, the "normal" range has effectively become a lower bar than it was a generation ago. What is statistically normal today may not be biologically optimal.
In practice, this means a result of 10 nmol/L might be reported back to you as "normal" when in fact it sits at a level where many men report symptoms and would benefit from intervention.
Total testosterone is not the only number that matters
If you only look at total testosterone, you can miss what is actually happening. The relevant additional markers include:
Free testosterone
Most of the testosterone in your blood is bound to proteins (mostly SHBG and albumin). Only a small percentage is "free" and biologically available to your cells. Free testosterone is the portion that actually does the work.
Two men can have the same total testosterone (say, 15 nmol/L) but very different free testosterone levels because their SHBG is different. The one with high SHBG has less free, active testosterone and may feel symptomatic. The one with low SHBG has more free, active testosterone and feels fine.
A complete picture requires both total and free testosterone, plus SHBG.
SHBG (Sex Hormone Binding Globulin)
SHBG binds testosterone, making it unavailable to your cells. High SHBG means less free testosterone even when total looks fine. Low SHBG means more free testosterone, but can be a sign of metabolic issues like insulin resistance.
SHBG normal range is typically 18-54 nmol/L. Outside that range significantly affects how total testosterone should be interpreted.
Oestradiol (oestrogen)
Men produce small amounts of oestrogen, mostly through conversion of testosterone via aromatase. Too much can cause symptoms (fatigue, low libido, mood changes, water retention) even with normal testosterone. Too little can also cause problems (bone density, mood, libido).
A typical adult male oestradiol range is around 40-160 pmol/L. Significantly outside this range warrants investigation.
LH and FSH
These are pituitary signals that tell the testes what to do. They help distinguish two different patterns of low testosterone:
- Primary hypogonadism: low testosterone, high LH/FSH. The pituitary is shouting at the testes to make testosterone but they cannot produce. The problem is at the testicular level.
- Secondary hypogonadism: low testosterone, low or normal LH/FSH. The pituitary is not signalling properly. The problem is higher up.
The distinction matters because it can guide treatment decisions.
How to interpret your own results
When you get your testosterone results back, a useful framework:
- Total testosterone above 15 nmol/L: probably fine. If you have no symptoms, you are unlikely to benefit from intervention. If you have significant symptoms, look at the other markers (free T, SHBG, oestrogen, thyroid).
- Total testosterone 10-15 nmol/L: the grey zone. Symptoms and full hormonal picture matter most here. Some men in this range feel fine. Others feel awful. Free testosterone and SHBG are essential to interpret.
- Total testosterone below 10 nmol/L: low. If symptoms are present, personalised TRT is often appropriate. If no symptoms, recheck with a second test (testosterone fluctuates) and investigate causes.
- Total testosterone below 8 nmol/L: clinically low by most guidelines. Treatment usually appropriate if symptoms are present.
The number alone does not tell the story. A 14 nmol/L reading might be problematic if your free testosterone is 0.2 nmol/L due to high SHBG. A 9 nmol/L reading might be acceptable if you feel completely fine, are not gaining weight, and your other markers are healthy.
When to test
A reasonable rule of thumb: if you have a cluster of symptoms that suggest low testosterone (persistent fatigue, low mood, brain fog, weight gain, reduced libido, weak erections, difficulty building muscle, poor sleep) and they have crept in over months or years, a comprehensive blood test is worthwhile.
Timing matters, but less rigidly than you might think. Testosterone is highest in the morning, so testing earlier in the day gives the most comparable result: we suggest before 12pm if you're under 40 and before 2pm if you're 40 or over. You don't need to fast, and a low result later in the day still counts.
A single low result should usually be confirmed with a second test, as testosterone can fluctuate based on sleep, stress, illness, and time of day. If both tests show low levels alongside symptoms, intervention starts to make sense.
What good clinical care looks like
The honest version: many men get a single testosterone reading at their GP, are told it is "normal" without anyone looking at the other markers, and walk away still feeling rubbish. This is not always a failure of the GP; it reflects how the NHS testosterone pathway is set up. The investigation is often narrow and reference-range based rather than clinical.
A more thorough approach, which is what Arc TRT offers, looks at:
- A comprehensive panel of relevant hormones and supporting markers
- Interpretation by a doctor who specialises in male hormonal health
- Symptoms and clinical history in the context of the bloods
- Repeat testing where needed to confirm patterns
- A plan that fits your situation, whether that involves lifestyle changes, treatment of a specific issue, or personalised TRT if appropriate
The numbers matter, but they only mean something when read alongside how you actually feel. That clinical context is what separates a useful investigation from a confused one.
The bottom line
"Normal" testosterone is a wider range than most people realise, and being in the lower part of normal does not mean you should feel normal. If you have symptoms that suggest low testosterone, the most useful step is a proper investigation with the right markers and the right clinical interpretation.
The numbers give you information. What you do with that information depends on how you feel, what your goals are, and what a clinician advises after looking at the full picture.
Sources: Travison TG et al., Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies, Journal of Clinical Endocrinology and Metabolism 2017; 102(4): 1161-1173, Table 4 (nmol/L converted from ng/dL at 1 nmol/L = 28.84 ng/dL). Hackett G et al., The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice, World Journal of Men's Health 2023; 41(3): 508-537.
Want to know where your levels sit?
Arc TRT offers home finger-prick testing and enhanced clinical panels, with results reviewed by a UK doctor. Over 3,000 men tested and counting.
This article is for general information and does not replace personalised medical advice. Speak to a qualified clinician about your individual circumstances.
Keep reading
For the complete picture, see our full guide to TRT in the UK, covering eligibility, blood test thresholds, NHS and private routes, costs and monitoring. If you are still working out whether any of this applies to you, start with the symptoms of low testosterone.
