Medical summary
There is no single authoritative UK testosterone-levels-by-age chart that can diagnose testosterone deficiency. A result must be interpreted using the reporting laboratory’s reference interval, the assay used, the time and conditions of sampling, symptoms, sex hormone-binding globulin (SHBG), relevant health conditions and repeat testing.
MYTRT treatment eligibility
MYTRT treats men only when they have compatible symptoms and meet both biochemical limits: total testosterone of 15 nmol/L or below, and free testosterone of 0.35 nmol/L or below.
For healthy, non-obese European and American men aged 19–39, a large assay-harmonisation study reported a total testosterone reference range of 264–916 ng/dL, approximately 9.2–31.8 nmol/L. That range was produced for a defined young population and calibrated assays; it is not a decade-by-decade UK treatment table and should not be applied unchanged to every man.[1]
Ageing is associated with a modest average fall, but individual change varies substantially. In the longitudinal European Male Ageing Study (EMAS), 2,395 men aged 40–79 with paired results had a mean annualised total testosterone change of −0.1 nmol/L and a mean free-testosterone change of −3.83 pmol/L. Weight change was an important influence.[2] Current EAU guidance summarises the age association as approximately 0.4% per year for total testosterone and 1.3% per year for free testosterone, while stressing that obesity, illness and other modifiable factors account for much of the variation.[3]
A testosterone number does not make the diagnosis by itself. Current EAU guidance requires compatible symptoms plus low morning total testosterone on two or more occasions, measured using a reliable assay in fasting conditions. It uses 12 nmol/L as a practical total-testosterone threshold for late-onset hypogonadism, not as a universal definition of health or an automatic reason to prescribe.[3]
Why a simple age chart can mislead
A chart that gives a “normal” total and free testosterone band for every decade can appear precise while hiding major uncertainty. Published ranges differ because studies recruit different populations and laboratories use different methods. Results are also affected by sleep, food intake, acute illness, medicines, body weight and SHBG.
The previous version of this article presented unsourced decade bands and described a single free-testosterone figure as an optimal threshold for every man. That framing has been removed. Professional recommendations discuss different calculated free-testosterone decision points in particular diagnostic contexts, but the result is method-dependent and no single figure is a universal target for health, performance or treatment.[4]
| Question | Evidence-based interpretation |
|---|---|
| Is there one normal UK level for each age? | No. Use the interval printed by the analysing laboratory and interpret it with the assay, sample conditions and clinical picture. |
| What is the best-harmonised reference interval? | In healthy, non-obese men aged 19–39, 9.2–31.8 nmol/L for total testosterone when assays are appropriately calibrated.[1] |
| Does testosterone always fall 1–2% each year? | No. EMAS found an average total-testosterone fall of about 0.1 nmol/L per year; EAU summarises an average 0.4% annual fall in total testosterone and 1.3% in free testosterone. Individual trajectories vary.[2][3] |
| Is one free-testosterone figure “optimal” for every man? | No. It is not a universal wellness or treatment target. Free testosterone must be interpreted using the calculation or method, SHBG and the wider assessment.[3][4] |
| Does one result diagnose deficiency? | No. Symptoms and properly collected repeat morning results are required; underlying causes must also be assessed.[3][4] |
What testosterone tends to do with age
Population averages are generally highest in early adulthood and lower in later life, but healthy ageing does not inevitably produce hypogonadism. EAU guidance notes that ageing accounts for only a small proportion of hypogonadism and that obesity, type 2 diabetes, chronic illness and overall poor health are major contributors.[3]
The longitudinal EMAS results also show why a fixed annual percentage should not be presented as an individual forecast. Average total testosterone changed by −0.1 nmol/L per year, but the standard deviation was 0.95 nmol/L per year. Some men therefore changed far more, some changed very little and some increased. Weight loss was associated with an increase in testosterone, while weight gain was associated with a decrease.[2]
This means a result at 55 cannot reliably be predicted from a result at 35. A clinician should look at what has changed in the person’s health, medicines, sleep, weight and symptoms rather than assume that age explains the number.
Reference intervals, diagnostic thresholds and treatment targets are different
These three concepts should not be used interchangeably.
A laboratory reference interval describes the distribution of results in a defined reference population using a particular method. It does not prove that every value inside the interval is healthy or that every value outside it represents disease.
A diagnostic threshold helps clinicians decide when a result, combined with symptoms and repeat testing, supports a diagnosis. EAU guidance uses 12 nmol/L as a practical total-testosterone threshold for late-onset hypogonadism and recommends repeat measurements before treatment.[3] BSSM guidance uses a more graduated framework: two morning total-testosterone results below 8 nmol/L or calculated free testosterone below 0.225 nmol/L usually support treatment when symptoms are present; results from 8–12 nmol/L require clinical judgement, while total testosterone above 12 nmol/L or calculated free testosterone above 0.225 nmol/L generally argue against treatment.[4]
A treatment target is used after a diagnosis and prescription to guide monitoring. It must not be presented as the normal untreated range for the general population. BSSM discusses a total-testosterone treatment target of 15–30 nmol/L for men receiving therapy.[4] That is an on-treatment target, not an age-chart reference interval and not evidence that an untreated man below 15 nmol/L automatically needs testosterone.
How to prepare for a meaningful testosterone test
EAU guidance advises measuring total testosterone in the morning, between 07:00 and 10:00, and in the fasting state. A low result should be confirmed with another properly collected sample before testosterone therapy is considered.[3]
Testing during acute illness can produce a misleadingly low result. Sleep pattern is also relevant, particularly for night-shift workers, because testosterone rhythm follows sleep as well as clock time. The clinician should know about medicines and substances that may alter the hypothalamic–pituitary–testicular axis or SHBG.
If total testosterone is low or borderline, the wider assessment may include SHBG, albumin, luteinising hormone, follicle-stimulating hormone and prolactin. Calculated free testosterone can be useful where SHBG is likely to distort the relationship between total and biologically available hormone. Direct free-testosterone immunoassays are not considered sufficiently accurate; equilibrium dialysis or a validated calculation is preferred.[3]
How clinicians interpret a result
The first question is whether the sample is reliable. A clinician will check the collection time, fasting status, recent illness, sleep and the laboratory method. If the result is low, it is normally repeated under appropriate conditions.
The second question is whether there are compatible symptoms and signs. Reduced sexual desire, erectile dysfunction and fewer spontaneous or morning erections are more specific than tiredness or low mood, which can have many causes.[3][4]
The third question is why the result is low. Obesity, type 2 diabetes, medicines, pituitary disease, testicular disease, sleep apnoea, acute illness and previous anabolic-steroid use can all change the assessment. Luteinising hormone and follicle-stimulating hormone help distinguish testicular from hypothalamic or pituitary causes.
The final question is whether treatment is appropriate and safe. Fertility plans matter because external testosterone can suppress sperm production. Haematocrit, prostate history, cardiovascular history and other safety factors must be reviewed before prescribing.
What your result does and does not tell you
A result within the laboratory interval does not explain every symptom, and a result below the interval does not prove that testosterone is the cause. Symptoms such as fatigue, reduced concentration and low mood can also reflect poor sleep, anaemia, thyroid disease, depression, medicine effects, metabolic illness or other conditions.
Likewise, being lower than an average for younger men is not the same as having a diagnosable deficiency. Comparing yourself with an online “optimal” figure can lead to unnecessary concern. The safest next step is a clinician-led assessment based on repeat results and the full health picture.
If you want to understand how MYTRT assesses testing and suitability, read our TRT eligibility criteria. For a broader explanation of symptoms and differential diagnoses, see low testosterone symptoms.
Frequently asked questions
What is a normal testosterone level for my age?
There is no single UK number for each age. Use the reporting laboratory’s interval and have the result interpreted alongside sample timing, assay method, symptoms, SHBG and health conditions. The harmonised 9.2–31.8 nmol/L interval applies specifically to healthy, non-obese men aged 19–39 and appropriately calibrated assays.[1]
Is testosterone expected to fall by 1–2% every year?
Not for every man. Current EAU guidance summarises average falls of about 0.4% per year in total testosterone and 1.3% per year in free testosterone, while longitudinal EMAS data found a mean absolute total-testosterone change of −0.1 nmol/L per year. Weight, health and lifestyle substantially affect the trajectory.[2][3]
Is there one optimal free testosterone level?
No. It is not a universal optimal threshold. Free testosterone is method-dependent and should be interpreted with total testosterone, SHBG, symptoms and sample quality. Professional guidance uses different decision points, which is one reason a single online number should not drive diagnosis or treatment.[3][4]
Can I have symptoms even if my testosterone is in range?
Yes, but the symptoms may have another cause. A clinician should assess sleep, mental health, thyroid function, anaemia, medicines and metabolic health rather than assuming that testosterone is responsible.
How many tests are needed before a diagnosis?
Current EAU guidance recommends compatible symptoms plus low morning total testosterone on two or more occasions, measured in fasting conditions using a reliable assay.[3]
Is an on-treatment target the same as a normal untreated range?
No. A treatment target is used to monitor a person who has already been diagnosed and prescribed therapy. It must not be used as a population reference interval or as proof that an untreated person needs TRT.
References
[1] Travison TG, Vesper HW, Orwoll E, et al. Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161–1173. View source
[2] Camacho EM, Huhtaniemi IT, O’Neill TW, et al. Longitudinal results from the European Male Ageing Study. Eur J Endocrinol. 2013;168(3):445–455. View source
[3] European Association of Urology. Male Hypogonadism. EAU Guidelines on Sexual and Reproductive Health. 2026. View source
[4] Hackett G, Kirby M, Rees RW, et al. British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency. World J Mens Health. 2023;41(3):508–537. View source
