Results and reference ranges

Normal Testosterone Levels in Men: UK Results Explained

A detailed UK guide to testosterone levels in nmol/L, borderline results, laboratory ranges, SHBG, calculated free testosterone and the next step after an abnormal result.

By Mens Health TRTUpdated 17 July 202611 min read

The short answer

UK testosterone results are usually reported as total testosterone in nmol/L. There is no single number that diagnoses testosterone deficiency by itself. The 2026 European Association of Urology guideline uses 12 nmol/L or below as a diagnostic threshold in men who also have compatible symptoms, with treatment effects generally more apparent at lower levels. A low or borderline result should be repeated in a morning fasting sample and interpreted with the laboratory range, symptoms, SHBG, calculated free testosterone and other hormone tests where indicated.

Key points

A laboratory reference range is not the same as a treatment threshold.
Diagnosis requires symptoms plus consistently low, appropriately timed testosterone results.
Results between about 8 and 12 nmol/L often need closer interpretation rather than a yes-or-no answer.
SHBG can make total testosterone look more or less reassuring than the biologically available amount.
Age, weight, illness, sleep, medicines and sampling conditions can influence a result.

Man and clinician reviewing a testosterone blood test result together — A testosterone number becomes meaningful only when timing, symptoms and the wider hormone picture are considered.

How are testosterone levels reported in the UK?

Most UK laboratories report total testosterone in nanomoles per litre, written as nmol/L. Total testosterone includes testosterone bound tightly to sex hormone-binding globulin (SHBG), testosterone bound more loosely to albumin and the small fraction circulating freely. The headline number is useful, but it does not describe each fraction separately.[2,1]

Some websites use nanograms per decilitre, or ng/dL, because that unit is common in the United States. A laboratory or clinician can convert units, but self-conversion should not be used to compare results taken under different conditions or analysed by different methods. The original report, sampling time and laboratory reference interval should stay together.

What testosterone level is considered low?

Current European guidance recommends 12 nmol/L as a useful threshold for diagnosing symptomatic male hypogonadism, while also recognising that the likely benefit from treatment is greater in men with more clearly reduced levels. This is a clinical threshold, not a claim that every result below 12 requires TRT or that every result above 12 explains away symptoms.[1]

UK guidance also treats the middle range with care. Results around 8 to 12 nmol/L may be described as borderline and often prompt a repeat sample, review of SHBG and calculated free testosterone, and investigation of the symptom pattern. A clinician should use the method and reference interval supplied by the testing laboratory rather than applying an internet cut-off in isolation.[3,2]

A practical way to understand result patterns, not a self-diagnosis tool
Result pattern	What it may mean	Usual next step
Below about 8 nmol/L	More clearly reduced, particularly when compatible symptoms are present	Repeat under correct conditions and investigate the cause
About 8 to 12 nmol/L	Borderline range where SHBG and clinical context can change interpretation	Repeat, review symptoms and consider calculated free testosterone
Above about 12 nmol/L	Testosterone deficiency becomes less likely as the explanation	Review the laboratory range and investigate other causes of symptoms

Why do testosterone reference ranges differ between laboratories?

Laboratories may use different analysers, calibration methods and reference populations. This can produce slightly different lower and upper limits even when the sample belongs to the same person. The range printed beside your result is therefore important, but it still needs clinical interpretation.[2]

A reference interval describes where results fall in a selected population; it does not automatically define who has a symptomatic hormone disorder or who benefits from treatment. That distinction is one reason reputable services require both a symptom history and biochemical confirmation before discussing a prescription.

What do SHBG and calculated free testosterone add?

SHBG is a protein that binds testosterone in the bloodstream. When SHBG is unusually high, total testosterone can look adequate while calculated free testosterone is lower. When SHBG is low, total testosterone can appear reduced even though the available fraction is less concerning. Obesity, thyroid conditions, liver health, medicines and other factors can affect SHBG.[1,4]

Calculated free testosterone is derived from total testosterone, SHBG and usually albumin. It can be helpful when the total result is borderline or when a condition that changes SHBG is present. It should not be treated as a more impressive number to optimise; its value is in resolving a specific interpretation problem.[2,1]

What can temporarily lower a testosterone result?

Testosterone follows a daily rhythm and is generally assessed in a fasting morning sample. Eating before the test, taking it later in the day, acute illness, severe sleep disruption, night-shift work and major calorie restriction can all make a result harder to interpret. A falsely reassuring result is also possible if timing does not match the clinical question or a treatment formulation.[4,2]

Longer-term influences include obesity, type 2 diabetes, chronic illness, heavy alcohol use and medicines such as opioids or corticosteroids. These factors do not mean symptoms should be dismissed. They mean the clinician should look for reversible or important underlying causes before labelling the result as age-related low testosterone.[4,5]

Record the time of the sample and whether you had fasted
Avoid testing during an acute illness unless a clinician advises otherwise
Tell the clinician about shift work, sleep loss and recent major weight change
List prescription medicines, hormones, anabolic steroids and supplements honestly
Use a repeat morning result rather than relying on one isolated number

What should you do after a low or borderline result?

Do not start testosterone or change a prescribed treatment from one result. Arrange a clinical review and, when appropriate, a repeat morning fasting test. LH, FSH, prolactin, SHBG and calculated free testosterone may help identify whether the issue relates to the testes, pituitary signalling, binding proteins or a temporary functional suppression.[1,2]

Seek prompt medical advice when a very low result occurs with severe headache, visual change, breast discharge, a testicular lump or other concerning symptoms. For most men, the next step is less dramatic: confirm the result properly, connect it to symptoms and decide what further investigation is justified before discussing treatment.

Questions people ask

Common questions, answered clearly.

Is 10 nmol/L testosterone low for a man?

A result of 10 nmol/L sits in a range that many guidelines treat as borderline. It may be clinically relevant when compatible symptoms are present, but it should usually be repeated in a morning fasting sample and interpreted with the laboratory range, SHBG, calculated free testosterone and other findings.

Is 12 nmol/L a normal testosterone result?

Twelve nmol/L is close to a commonly used clinical threshold, not a universal pass or fail point. Symptoms, repeat testing, laboratory method and SHBG can all affect the conclusion. A clinician should interpret the actual report rather than the number alone.

What is a normal testosterone level for a 40- or 50-year-old man?

There is no single age-specific target that diagnoses or excludes hypogonadism. Testosterone may decline with age, but health conditions and weight often have a stronger effect. Use the laboratory range and a clinical assessment rather than an online age chart.

Can testosterone be low one day and normal the next?

Yes. Levels vary with time of day, food intake, sleep, illness and normal day-to-day biology. That is why a low result is normally confirmed on a separate morning before diagnosis or treatment.

Can a normal testosterone result still need investigation?

Yes. Persistent symptoms may have another cause, and an apparently normal total testosterone result can occasionally need SHBG and calculated free testosterone context. The appropriate next step depends on the full clinical picture.

Sources and editorial standard

Mens Health TRT uses primary clinical guidance and NHS patient information. Sources were checked on 17 July 2026. Clinical guidance can change, so follow advice from the professional responsible for your care.