Testosterone Levels in Men: Normal, Low and High

Testosterone is the main male sex hormone. It supports sex drive and erections, muscle and bone strength, energy, mood, and the production of sperm and red blood cells. Levels are highest in the early morning and decline slowly from around the age of 30 to 40, which on its own is unlikely to cause problems.

This guide explains what low, borderline, normal and high testosterone results mean for men, why the time of day of your blood test matters, how free testosterone and SHBG change the picture, and when to speak to your GP.

Test it in Chiswick: our Testosterone blood test costs £49, with your result explained in person by a practitioner. No GP referral needed. Book this test or call 020 4515 0000. Prefer to test at home? A home finger-prick kit is also available, ask us when you enquire.

Quick answer

For adult men, UK guidance from the British Society for Sexual Medicine (BSSM) and NHS laboratories treats a morning total testosterone below 8 nmol/L as low, 8 to 12 nmol/L as borderline, and above 12 nmol/L as not low. In the borderline zone, free testosterone and SHBG help decide. A single low result is never enough: the test should be repeated on a second morning, ideally about four weeks later. Upper limits are often around 25 to 30 nmol/L, but ranges vary between laboratories, so always read the range on your report.

What testosterone does

Most testosterone is made in the testes, under the control of two pituitary hormones: luteinising hormone (LH) and follicle stimulating hormone (FSH). If the testes are not working well, LH and FSH usually rise. If the pituitary is not sending the signal, LH and FSH are low or normal. This is why a low testosterone result is often followed by LH and FSH tests.

In the blood, most testosterone is tightly bound to sex hormone binding globulin (SHBG). The rest is loosely bound to albumin or free, and these are the portions your body can use.

What your testosterone result means

• Low (below 8 nmol/L): testosterone deficiency is likely if the result is confirmed on a repeat morning sample and you have symptoms. BSSM notes that men with levels in this range tend to see the best improvement in sexual symptoms with treatment.
• Borderline (8 to 12 nmol/L): this is a grey zone. BSSM advises checking free testosterone, worked out from your total testosterone, SHBG and albumin, before drawing conclusions.
• Within range (above 12 nmol/L): BSSM guidance is that men above this level do not need testosterone treatment, as long as free testosterone is also not low.
• High (above the laboratory upper limit): usually linked to testosterone treatment or anabolic steroid use, or a sample taken soon after applying testosterone gel.

Reference ranges differ between laboratories and can be adjusted for age. One NHS laboratory, for example, quotes 8.3 to 30.2 nmol/L for men aged 18 to 49 and 7.7 to 24.8 nmol/L for men over 50. Always compare your result with the range printed on your own report.

Free testosterone and SHBG

Total testosterone can be misleading when SHBG is unusually high or low. SHBG tends to be higher in older men and with an overactive thyroid or some liver conditions, which can leave less testosterone free even when the total looks acceptable. SHBG tends to be lower with excess weight and type 2 diabetes, which can make the total look low when the free level is adequate.

BSSM recommends a calculated free testosterone, based on total testosterone, SHBG and albumin, rather than direct free testosterone immunoassays. A calculated free testosterone below 225 pmol/L (0.225 nmol/L) provides supportive evidence of deficiency. BSSM also advises checking SHBG when total testosterone is borderline, particularly in older men and men carrying extra weight.

Our Testosterone Check (£59) measures total testosterone, SHBG, albumin, calculated free testosterone and the free androgen index in one sample. The Testosterone Check Plus (£79) adds LH, FSH and oestradiol, which helps show where a low result is coming from.

Symptoms of low testosterone

Symptoms build gradually and overlap with other conditions. The more of these you have, the more likely a genuine deficiency is:

• Low sex drive, fewer morning or night-time erections, or erectile dysfunction
• Tiredness and low energy
• Low mood, irritability or poor concentration
• Loss of muscle and strength
• More body fat, including breast tissue (gynaecomastia)

The NHS points out that stress, depression, anxiety, relationship or work pressures, poor sleep, heavy drinking and inactivity can cause very similar symptoms even when testosterone is normal.

Common reasons for low testosterone

• Excess weight and type 2 diabetes: the NHS notes that late-onset hypogonadism is more likely in men who are obese or have type 2 diabetes.
• Short-term illness: levels often drop temporarily during an acute illness, so testing is best delayed until you have recovered.
• Medicines: some medicines, including opioid painkillers and steroids, can lower testosterone.
• Pituitary causes: including a raised prolactin level, which BSSM advises checking when LH and FSH are both low.
• Testicular causes: such as past injury, infection, treatment for cancer, or genetic conditions such as Klinefelter syndrome.

What a high result can mean

A testosterone level above the reference range in a man who is not on treatment is uncommon. The most frequent reasons are testosterone replacement therapy, a sample taken within a few hours of applying testosterone gel, or anabolic steroid use. The NHS warns that anabolic steroids can cause shrunken testicles, a reduced sperm count, infertility and breast development, along with raised blood pressure and cholesterol.

If you are on testosterone therapy, your prescriber will also monitor your full blood count, because testosterone can raise haematocrit and thicken the blood. Our Men’s Hormone and TRT Panel (£199) covers testosterone, full blood count, PSA, liver function and cholesterol, which are commonly checked during treatment.

What to do with your result

• Repeat a low or borderline result: BSSM recommends at least two morning measurements, preferably about four weeks apart and not during an acute illness.
• Check LH and FSH: BSSM advises measuring these when total testosterone is below 12 nmol/L, to show whether the cause is in the testes or the pituitary.
• Look at the bigger picture: weight, blood sugar, sleep, alcohol and medicines all affect testosterone. Our practitioner will talk these through with you.
• Treatment decisions: testosterone replacement is offered only when deficiency is confirmed on repeat testing and you have symptoms. The NHS notes a GP may refer you to an endocrinologist.

When to see your GP

Book a GP appointment if you have:

• A confirmed low testosterone result and ongoing symptoms
• Erectile problems that do not settle, as they can be linked to other health conditions
• Swelling or a lump in the breast or a testicle
• A very low testosterone result together with headaches or changes in your vision

Get urgent help: call 999 or go to A&E if you have chest pain, sudden weakness or numbness on one side, or difficulty speaking. If you are unsure how urgent your symptoms are, call NHS 111.

Who should consider a testosterone test

• Men with low sex drive, erectile problems or fewer morning erections
• Men with persistent tiredness, low mood or loss of muscle without a clear reason
• Men with type 2 diabetes or significant excess weight who have symptoms
• Men on testosterone therapy who need monitoring

NHS guidance advises against testing men who have no symptoms or only vague ones, because a result without symptoms rarely changes what should happen next.

Preparing for your test

• Book a morning appointment: BSSM recommends a sample between 7am and 11am. This is especially important for men under 40, whose levels fall more through the day.
• Fasting: BSSM suggests fasting where practical, because eating can lower the result. Water is fine.
• Timing around illness: wait until you have recovered from any recent infection or illness.
• Medicines and supplements: tell us about all medicines. If you take high-dose biotin, NHS laboratories advise leaving at least 8 hours between your last dose and the sample.
• On testosterone treatment: tell us what you use and when you last applied or injected it, so the result can be read correctly.

How often to retest

Confirm a low or borderline result with a second morning test about four weeks later. If a borderline result comes with ongoing symptoms, recheck after a few months. Men on testosterone therapy are usually monitored more often in the first year, then at least once a year once stable, as agreed with their prescriber.

Frequently asked questions

Is a testosterone level of 10 nmol/L low?

A result of 10 nmol/L sits in the borderline range of 8 to 12 nmol/L. It is not low enough on its own to confirm deficiency. The next steps are a repeat morning sample and a free testosterone calculation using SHBG and albumin, alongside a review of your symptoms.

Is 15 nmol/L a normal testosterone level for a man?

Yes. A morning level of 15 nmol/L is above 12 nmol/L, which UK guidance does not treat as low. If you still have symptoms, free testosterone, thyroid function, iron and vitamin levels and your general health are worth reviewing.

Can I have a testosterone test in the afternoon?

It is better not to. Testosterone falls through the day, so an afternoon result can look low when your morning level is normal. Book between 7am and 11am for a result that can be compared with the guidance.

Is free testosterone more important than total testosterone?

Total testosterone is the starting point. Free testosterone becomes important when total testosterone is borderline or when SHBG is unusually high or low, for example in older men or men carrying extra weight.

Testosterone testing in Chiswick

You can have your blood taken at Omnia Lifestyle, 8 to 9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ. We are a short walk from Turnham Green station on the District line (Piccadilly line trains stop there early in the morning and late in the evening only), and buses 94, E3 and 272 stop nearby. Limited parking is available on request when you book. Your sample is analysed at the Randox accredited laboratory, you do not need a GP referral, and a practitioner explains your result with you in person. Most results are ready within a few working days, and a GP feedback report is available on request.

Start with our Testosterone test, or choose the Testosterone Check if you want free testosterone and SHBG included. See our men’s health blood tests for wider panels, or compare every blood test and price. You may also find our guides to blood tests for low libido and SHBG levels helpful.

This article is general information, not medical advice. Discuss your results with your GP or practitioner.