As you can see in the graph above, the average testosterone level in the population is dropping every decade.

You would expect that as a result, more and more men would be suffering from low testosterone. In fact, the rates of men being treated for this condition has increased but not in line with the drop we see in overall levels.

Whilst there are many reasons for this reduction in male hormone levels, from obesity to environmental chemical exposure, it remains difficult for the medical community to become comfortable with diagnosing and treating this issue.

There are complex reasons behind this. These range from poor knowledge and understanding of the condition, to stigma around testosterone itself, to the use of inaccurate normal male testosterone levels.

Here we will look at the history behind these values and how they are measured. We will look at why they are not a good indicator of low testosterone when used alone or relied on entirely without taking symptoms into account. We will consider the importance of looking at more than just one value and how different factors can affect the amount of testosterone available for use by the body.

What is testosterone? 

Testosterone is a hormone or chemical messenger produced mainly by the testes in men and in smaller amounts in women. It is considered a sex hormone due to its effects on the sex organs and production of male characteristics and behaviours. It has effects throughout the body, affecting the body, the mind, behaviour, fertility and development. It is extremely important for male well-being and physical health, which makes it even more surprising that some parts of the medical community are so against treating it effectively.

Testosterone in men

How is it measured?

Testosterone is usually measured through a capillary blood test at home (you can find these here) or taken by a doctor, phlebotomist or nurse from a vein. The test is taken at around 9am due to the release time of testosterone in the body (known as the circadian rhythm). This is the time when testosterone blood levels are at their highest.

This serum blood test is then analysed in a laboratory and different hormones reported on. These come back on a form with the ‘normal’ male testosterone levels attached (see below).

These are my test results from before starting TRT.

Male testosterone levels before TRT

As you can see I had ‘normal’ total and low free testosterone levels. This is despite having several symptoms of low testosterone pretty much the whole time. If I’d visited a UK NHS GP I would have undoubtedly been told that I was just depressed and anxious. I had insomnia, couldn’t think straight, had trouble with simple arithmetic, was losing the muscle and strength I had trained the past 10 years for, I was grumpy and lethargic and I had anxiety the whole time – my life was a mess.

You may be asking, ‘what do these values all mean?’.

The important ones to understand now are the ‘total testosterone’ and ‘free testosterone’ levels. Total testosterone can be an indicator of low levels of testosterone. However, the Endocrine Society (amongst others) have rightly indicated that many men have ‘normal’ total testosterone levels but very low ‘free’ and/or ‘bioavailable’ testosterone levels. If this is the case then a man may have all of the symptoms of low testosterone but show as normal on a testosterone test.

Guess which values are tested for by most doctors? You’re right: they only usually test for total testosterone. And if this is ‘within normal male testosterone levels’ the patient will be told that it is all fine and that something else is to blame for their symptoms (normally depression).

What are normal male testosterone levels?

Normal values are the range of levels of testosterone found in studies of male populations. In the case of most values produced these are from an age range of 20-80 year old men! They also include men with illnesses and in varying degrees of stress/environmental factors. The researchers then take all of the results from this group of men from different age groups and states of health and put it in a graph. Then, the top 5% and bottom 5% are removed and you are left with the ‘normal’ male testosterone levels/values.

Testosterone Levels

Can you see the problem with this?

If we know that the average man’s testosterone levels drop over time from the age of 30, then it is clear that comparing a 20 year olds’ levels with the testosterone levels of an 80 year old is rather silly!

Unfortunately, this is what happens in GP surgeries across the country. Men are being denied treatment and laughed out of GP surgeries despite suffering from very real and debilitating symptoms. One of my friends was told that he couldn’t possibly have low testosterone because he could grow a beard (he was found to have low testosterone and is now on TRT). Another was told that he was ‘too muscley’ to have low testosterone.

Examples of these ridiculous statements are popping up way too frequently to not be taken seriously! Many men who have low testosterone are being treated with anti-depression medication (SSRIs) instead of treating the real conditions behind their mental health issues. These medications often reduce testosterone production even further, exacerbating the condition (studies in animals only so far).

Another issue with these ‘normal’ testosterone levels are that the endocrine societies responsible for producing the values can’t seem to decide on what constitutes a low level that needs treatment. They vary considerably and can result in a man not receiving the treatment they require and would benefit from if they were tested elsewhere.

How do these normal testosterone levels compare?

There are many endocrine societies throughout not only the world but also several throughout Europe, North America and Asia. They can not be expected to all agree on what values should be used but some of the discrepancies across the board are quite considerable.

Why are these values not a good indicator of low testosterone?

Doctors are assessing 20 year olds’ testosterone levels based on the average levels of all men including 80 year old men with comorbidities (illnesses). The decision that someone has low testosterone is based on them being in the lowest 5% of these men. It is not at all related to the symptoms of those men. The ‘normal’ levels only look at the highest to lowest levels of all men in a population, they haven’t correlated this with whether the men in that population are experiencing low testosterone symptoms! If doctors look purely at these reference ranges then they ignore the fact that some men will experience low testosterone symptoms at higher levels of testosterone than other men. (The graph below demonstrates how the reference ranges are calculated but it has completely different ‘average’ testosterone levels to what we see in other studies).

Testosterone Levels by Age

‘Total testosterone levels are affected by alterations in SHBG that occur in obesity, old age, diabetes mellitus, hyper- and hypothyroidism, and acromegaly, and in men taking certain medications. Accurate and reliable assays for free or bioavailable testosterone measurements usually are not available in local laboratories, and these tests should be performed in a reliable reference laboratory. Free testosterone measurements by analog methods are frequently available in local laboratories, but these measurements are affected by alterations in SHBG and are inaccurate. Their use is not recommended.’ 

Testosterone level in men with type 2 diabetes mellitus and related metabolic effects: A review of current evidence. Cheung et al., (2015) Journal of Diabetes Investig. 6(2): 112–123.

As you can see even The Endocrine Society discourages doctors from relying on just total testosterone levels, yet because the test for free testosterone isn’t as cheap or easy to attain it is often neglected by GPs. Read more from the Endocrine Society guidelines here.

Free and bioavailable testosterone

Only 0.5–3% of circulating testosterone is unbound or “free. ” The term “bioavailable testosterone” refers to unbound testosterone plus testosterone bound loosely to another hormone: albumin. This term is because it is thought that in addition to the unbound testosterone, albumin-bound testosterone is bioavailable because it can separate from albumin to be used in the body.

‘Free or bioavailable testosterone concentrations should be measured when total testosterone concentrations are close to the lower limit of the normal range and when altered SHBG levels are suspected, e.g. in older men and in men with obesity, diabetes mellitus, chronic illness, or thyroid disease’.

So it is easy to see why just measuring total testosterone is not sufficient to diagnose testosterone deficiency!

What are normal male testosterone levels by age?

Age Range Average total testosterone (nmol/l) Average free testosterone (nmol/l) SHBG
25-34 21.38 0.428 35.5
35-44 23.14 0.356 40.1
45-54 21.02 0.314 44.6
55-64 19.49 0.2888 45.5
65-74 18.15 0.239 48.7
75-84 16.32 0.207 51.0
85-100 13.05 0.186 65.9

These results have been available since 1996 yet they continue to be ignored in favour of more generalised values.

These results do show a reduction in testosterone levels with age, as well as an increase in SHBG and a further reduction in average free testosterone levels with age. This graph may indicate why some men experience symptoms of low testosterone at levels lower than those often treated. It also demonstrates why SHBG and free testosterone are so important for testing. You can see the updated 2005 study by Vermuelen and Kaufman here.

Average testosterone levels by age
It would be easy and more accurate for doctors to use these levels to produce averages per age group. They are based on age and could be combined with symptoms to diagnose testosterone deficiency more effectively.
SHBG levels chart

You can see that SHBG (sex hormone binding globulin), which attaches to testosterone and makes it unable to bind to receptors in the body, rises with age. This is one reason why a man’s free testosterone drops so much with age. And it’s another good reason to always have free testosterone checked when worried about low testosterone symptoms!

DHEA is another testosterone precursor (testosterone is produced from it) that drops massively with age. It is responsible for many male traits and physical changes in the body. It has been shown to increase strength and reduce body fat levels in men. Many men take it as an anti-ageing supplement. With lower testosterone levels this precious hormone also reduces significantly.

Treat the patient not the lab results!

So what is the take home message for all of this? Treat the patient, NOT the blood results. A man who had very high testosterone levels when a younger man may have very real and devastating symptoms but be within the lower ranges of the ‘normal values’. He will be laughed out of the average GP’s office when his blood results come back within range.

Similarly, a young man of 25 years old may feel extremely fatigued and depressed at a testosterone level similar to that of a low-testosterone 80 year old. But based on the ‘normal male testosterone values’ be considered normal! He will be struggling with all of the symptoms of low testosterone and will probably be put on SSRIs to attempt to treat his depression and anxiety. This is why we at OptiMale believe in assessing both normal blood values and a patient’s symptoms. If you come to us with low-normal testosterone levels our doctors can often offer a trial of testosterone replacement therapy to assess whether this is the cause of your symptoms.

Symptoms of low testosterone

These are the symptoms most commonly seen in men with low testosterone, if you notice you’ve developed some of these then the next step is to get your blood tested for low total and free testosterone levels.

More specific signs and symptoms (these symptoms are closely linked to lower than normal male testosterone levels):

  • Incomplete or delayed sexual development, eunuchoidism
  • Reduced sexual desire (libido) and activity
  • Decreased spontaneous erections
  • Breast discomfort, gynaecomastia
  • Loss of body hair axillary (armpit) and pubic hair, reduced shaving frequency
  • Small of shrinking testes
  • Low or zero sperm count
  • Height loss, low trauma fractures reduced bone mineral density
  • Hot flushes, sweats
Signs of Low Testosterone

Less specific signs and symptoms (these may indicate low testosterone levels or a different condition):

  • Decreased energy, motivation, initiative and self-confidence
  • Brain fog
  • Feeling depressed or anxious, depressed mood, dysthymia
  • Poor concentration and memory
  • Sleep disturbance, increased sleepiness
  • Mild anaemia
  • Reduced muscle bulk and strength
  • Increased body fat percentage
  • Reduced work and physical performance

Get treated!

If you are noticing several of these symptoms then it is definitely worth getting your testosterone blood results tested. It is a simple, quick test that you can do at home. We will send it directly through the post and we test for everything including total testosterone, free testosterone, SHBG and estrogen levels at an extremely competitive price (our test is £59.99 compared to £79+ elsewhere).

Benefits of normal/high testosterone

  • Mental acuity / no brain fog
  • Muscle strength and size increased
  • Improved lipid values
  • Reduced CV risk
  • Improved bone density
  • More assertive
  • Better concentration and drive
  • Less anxiety
  • Improved joie de vivre / outlook on life
  • No IBS
  • Deeper more stable voice

I have noticed 8 out of 11 of these since starting testosterone replacement therapy (the others need specific tests before and after to identify). I have even had blood tests that show perfect lipid values and PSA (prostate specific antigen) levels.


Testosterone replacement therapy is not for everyone. However, if you are starting to notice some of the symptoms above then it is really important that you get tested.

In the modern world where normal male testosterone levels are dropping year by year, your health and happiness depends on having good levels.

It is not the demon hormone that it is made out to be in the media – it improves male mental and physical health when at optimal levels. It improves your relationships and social life. It doesn’t turn you in to a horrible person. If anything it is likely to make you more successful and happy.

Buy a blood test now and find out for certain whether low testosterone is affecting your life.

Or contact us using the form below and we would be happy to answer any questions you might have!

Dr Chris Airey

Dr Chris Airey

Medical Director

This article has been medically reviewed for accuracy by Dr Airey on 12th September 2020.

Dr Chris Airey is a fully registered UK doctor with the GMC (General Medical Council) Reference No: 7490533.
He trained at the University Hospital Southampton and graduated as a Doctor with a joint Bachelor of Medicine and a Bachelor of Surgery, plus a Masters in Medical Science, completing his research project in the Medical Neurosciences Department.
He is undertaking a Master of Science course in Endocrinology and is a member of the European Society for Sexual Medicine, and the Androgen Society.
He has personal experience with taking Testosterone Replacement Therapy and is a pioneer in UK treatment protocols for Testosterone Deficiency Syndrome.

Please feel welcome to contact us with any questions with the form below