Benefits of testosterone replacement therapy

If you have only just heard about testosterone replacement therapy then you’d be forgiven for being a bit sceptical about its benefits.

At first glance the benefits look too good to be true, improved physique, better mood, better sex, more confident and better health…

Are these benefits real or are they overblown? How likely are you to really notice everything on this list and how long does it take for the benefits to be seen?

The answers aren’t straightforward and there are individual differences as well as complex reasons why TRT benefits some more than others.

What is testosterone replacement therapy?

Testosterone replacement therapy is the administration of the testosterone hormone into the body, to replace low levels of natural production.

It is called replacement because the natural production of the body reduces with the addition of exogenous testosterone (from outside the body) and is eventually replaced (this can be avoided by the use of HCG).

You can learn more about testosterone replacement therapy on our FAQ here.

Testosterone levels decline by around 1% per year after the age of 30. As well as this SHBG increases in the body with age, leading to lower free testosterone levels.

In some men this leads to low testosterone symptoms.

Other young men have conditions such as damage to the testicles from cancer or varicoceles, pituitary issues, genetic problems that lead to incomplete sexual development or have low testosterone for unknown reasons.

What are the benefits of testosterone replacement therapy (TRT)?

1. Improved mood – reduced anxiety

2. Improved libido (sex drive)

3. Improved assertiveness

4. Improved confidence

5. Better erection quality

6. Better sleep quality

7. Increased muscle mass and strength

8. Improved beard growth

9. Better vascularity and blood supply

10. Deeper and more stable voice

11. Improved bone density

12. Improved cognition including memory and mental acuity

13. Reduced all-cause mortality (deaths over a time period compared to men not on testosterone replacement therapy)


Improved mood and cognition

Jung and Shin (2016) demonstrated that the benefits of testosterone replacement therapy improved various aspects of mental health in men with testosterone deficiency.

They noted improvements in memory, mental acuity and mood.

In this study there were very few side effects, and none were serious. It is common for men who start treatment to notice a return to normal levels of brain function, where before they suffered from ‘brain fog’. Brain fog is when men struggle to perform simple mental arithmetic, remember things that happened recently, and find concentrating difficult.

Men may also find that their motivation and drive is reduced.

The effect of testosterone administration on cognitive function and depression in hypogonadal men is believed to be related to the enhancement of brain perfusion, which is supported by the fact that there are androgen receptors in the brain, suggesting that steroid hormones play a role in neuronal function.

Interestingly they go on to hypothesise the potential benefits this could have on men with other mental health conditions. In particular, they refer to a study on men with mild alzheimer’s.

The effects of TRT in men with mild cognitive impairment or Alzheimer’s disease have been evaluated in small placebo-controlled trials. For example, Cherrier et al [17] evaluated a sample of 32 subjects, which included 17 men with mild cognitive impairment and 15 with Alzheimer’s disease. At the 6-week follow-up, patients who received TRT showed significantly better scores regarding spatial memory, constructional abilities, and verbal memory compared to those noted in the placebo group. Taken together, these results suggest that TRT has a beneficial effect on cognitive function.

This is clearly a very interesting finding and something that needs further research. There is some evidence that low testosterone reduces perfusion (supply of blood to tissues) in various areas of the body – this can lead to certain conditions and improved testosterone levels often provide relief from conditions such as diabetes that have the side effect of reducing blood supply to regions.

Improved libido (sex drive)

Hackett et al. (2017)  found that men with type 2 diabetes and low testosterone saw large improvements in sexual desire and erection quality after starting testosterone replacement therapy. This is a common benefit we see in our patients within the first 6 months of TRT.

Improved erectile function

There are many treatments for erectile dysfunction, including Viagra (sildenafil) and Cialis (tadalafil) amongst others.

However, in some men, the issue isn’t as much an inability to get an erection, which can be a mechanical or biochemical issue but more of a combination of a lack of desire and willingness to engage in sexual activity. This can often be a cause of erectile dysfunction which stems from low testosterone.

In men with low testosterone, improving these levels to normal often results in a return to normal erectile function.

Increased muscle mass, strength and reduced body fat

There are lots of studies which demonstrate the impressive effects of testosterone on men’s muscle mass, strength and body fat levels.

It is something that most men who start testosterone notice – a dramatic change in their physique.

Testosterone is an effective mass builder by increasing the protein synthesis required for growth. It also improves neuromuscular function which results in strength increases. This is part of the androgenic effect of testosterone and includes the effects of DHT (dihydrotestosterone).

Men with higher testosterone levels tend to have lower overall visceral and abdominal body fat levels. Both of these things (when raised) are bad for overall health and lead to increased mortality rates.

However, TRT is not a magic bullet, whilst is does increase muscle very effectively, it will not shed body fat effectively on its own. A consistent workout regime and a healthy diet are paramount to improving this – testosterone does make the dieting process much easier for those who struggle to lose bodyfat.

Improved bone density

A common effect of low testosterone is reduced bone density. This is partly due to low testosterone and partly due to the reduction in oestrogen that results (as oestrogen is converted from testosterone in men).

Increasing testosterone levels improves bone density, particularly in the spine where older men often suffer from compression fractures.

The main effect on bone density is most likely driven by oestradiol levels, however this is mainly a byproduct of testosterone in men as it is converted by the aromatase enzyme.

As a result, men with low testosterone will have lower bone density, and increasing testosterone will improve oestrogen levels.

How long does it take for TRT to start working?

In most patients, the benefits of TRT take from 3 to 6 months to be fully realised. Some benefits, such as bone density, fat loss and muscle mass increases, will continue to improve for longer than 6 months.

Whilst most men notice some improvements early on in their TRT journey, there are lots of factors which affect the rate of progress.


Firstly, and most importantly, TRT is a process. Optimising testosterone replacement therapy takes time and you should work with your doctor to monitor blood results and adjust dosages. Often the dose you start on will cause testosterone and oestrogen levels to rise. This will dampen any benefits and may feel like testosterone is still low. Occasionally (much more rare) the dose is too low and patients need to increase it further to get levels into the optimal range. In both situations, a blood test is important to ensure careful adjustment of your dose by a specialist doctor.

Secondly, the type of testosterone preparation will cause variations in the time it takes for men to notice improvements. Something like propionate or sustanon (which contains propionate) will have a faster effect than something like nebido which takes longer to act in the body due to a longer ester attachment.

OptiMale doctors primarily recommend medium acting esters such as testosterone cypionate and testosterone enanthate which can take around 6 weeks to build up to their full testosterone levels in the blood. However, the benefits of testosterone replacement therapy for men who have lower levels may be seen before this build up happens.

Thirdly, some of these improvements take a while to be seen in the body. Usually mood and libido improvements take a few weeks to a couple of months to appear if the dosage is optimised and oestrogen levels are good. Other physique changes can take a lot longer.

Saad et al. (2011) researched the timescales for the effects of testosterone replacement therapy and found that:

Effects on sexual interest appear after 3 weeks plateauing at 6 weeks, with no further increments expected beyond.
Changes in erections/ejaculations may require up to 6 months.
Effects on quality of life manifest within 3–4 weeks, but maximum benefits take longer.
Effects on depressive mood become detectable after 3–6 weeks with a maximum after 18–30 weeks. 

You can read more on the timescales here.

Finally, there are individual factors which influence how long it takes for testosterone to show benefits.

The individual’s testosterone levels before starting treatment. If very low then the impact of adding testosterone may be felt more quickly.

Androgen receptor differences. Some men have less sensitive androgen receptors, often due to previous steroid abuse. Others naturally have more androgen receptors which will improve the response rate to testosterone levels increasing. Differences can be seen in CAG length, more info here.

Unknown factors. Some men are more sensitive to increases in testosterone and oestrogen. Others are genetically more susceptible to converting testosterone into oestrogen as they have more aromatase in their bodies. This can mean that the benefits of testosterone replacement therapy are less obvious.


This is a brief overview of some of the main benefits of TRT. To really notice these benefits you have to find specialist treatment using the correct medications.  In the UK these medications are often hard to come by, and aren’t readily provided by the public health system.
OptiMale uses the Gold Standard of TRT which is adapted to your individual circumstances and physiology to provide the best treatment options with the least possible side effects.
This includes the use of HCG for maintenance of fertility, natural production and the regulation of hormonal byproducts which are lost when using TRT on its own.
If you’d like to discuss treatment with us then please contact us on the form below for more information and expert advice.
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.