Testosterone is a vital hormone in the male body. It supports your sexual function and regulates your muscle mass, energy levels, and mood. As such, when testosterone levels are below the healthy range, it can have wide-ranging implications that affect many bodily functions.

Men with low testosterone often seek treatment through testosterone replacement therapy (TRT). TRT is the administration of the testosterone hormone into the body to replace low levels of natural production. At first glance, the benefits of testosterone therapy look too good to be true: improved physique, better mood, better sex, more confidence, and better overall health.

If you have only just heard about TRT, you’d be forgiven for being sceptical about the above claims. Here we set the record straight, explaining what benefits you can expect and how long it will take you to see results from your treatment.

What are the benefits of testosterone replacement therapy?

The main purpose of testosterone replacement therapy is to restore healthy blood testosterone levels. Doing so reverses the effects of low testosterone and may carry the following benefits:

• Improved mood and cognition
• Stronger libido (sex drive)
• Improved assertiveness and confidence
• Ability to get and maintain erections for longer
• Better sleep quality
• Increased muscle mass and bone density
• Improved beard growth
• Better vascularity and blood supply
• Deeper and more stable voice

However, whether you’ll experience these improvements largely depends on your overall health and whether you suffer from negative symptoms in this area before you begin treatment. Below are some research-backed examples to illustrate this point.

1. Improved mood

Jung and Shin (2016) demonstrated that TRT can improve mental health in men with testosterone deficiency. After eight months of treatment, men receiving testosterone therapy had significantly improved depression scores. Of course, everyone has down days, but if you’re feeling lower than usual, TRT may help boost your mood. 

However, not everyone with low testosterone suffers from depression. Some research suggests it is a more likely symptom in men with hypogonadism, whereas men with an age-related testosterone decline are less likely to struggle with low mood. Whether or not TRT will positively impact your mood could depend on the underlying cause of your deficiency.

2. Improved cognition

The 2016 study also found improved cognitive function, but only in patients suffering from ‘brain fog’ before treatment began. Brain fog is when men struggle to perform simple mental arithmetic, remember recent events, and find concentrating difficult.

Therefore, TRT could make you feel sharper and improve your mental acuity and memory. Interestingly, the researchers hypothesise how this could benefit men with other conditions, such as mild Alzheimer’s. This is a fascinating finding and something that needs further research.

3. Improved libido (sex drive)

Your testosterone levels increase naturally when you’re sexually aroused. Therefore, it is unsurprising that TRT can help improve your libido and get you ‘in the mood’. Several studies support this claim, finding that TRT causes improvements in sexual desire and erection quality. Even regular application of a testosterone gel was found to significantly improve sexual function in a large study of 840 men. 

However, there is a maximum level of testosterone, after which you see no improvement in libido. If you don’t have hypogonadism, increasing your testosterone levels further is unlikely to benefit your libido, erection quality, and sex life.

4. Improved erectile function

Normal testosterone levels are not necessary for normal erections. Erectile dysfunction (ED) often results from an underlying health problem preventing blood flow to the penis rather than hormonal imbalances. But in some men, the issue is less about an inability to get an erection and more about a lack of desire and willingness to engage in sexual activity. 

This can often cause erectile dysfunction which stems from low testosterone. In hypogonadal men, returning their testosterone levels to normal usually improves erectile function – but only if there is no other underlying cause of ED.

5. Increased muscle mass & reduced body fat

If there is one thing that most men who start testosterone replacement therapy notice, it’s a dramatic change in their physique. Lots of studies demonstrate the impressive effects of testosterone on muscle mass and body fat levels.

Indeed, research shows that TRT can help you lose weight and grow more muscle. Testosterone is an effective muscle mass builder that promotes protein synthesis and increases the number of calories you burn. However, TRT is not a magic bullet; it will not shed body fat effectively on its own. A consistent workout regime and a healthy diet are paramount to improving your body composition.

6. Stronger bone density

Reduced bone density is a common symptom of low testosterone. Increasing testosterone levels improves bone density, particularly in the spine. Hip bones also became stronger in older men on TRT. The main effect on bone density is most likely driven by oestradiol levels, as the body converts testosterone to oestradiol.

Yet while studies and trials show a clear improvement in bone strength, we don’t know whether TRT can help reduce the risk of fractures.

Can TRT improve your lifespan and prevent ageing?

TRT cannot reverse ageing, and treating normal ageing with testosterone therapy isn’t advised. If you don’t have declining testosterone levels, pumping more of this hormone into your body isn’t going to supercharge your vitality and keep you young. Regular exercise and a healthy diet are the best way to look after your health as you age.

However, the story is entirely different when it comes to TRT and lifespan. In a large study, men treated with testosterone replacement therapy were 24% less likely to have a heart attack and 36% less likely to have a stroke. Heart disease and strokes are among the leading causes of death globally. By having a healthy hormonal balance, you may live a longer life.

How long does it take for TRT to start working?

Whilst most men notice some improvements early on in their TRT journey, the benefits of TRT take three to six months to be fully realised. Some benefits – such as increased bone density, fat loss, and muscle mass increases – will continue to improve for longer than six months.

The time it takes to see improvements depends on the benefits you’re referring to. Below is a rough timeline for testosterone replacement therapy effects:

• Effects on sexual interest appear after three weeks plateauing at six weeks. You should expect no further increments beyond this point.
• Effects on quality of life manifest within three to four weeks, but maximum benefits take longer.
• Effects on depressive mood become detectable after three to six weeks. The maximum impact is reached by 18 to 30 weeks, with no further improvements.
• It may take up to six months to see improvements in erections and ejaculations.

What factors affect how quickly you feel the benefits of TRT?

• Type of testosterone: The type of testosterone preparation affects the time it takes for you to notice improvements. We primarily recommend medium-acting drugs such as testosterone cypionate, which take around six weeks to build up to its full testosterone levels in the blood. 
• Pre-treatment testosterone levels: How low your testosterone levels are before you begin treatment can impact the speed at which you see benefits. If you have very low or no testosterone, the impact of TRT is often felt more quickly. 
• Androgen receptor differences: Some men have less sensitive testosterone receptors, often due to previous steroid use. Others naturally have more androgen receptors which will improve the response rate to testosterone levels increasing.
• Unknown factors: Some men are more sensitive to increases in testosterone and oestrogen. Others are genetically more susceptible to converting testosterone into oestrogen, which can mean that the benefits of testosterone replacement therapy are less noticeable.

What if I don’t see any improvements?

If you don’t feel any better after you’ve started your treatment plan, speak to your doctor. They’ll be able to adjust your dose and preparation until reaching an optimal TRT protocol that suits you and your lifestyle – and brings all the promised benefits.

It’s important to remember that testosterone replacement therapy is a journey, and optimising your treatment takes time. Often the dose you start on will cause testosterone and oestrogen levels to rise. This will dampen any initial benefits, and you may feel that your testosterone levels are still low. Occasionally, the dose is too low and needs to be increased for you to feel the results.

Key Takeaways…

Testosterone replacement therapy can improve mood, body composition, sexual function, and bone density in men with low testosterone. To notice these benefits, you must find specialist treatment using the correct medications and work with your doctor to find an optimal protocol.

If you’re dealing with the symptoms of low testosterone, it’s a great idea to have your levels checked to see if TRT can initiate a positive change. It really can help you feel like yourself again and restore your vitality. However, TRT isn’t a magic anti-ageing cure that can help healthy men stay younger and supercharge their sex lives. Unless you have low testosterone levels initially, adding more testosterone into your body will have a limited impact.

While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.