What is Testosterone Replacement Therapy?

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Medically reviewed by Dr Chris Airey
BMBS MMedSc Dip ENDO, TRT Expert
iconLast updated 7th January 2022
In 30 seconds…

Testosterone Replacement Therapy is a treatment prescribed for men who are suffering from the symptoms of low testosterone, which include low energy, depression, and erectile dysfunction. It is also used in the management of hypogonadism, which can be primary (insufficient testosterone produced in the testes) or secondary (the brain doesn’t signal the testes to produce testosterone).

Low testosterone levels are diagnosed through a blood test and a consultation about your symptoms with your GP. Testosterone Replacement Therapy is used to “top up” your T-levels and treatment can be in the form of a patch, gel, or injection.

Testosterone is a crucial hormone in the male body. Produced mainly in the testes, its role goes beyond simply supporting your sex drive and fertility: testosterone is important for maintaining healthy muscle mass, bone density, and energy levels, too.

Bearing that in mind, it’s not surprising that low testosterone levels can lead to health problems. The good news is that treatment is available, in the form of Testosterone Replacement Therapy.

In this article, we take a frank look at the issue of low testosterone: the symptoms, how the condition is diagnosed and managed, and what Testosterone Replacement Therapy involves.

What are the Symptoms of Low Testosterone?

As men age, their testosterone levels gradually fall – at a rate of 1-2% per year from when they are 30 years old. This slow decline goes unnoticed by a lot of men and many will never experience any symptoms, meaning that treatment is probably not necessary.

Low testosterone levels (also known as “hypogonadism”) can also be caused by underlying health conditions that reduce testosterone production, such as those affecting the testes or pituitary gland. Other conditions behind low-T include type 2 diabetes and obesity.

If your T-levels get too low, this can start to produce some symptoms that are difficult to live with. Every man is different, but the symptoms of low testosterone can be physical, psychological, and sexual:

  • Physical symptoms include low energy, night sweats, decreased muscle mass, and loss of body and facial hair.
  • Psychological symptoms include depression, irritability, memory loss, and difficulty concentrating.
  • Sexual symptoms include loss of sex drive and problems achieving or maintaining an erection (erectile dysfunction).

It’s important to remember that these symptoms could also be the result of lifestyle choices (such as a poor diet or lack of exercise) or psychological issues such as stress or anxiety. But if you’re suffering despite those regular runs and kale smoothies, there’s no harm in getting your T-levels checked.

What are the Ideal Testosterone Levels?

If you’re concerned that you may have low-T, head down to your GP and ask for a blood test. To determine whether your testosterone levels are low enough to benefit from treatment, the doctor will consider various factors, including:

The time of the blood test: Your testosterone levels will be at their peak in the morning before 10am (though this is less pronounced in older men) and when you have not recently eaten.

The number of tests: One low result may not mean anything on its own, so it’s usually recommended that you have another test on a different day.

Your symptoms: The doctor will consider whether your symptoms suggest low testosterone levels.

The total amount of testosterone in your body: Usually levels of 12 nmol/L (nanomoles per litre of blood) or higher are considered “normal”. A T-level lower than this may require treatment, but it also depends on your symptoms.

The amount of “free testosterone” in your body: Not all the testosterone in your body is actually available for the body to use; therefore, your doctor will also separately consider your level of “free testosterone”.

If these factors indicate that your T-levels do need a boost to improve your health and wellbeing, then your doctor may suggest you consider Testosterone Replacement Therapy.

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What is Testosterone Replacement Therapy?

Essentially, Testosterone Replacement Therapy (TRT) does exactly what the name suggests: it tops up your testosterone levels with the aim of alleviating the symptoms you’ve been experiencing.

There are a few different methods of delivering the testosterone into your body:

  • A skin patch that’s applied to your upper body or arm usually once per day
  • A tablet that sticks to the upper gum in your mouth, applied twice per day
  • A gel that’s applied to the skin once daily
  • An injection into the muscle, usually every 2-4 weeks

Although oral testosterone pills are available, they are not recommended as there’s a risk of damage to the liver. All the methods of TRT above bypass the liver and send the testosterone straight into your bloodstream.

Whichever method of TRT you are prescribed, you’ll need to go for regular medical checkups to make sure your body is absorbing the right amount of testosterone from the treatment. You may need treatment over the long-term, if your body is no longer able to make enough testosterone on its own.

Does Testosterone Replacement Therapy Have Risks or Side Effects?

Many men report positive results from TRT. For example, one study reported that “testosterone replacement therapy improves quality of life, increases lean body mass, significantly decreases total cholesterol, and is well-tolerated and safe for men”.

However, before you decide to undergo TRT it’s important to consider the possible risks and side effects of treatment. Immediate side effects include:

  • A rash, itching, or irritation at the site where the testosterone patch or gel is applied (common)
  • Enlargement and tenderness in the breast area, acne, and disturbed breathing during sleep (rare)

TRT has also been associated with more serious risks, so it’s important to talk these through with your doctor before making a decision about treatment.


TRT carries a risk of causing an increased number of red blood cells in the body, which in turn can lead to blood clots.

Cardiovascular Health

Men receiving TRT over the long term may have an increased risk of cardiovascular problems, including strokes, heart attacks, and heart disease. It is important to have a free NHS health check or a formal cardiovascular risk assessment conducted by a medical professional before initiating TRT.

Prostate Issues

Testosterone can stimulate the prostate to grow larger, increasing the risk of Benign Prostatic Hypertrophy (where the urethra is squeezed by the enlarged prostate, making urination more difficult). Historically, it has been suspected that TRT can increase the risk of developing prostate cancer, but recent studies have questioned any direct association.

Note: TRT administered as a gel can also have negative effects on your female partner or children if they come into contact with it.

Key Takeaways…

When you’re experiencing the symptoms of low testosterone, there’s nothing wrong with getting your T-levels checked out. If it transpires that they’re fine then this could be a wake-up call to make some positive lifestyle changes, or consulting your doctor could flag up a different medical condition that needs treatment.

On the other hand, if it turns out that your testosterone levels are low, Testosterone Replacement Therapy could be the solution to treat your symptoms and give you a new lease of life.

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.

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