Testosterone Replacement Therapy (TRT): What It Is, Benefits, Risks and How It Works

Testosterone replacement therapy, commonly known as TRT, is a medical treatment used in men who have symptoms of testosterone deficiency alongside appropriately confirmed low testosterone levels.

Interest in testosterone has increased considerably in recent years, but symptoms such as tiredness, reduced sex drive, erectile difficulties or loss of strength do not automatically mean that you have low testosterone.

A proper assessment looks at your symptoms, medical history, blood results and possible underlying causes before deciding whether treatment is appropriate.

This guide explains what testosterone does, what can cause low testosterone, how testosterone deficiency is diagnosed, and what to expect if testosterone replacement therapy is being considered.

What is testosterone?

Testosterone is an androgen hormone produced mainly by the testes. Its production is regulated by signals from the hypothalamus and pituitary gland in the brain.

Testosterone is involved in several functions throughout the body, including:

• sexual desire and sexual function

• sperm production

• muscle mass and strength

• bone health

• body-fat distribution

• facial and body hair

• red blood cell production

• aspects of mood and general wellbeing

Testosterone levels are generally highest during adolescence and early adulthood and gradually decline as men get older. However, getting older does not automatically mean that a man has testosterone deficiency or needs TRT.

What is testosterone replacement therapy?

Testosterone replacement therapy (TRT) involves prescribing testosterone to men whose bodies are not producing enough of the hormone.

The medical term for testosterone deficiency is hypogonadism.

TRT is intended to restore testosterone into an appropriate physiological range and improve symptoms associated with confirmed testosterone deficiency. Licensed testosterone treatment for adult male hypogonadism requires testosterone deficiency to be supported by both clinical features and biochemical testing.

TRT should therefore not simply be viewed as a treatment for tiredness, ageing, poor gym performance or reduced motivation.

The first question is not:

“Would testosterone make me feel better?”

It is:

“Do my symptoms and blood results indicate testosterone deficiency, and why?”

Why might someone need TRT?

TRT may be considered when a man has symptoms consistent with testosterone deficiency and testing shows persistently low testosterone levels.

The underlying problem can originate in different parts of the hormonal system.

Primary hypogonadism

Primary hypogonadism occurs when the testes themselves cannot produce adequate testosterone.

Possible causes include:

• testicular injury

• previous testicular surgery

• certain genetic conditions

• chemotherapy or radiotherapy

• inflammation or damage affecting the testes

Secondary hypogonadism

Secondary hypogonadism occurs when there is a problem with the hormonal signals from the hypothalamus or pituitary gland that normally stimulate testosterone production.

Further investigation may therefore involve hormones such as LH, FSH and prolactin, alongside testosterone and other blood markers.

Other factors that can affect testosterone levels

A low testosterone result does not necessarily mean lifelong testosterone treatment is required.

Levels can also be influenced by factors including:

• obesity

• excessive alcohol intake

• certain medicines, including opioids

• previous anabolic steroid or testosterone use

• sleep disorders

• some chronic illnesses

• acute illness

Where a reversible factor is contributing to low testosterone, dealing with the underlying cause may be an important part of management.

What are the symptoms of low testosterone?

Symptoms vary between individuals, and many are not specific to testosterone deficiency.

Possible symptoms include:

• reduced sex drive

• fewer spontaneous or morning erections

• erectile difficulties

• fatigue or reduced energy

• reduced strength or exercise tolerance

• loss of muscle mass

• increased body fat

• reduced facial or body-hair growth

• low mood or irritability

• difficulty concentrating

• reduced motivation

• fertility problems

• loss of bone density over time

Sexual symptoms can be particularly relevant when assessing testosterone deficiency, but none of these symptoms alone proves that testosterone is the cause.

For example, fatigue, erectile dysfunction and low mood can also be associated with poor sleep, stress, obesity, cardiovascular disease, diabetes, depression, medication and other medical conditions.

That is why appropriate assessment matters.

How is low testosterone diagnosed?

Diagnosis should combine symptoms with biochemical testing rather than relying on symptoms or a single testosterone result alone.

Testosterone levels fluctuate during the day and are generally higher in the morning.

UK clinical guidance commonly recommends morning testosterone measurement, with an abnormal or borderline result repeated before confirming testosterone deficiency. The wider hormonal picture may then be investigated depending on the results and clinical history.

Testing may include:

• total testosterone

• sex hormone-binding globulin (SHBG)

• calculated free testosterone where appropriate

• luteinising hormone (LH)

• follicle-stimulating hormone (FSH)

• prolactin

• full blood count

• liver function

• prostate-specific antigen (PSA), where clinically appropriate

• other investigations according to symptoms and medical history

Finger-prick testosterone testing

A finger-prick testosterone test can provide a convenient initial screening step for some patients.

However, an isolated screening result should not automatically lead to testosterone treatment.

Where testosterone appears low or the clinical picture warrants further investigation, a formal venous blood test can be used to obtain a broader hormonal and health profile before a prescribing decision is made.

This distinction is important: testing testosterone is relatively simple; establishing why it is low and whether TRT is appropriate requires more clinical assessment.

What are the potential benefits of TRT?

For men with genuine testosterone deficiency, restoring testosterone to an appropriate physiological range may improve some of the symptoms associated with hypogonadism.

Potential benefits can include improvements in:

• sexual desire

• some aspects of sexual function

• muscle mass

• body composition

• bone density

• anaemia associated with testosterone deficiency

• general wellbeing in appropriately selected patients

The response varies considerably between individuals.

TRT should not be presented as a guaranteed way to increase energy, build muscle, lose fat, improve erectile function or reverse ageing.

Evidence for testosterone treatment is strongest when a patient has both clinically relevant symptoms and confirmed testosterone deficiency. The benefits of prescribing testosterone simply to counter normal age-related hormonal change are much less clear.

What are the risks and side effects of TRT?

Like any prescription medicine, testosterone can cause side effects and requires clinical monitoring.

Possible adverse effects can include:

• acne or oily skin

• increased red blood cell production

• raised haematocrit

• breast tenderness or enlargement

• fluid retention

• changes in prostate-related measurements

• reduced sperm production

• suppression of the body’s own testosterone production

• worsening of certain sleep-related breathing problems in susceptible patients

The increase in red blood cell production is particularly important. Haematocrit is therefore routinely monitored during testosterone treatment because excessive elevation may require dose adjustment, a change of preparation or stopping treatment.

Your individual cardiovascular, prostate, fertility and general medical history should also form part of the decision to start treatment.

Does TRT affect fertility?

Yes. This is one of the most important issues to discuss before starting testosterone.

Taking testosterone from outside the body can suppress the hormonal signals that stimulate the testes.

This can significantly reduce sperm production and may affect fertility.

For men who want to have children now or in the future, conventional TRT may therefore not be the appropriate first treatment. Alternative approaches or specialist fertility input may need to be considered.

Fertility plans should be discussed before, not after, testosterone treatment begins.

What types of testosterone treatment are available?

Several testosterone formulations exist.

In UK clinical practice these can include:

Testosterone gels

Testosterone gel is applied to the skin, usually every day.

It allows relatively straightforward dose adjustment but must be used correctly. Patients also need to follow precautions designed to prevent testosterone being transferred from the application site to another person.

Testosterone injections

Testosterone can also be administered by intramuscular injection.

Different preparations have different dosing intervals, so the frequency of treatment depends on the specific product being prescribed and the patient’s clinical requirements.

Other formulations

Other testosterone delivery systems have also been used, including implants and other formulations, although availability and routine use vary.

There is no universally “best” form of TRT.

Treatment choice should take into account factors such as:

• blood results

• clinical history

• response to treatment

• side effects

• convenience

• patient preference

• fertility considerations

• ability to monitor treatment appropriately

NHS patient guidance describes gels and intramuscular injections among the commonly used approaches to testosterone replacement in men.

How is TRT monitored?

Starting TRT is not the end of the process.

Monitoring is part of the treatment.

The objective is not simply to increase a testosterone number. The clinician needs to assess whether symptoms are improving, testosterone levels are appropriate and treatment is remaining safe.

Depending on the individual and the treatment used, monitoring may include:

• testosterone levels

• full blood count and haematocrit

• PSA where appropriate

• liver function

• blood pressure and cardiovascular risk

• treatment side effects

• sexual symptoms

• general clinical response

NHS guidance recommends continued monitoring during testosterone replacement, including assessment for changes in red blood cell count and prostate-related markers where appropriate.

The dose or formulation may need to change according to the results.

TRT should therefore be regarded as an ongoing prescribing and monitoring pathway, rather than a one-off prescription.

Who may not be suitable for TRT?

Testosterone is not appropriate for everyone.

A prescriber must consider the individual’s medical history, examination where appropriate, blood results and risk factors.

Particular caution or specialist assessment may be required in circumstances such as:

• known or suspected prostate cancer

• male breast cancer

• significantly elevated haematocrit

• untreated severe obstructive sleep apnoea

• severe or uncontrolled heart failure

• certain cardiovascular circumstances

• a desire to maintain fertility

The significance of each risk factor depends on the individual patient, so suitability should be determined through a proper clinical assessment rather than a checklist alone.

How long does TRT take to work?

TRT is not an instant treatment.

Different effects may develop at different rates, and response varies between patients.

Changes in sexual symptoms may become noticeable before changes in body composition or bone health. Some outcomes require months of treatment and appropriate follow-up before they can be meaningfully assessed.

Equally important, not every symptom will necessarily improve simply because testosterone levels increase.

If symptoms remain unchanged despite appropriate testosterone levels, the clinician should consider whether another condition or factor may be contributing.

This is another reason why treatment should be based on a proper diagnosis rather than testosterone being used as a general treatment for tiredness or reduced wellbeing.

Starting a testosterone assessment with Puri Pharmacy

At Puri Pharmacy, our testosterone pathway begins with assessment and testing rather than immediately prescribing treatment.

Patients can access the service either in person or through our remote pathway.

Step 1 — Initial assessment

We review your symptoms, relevant medical history, current medication, lifestyle, fertility plans and reasons for considering testosterone testing.

Step 2 — Initial testosterone testing

An initial finger-prick test may be suitable as a convenient screening option for some patients.

Step 3 — Comprehensive venous blood testing

Where appropriate, a full venous blood test is then used to investigate testosterone alongside the additional markers required to assess the wider clinical picture.

Bloods can be taken through our pharmacy service or arranged through an appropriate partner clinic depending on your location.

Step 4 — Prescriber review

Your results and symptoms are reviewed by a qualified prescriber.

Having a testosterone result below a laboratory reference range does not automatically mean TRT will be prescribed. We consider whether the results are consistent with testosterone deficiency, whether further investigation is necessary and whether reversible causes should be addressed first.

Step 5 — Treatment where clinically appropriate

If testosterone deficiency is confirmed and treatment is suitable, your prescriber can discuss the available treatment options, expected benefits, limitations, risks and monitoring requirements with you.

Step 6 — Ongoing monitoring

Patients receiving TRT require continued clinical review and blood monitoring.

Treatment may be adjusted according to testosterone levels, symptoms, side effects and safety markers.

Can I switch my existing TRT provider?

Yes.

Patients already receiving testosterone treatment elsewhere may be able to transfer their ongoing care to Puri Pharmacy.

We will still need to review your:

• diagnosis

• previous blood results

• current medication and dose

• treatment response

• monitoring history

• relevant medical information

Changing provider does not remove the need for appropriate clinical assessment and ongoing monitoring.

Frequently asked questions about TRT

Can I get TRT just because my testosterone is low?

Not necessarily.

A low testosterone result should be interpreted alongside symptoms, repeat testing where required, the time and circumstances of the blood test, other hormone results and your overall medical history.

Can I have normal testosterone but still feel symptoms associated with low testosterone?

Yes.

Fatigue, low libido, erectile dysfunction, reduced motivation and low mood can have many causes. If testosterone levels are normal, investigating alternative explanations may be more appropriate than testosterone treatment.

Does TRT help erectile dysfunction?

It can improve sexual symptoms in some men who have genuine testosterone deficiency.

However, erectile dysfunction has many possible causes, including cardiovascular disease, diabetes, medication, psychological factors and vascular problems. TRT is therefore not a universal treatment for erectile dysfunction.

Will TRT make me more muscular?

Testosterone has an important role in maintaining muscle mass, and treatment of genuine testosterone deficiency can affect body composition.

TRT should not, however, be prescribed as a bodybuilding or sports-performance treatment.

Is TRT the same as taking anabolic steroids?

No.

Medically supervised TRT aims to restore testosterone to an appropriate physiological level in someone with confirmed testosterone deficiency.

Non-medical anabolic-androgenic steroid use commonly involves different compounds and/or substantially different dosing strategies and carries its own health risks.

Will TRT increase my testosterone permanently?

TRT provides testosterone while treatment is being used. It does not necessarily correct the underlying reason your body is producing insufficient testosterone.

Treatment duration therefore depends on the cause of the testosterone deficiency and the individual clinical situation.

Is TRT safe long term?

Many men receive testosterone replacement over prolonged periods, but treatment requires appropriate patient selection and ongoing monitoring.

The potential benefits and risks should be reviewed individually, and emerging symptoms or abnormal blood results should not be ignored.

The important point about TRT

TRT can be an effective treatment for appropriately selected men with testosterone deficiency.

But good testosterone care starts before a prescription is written.

The correct pathway is:

Symptoms → assessment → appropriate blood testing → investigate the cause → clinical diagnosis → treatment if indicated → ongoing monitoring.

If you are experiencing symptoms that could be associated with low testosterone, the first step is therefore not necessarily starting TRT.

It is establishing whether testosterone deficiency is actually present and understanding what may be causing it.

Medical disclaimer

This article is provided for general information and does not replace individual medical advice, diagnosis or treatment. Testosterone is a prescription-only medicine in the UK. Whether testing or treatment is appropriate should be determined by a suitably qualified healthcare professional following an individual clinical assessment.