Testosterone Replacement Therapy (TRT): A Doctor-Led Guide to Low Testosterone in Men
A balanced, evidence-based overview of what TRT is, who it helps, what the latest research says about its safety, and how a responsible clinic assesses and monitors treatment.
Testosterone is the principal male sex hormone, but its role reaches far beyond libido. It influences muscle and bone strength, red-blood-cell production, mood, concentration, energy and sexual function. From roughly the age of 30, a man’s testosterone declines gradually — on average by around 1–2% per year — and for some men this fall, combined with other factors, produces troublesome symptoms. When low testosterone is confirmed on blood testing and is causing symptoms, testosterone replacement therapy (TRT) can be a genuinely effective treatment. It is, however, a prescription medical therapy that deserves careful diagnosis and ongoing supervision — not an off-the-shelf “anti-ageing” quick fix.
This guide explains low testosterone (sometimes called male hypogonadism, or the “male menopause” / andropause), how it is diagnosed, the treatment options, and — importantly — what the most recent and highest-quality evidence tells us about the benefits and the risks.
What is low testosterone?
Doctors use the term
hypogonadism
to describe the combination of consistently low testosterone levels
and
symptoms attributable to that deficiency. Both parts matter: a low number on its own, without symptoms, is not usually treated, and symptoms alone without a confirmed low level should prompt a search for other causes.
Hypogonadism is broadly divided into two types.
Primary
hypogonadism arises from a problem in the testes themselves (for example after injury, certain genetic conditions, or some cancer treatments).
Secondary
hypogonadism arises from the pituitary gland or hypothalamus in the brain not sending the right hormonal signals — commonly linked to obesity, type 2 diabetes, obstructive sleep apnoea, certain medications (including opioids and long-term steroids) and chronic illness. Distinguishing the two guides both treatment and any further investigation.
Recognising the symptoms
The symptoms of low testosterone are real but non-specific, which is exactly why proper testing matters — many overlap with stress, depression, poor sleep, thyroid problems and simply being unwell. Commonly reported symptoms include:
- ✓
Reduced sex drive and fewer spontaneous erections; erectile difficulties - ✓
Persistent fatigue, low energy and reduced stamina - ✓
Low mood, irritability, poor motivation and difficulty concentrating - ✓
Loss of muscle mass and strength; increased body fat, particularly around the abdomen - ✓
Reduced bone density, and sometimes hot flushes or disturbed sleep
Because these symptoms are shared with many other conditions, they should be a prompt to investigate — not a diagnosis in themselves.
How low testosterone is diagnosed
Accurate diagnosis is the foundation of safe treatment. Testosterone levels follow a daily rhythm and are highest in the morning, so blood should be taken
before 11 am, in the fasting state
, and a low result should be
confirmed on at least two separate occasions
. Guidelines from the Endocrine Society and the British Society for Sexual Medicine (BSSM) recommend measuring
total testosterone
first, and, where the total sits in a borderline range or a man has conditions that alter sex-hormone-binding globulin (SHBG), calculating
free testosterone
as well.
1,2
Where a deficiency is confirmed, further blood tests — luteinising hormone (LH), follicle-stimulating hormone (FSH), prolactin, SHBG, a full blood count and often a PSA (prostate) check — help identify the cause and establish a safe baseline. Reversible contributors, such as significant weight gain, poorly controlled diabetes, sleep apnoea or certain medications, should be addressed first, as they can improve testosterone without the need for lifelong therapy.
The Endocrine Society advises against population screening and recommends diagnosing hypogonadism only in men with
consistent symptoms and signs
plus
unequivocally and repeatedly low
morning total testosterone.
1
Assay variability and SHBG-altering states (obesity, diabetes, thyroid disease, nephrotic syndrome, ageing) make free-testosterone assessment — ideally by equilibrium dialysis or a validated calculation — important in borderline cases. LH/FSH differentiate primary from secondary hypogonadism; markedly low gonadotrophins with low testosterone, or high prolactin, warrant pituitary evaluation and imaging.
Treatment options
When TRT is appropriate, it can be delivered in several forms, and the choice is tailored to the individual’s preferences, lifestyle and response:
- ✓
Topical gels
applied daily to the skin — steady levels, easy to adjust, but require care to avoid transfer to partners or children. - ✓
Intramuscular injections
— shorter-acting preparations given every few weeks, or long-acting testosterone undecanoate given roughly every 10–14 weeks. - ✓
Other formulations
such as implantable pellets are used in some settings.
Crucially, TRT is rarely the whole answer. Weight loss, resistance exercise, better sleep, reduced alcohol and good control of conditions such as diabetes can meaningfully raise testosterone and improve symptoms — and remain important alongside any prescribed therapy.
What the evidence says about the benefits
The most rigorous evidence comes from the
Testosterone Trials (TTrials)
, a coordinated set of placebo-controlled studies in men aged 65 and over with low testosterone. Over one year, testosterone treatment produced consistent improvements in
sexual activity, desire and erectile function
, along with modest gains in
mood and depressive symptoms
and in
walking distance
. It also increased
bone density and strength
and corrected
anaemia
. Notably, it did
not
improve cognition or memory.
3
The honest summary is that, in the right patient, TRT can restore aspects of sexual function, energy and wellbeing and improve some objective measures — but it is not a cure-all, and the benefits are most reliable in men with a genuine, confirmed deficiency.
Is TRT safe? What the latest research shows
For years, the biggest question mark over TRT was cardiovascular safety. That question has now been addressed by the largest trial of its kind. The
TRAVERSE trial
(2023) followed more than 5,200 middle-aged and older men with low testosterone and existing or high risk of heart disease. It found that testosterone therapy did
not
increase the risk of major cardiovascular events (heart attack, stroke or cardiovascular death) compared with placebo.
4
On the strength of TRAVERSE and related studies, in
February 2025 the US Food and Drug Administration removed the boxed warning
about cardiovascular risk from testosterone products — while, importantly,
adding a new warning that testosterone can raise blood pressure
, which should be monitored.
5
This is reassuring, but it is not a green light for indiscriminate use: TRAVERSE also observed small increases in certain events such as atrial fibrillation, acute kidney injury and pulmonary embolism, and the therapy remains approved specifically for men with a diagnosed medical cause of low testosterone.
Other safety considerations that a responsible programme manages include:
- ✓
Blood thickening (raised haematocrit)
— the most common effect, requiring regular blood counts and occasional dose adjustment. - ✓
Fertility
— TRT suppresses the body’s own testosterone and sperm production, so it is generally avoided in men who wish to conceive; alternative approaches exist. - ✓
Prostate
— TRT does not appear to cause prostate cancer, but it can raise PSA and is not given to men with untreated prostate cancer; PSA and symptoms are monitored. - ✓
Bone and fractures
— although TRT improves bone density, a 2024 sub-study unexpectedly found
no
reduction in fractures, a reminder that surrogate measures do not always predict clinical outcomes.
6
TRAVERSE (n = 5,246) met its non-inferiority endpoint for MACE but flagged higher incidences of atrial fibrillation, acute kidney injury and pulmonary embolism in the testosterone arm.
4
Combined with the class-wide ABPM finding of increased blood pressure, this supports baseline and on-treatment monitoring of BP, haematocrit (withhold/adjust if >54%), PSA and symptoms, per Endocrine Society and BSSM schedules.
1,2
The T Trials fracture sub-study is a caution against extrapolating BMD gains to fracture-risk reduction.
6
Who should be cautious — and who should avoid TRT
TRT is not suitable for everyone. It is generally avoided in men with untreated prostate or breast cancer, a very high haematocrit, untreated severe sleep apnoea, uncontrolled heart failure, or a recent cardiovascular event, and in men actively trying to father a child. This is precisely why a thorough medical assessment — rather than a simple online questionnaire — is essential before starting.
Ongoing monitoring: what good care looks like
Starting TRT is the beginning of a supervised relationship, not a one-off prescription. A safe programme reviews symptoms and repeats key blood tests — testosterone level, full blood count (haematocrit) and PSA — typically at 3 and 6 months in the first year and then annually, alongside blood-pressure checks. Doses are titrated to restore levels to the mid-normal range, and treatment is continued only where there is clear, sustained benefit.
The PHP approach: anatomy first, judgement before technique, safety always
At PHP, low testosterone and andropause are assessed the way any serious medical condition should be: with a proper history, examination, correctly-timed blood tests interpreted against current guidelines, and a plan that addresses reversible causes before reaching for a prescription. Where TRT is genuinely indicated, it is prescribed and monitored by registered doctors, with the safety checks the evidence demands. The goal is not simply to raise a number, but to restore wellbeing safely and sustainably.
If you recognise the symptoms described here, the right next step is a considered medical assessment rather than self-diagnosis. Our team can arrange appropriate testing and talk you through whether TRT — or another approach — is right for you.
Book a confidential, doctor-led consultation to get properly assessed.
References
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.
J Clin Endocrinol Metab.
2018;103(5):1715–1744.
academic.oup.com/jcem/article/103/5/1715 - Hackett G, Kirby M, Rees RW, et al. The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice.
World J Mens Health.
2023;41(3):508–537.
wjmh.org (10.5534/wjmh.221027) - Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of Testosterone Treatment in Older Men (The Testosterone Trials).
N Engl J Med.
2016;374(7):611–624.
pubmed.ncbi.nlm.nih.gov/26886521 - Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE).
N Engl J Med.
2023;389(2):107–117.
nejm.org/doi/10.1056/NEJMoa2215025 - US Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products. 28 February 2025.
fda.gov - Snyder PJ, Bhasin S, Cunningham GR, et al. Testosterone Treatment and Fractures in Men with Hypogonadism.
N Engl J Med.
2024;390(3):203–211.
nejm.org/doi/full/10.1056/NEJMoa2308836 - NHS. The ‘male menopause’.
nhs.uk/conditions/male-menopause
This article is for general information and education only and does not constitute medical advice, diagnosis or treatment. Testosterone replacement therapy is a prescription medicine that must be assessed, prescribed and monitored by a qualified doctor. Always seek personalised advice from a registered healthcare professional before starting, stopping or changing any treatment.