Quick answer
What is testosterone replacement therapy used for?
Testosterone replacement therapy (TRT) treats confirmed male hypogonadism — low testosterone on two morning blood tests with matching symptoms. Options include daily gels (Testogel), patches, or injections every 10 to 14 weeks. TRT improves libido, mood, and muscle mass in deficient men but suppresses sperm production. Regular blood monitoring for PSA, haematocrit, and testosterone levels is required.
Testosterone replacement therapy (TRT)
Testosterone replacement therapy restores testosterone levels in men with confirmed hypogonadism — see our low testosterone guide for diagnosis criteria.
TRT is not cosmetic anti-ageing medicine. Used appropriately, it improves libido, energy, mood, muscle mass, and bone density in deficient men. Used inappropriately, it carries cardiovascular, fertility, and cancer surveillance obligations.
Who qualifies on the NHS
Criteria (general):
- symptoms consistent with androgen deficiency
- two low morning total testosterone results (or low calculated free T with symptoms)
- reversible causes addressed — obesity, sleep apnoea, opioids where possible
- no contraindications
- informed consent including fertility impact
Endocrinology referral for:
- age under 40 with hypogonadism
- elevated prolactin or pituitary symptoms
- primary testicular failure needing workup
- fertility preservation needed
Forms of TRT
Testosterone gels (Testogel, Tostran, Testavan)
Most common UK first-line:
- apply daily to skin — shoulders, upper arms, abdomen
- steady levels with daily use
- transfer risk — wash hands; cover skin; warn partners/children
Pros: easy dose adjustment, no injections
Cons: daily routine, transfer risk, skin irritation
Transdermal patches
Alternative if gel unsuitable — night-time application, skin reactions common.
Intramuscular injections
Nebido (undecanoate) — every 10 to 14 weeks — long-acting
Sustanon — shorter interval — more peaks/troughs
Pros: no daily application
Cons: clinic visits or self-injection training; fluctuating levels between doses
Oral testosterone
Restandol (testosterone undecanoate) capsules — taken with food. Less first-line in UK than gel/injection due to variable absorption.
Methyltestosterone — avoid — liver toxicity.
Implants and pellets
Subcutaneous pellets — rarely used on NHS now.
Monitoring schedule
| Test | Purpose | Frequency |
|---|---|---|
| Total testosterone | Dose adequacy | 3 months after start/change, then annually |
| Haematocrit/Hb | Polycythaemia | 3, 6, 12 months, then yearly |
| PSA | Prostate safety | Before start, 3–12 months, then per guidance |
| LFTs | Liver (oral forms) | As indicated |
| Lipids, HbA1c | Metabolic health | Baseline and periodic |
Target: mid-normal testosterone range with symptom improvement — not supraphysiological bodybuilding levels.
Side effects and risks
Common:
- acne, oily skin
- gynaecomastia
- fluid retention
- polycythaemia — raised red cells — may need dose reduction or venesection
- sleep apnoea worsening — screen before and during TRT
Fertility:
- azoospermia (no sperm) common on TRT — assume infertility while on treatment
- ** sperm recovery** variable after stopping — months to years
Cardiovascular:
- Debated in older men with frailty — TRT may help or harm depending on population — individual assessment
- Avoid in recent heart attack/stroke (usually 6 months) unless specialist agrees
Prostate:
- Does not cause cancer in men without it
- May accelerate existing prostate cancer — PSA monitoring mandatory
- Contraindicated in known prostate or breast cancer
Contraindications
- Prostate or breast cancer
- Desire for fertility without alternative plan
- Untreated severe sleep apnoea
- Haematocrit above threshold (often >0.54) uncontrolled
- Unstable heart disease
TRT and lifestyle
TRT works best combined with:
- weight management
- resistance exercise
- sleep apnoea treatment
- alcohol reduction
Some men improve enough on lifestyle alone to avoid or stop TRT.
Private and online TRT — cautions
Private clinics often prescribe with minimal monitoring or supraphysiological doses — risks:
- polycythaemia and thrombosis
- fertility destruction
- masked prostate pathology
- dependency without true deficiency
Use regulated prescribers with full monitoring if private route chosen.
Stopping TRT
Natural production suppressed — do not stop abruptly without plan:
- symptoms return quickly
- post-TRT hypogonadism may persist
- clomifene or hCG — specialist strategies to restart axis for fertility
Young men should bank sperm before TRT if possible.
Special situations
Diabetes: TRT may improve insulin sensitivity modestly — continue diabetes care.
ED: Improves libido; may need PDE5 inhibitors separately.
Older men: Higher baseline cardiovascular risk — shared decision-making essential.
TRT is effective medicine for true testosterone deficiency — success depends on correct diagnosis, realistic expectations, and lifelong monitoring, not quick-fix clinic marketing.
Common questions
- How is testosterone gel applied?
- Usually to shoulders, upper arms, or abdomen once daily at the same time — skin must be clean and dry. Allow to dry before dressing; wash hands thoroughly. Avoid skin contact with partners and children until dry — testosterone transfer causes hair growth or puberty signs in children if exposed.
- What are the side effects of testosterone replacement?
- Acne, oily skin, mood changes, fluid retention, breast enlargement, sleep apnoea worsening, and polycythaemia (thick blood). Injections may cause peaks and troughs — mood and energy fluctuation. Fertility drops — often reversible months after stopping in young men but not guaranteed.
- How often do I need blood tests on TRT?
- Typically at 3, 6, and 12 months after starting, then annually — check testosterone level (target mid-normal range), haematocrit, PSA, and liver function. Dose adjusted based on symptoms and levels — trough level before next injection for injectable forms.
- Can women use testosterone?
- Low dose testosterone is occasionally prescribed off-label for postmenopausal women with low libido (HSDD) — specialist only. Menopause HRT is different. Women must never use men's TRT products — virilisation (voice deepening, hair growth) occurs.
- Does TRT shrink the testicles?
- Yes — exogenous testosterone suppresses LH/FSH, reducing testicular activity and size over time. Reversible in many men after stopping but recovery is slow — months to years for fertility return.
- Can I stop testosterone replacement suddenly?
- Stopping causes return of hypogonadism symptoms as natural production is suppressed — may take months to recover. Taper under medical supervision; clomifene or hCG sometimes used to restart natural production in fertility cases.