---
title: "Testosterone replacement therapy: Uses & Side Effects"
description: "NHS testosterone replacement therapy (TRT) — gels, patches, and injections for hypogonadism: who qualifies, monitoring, side effects, and fertility…"
url: https://healthanswers.co.uk/treatments/testosterone-replacement-therapy/
robots: noindex
---

# Testosterone replacement therapy: Uses & Side Effects

Treatments

NHS testosterone replacement therapy (TRT) — gels, patches, and injections for hypogonadism: who qualifies, monitoring, side effects, and fertility warnings.

Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 3 July 2026

## 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.

## Who is this page for?

This page is for people in the UK who want a plain-English overview of Testosterone replacement therapy, including when to seek help and what NHS care usually involves. It explains general information, not what is wrong with you personally.

## Who should skip this page?

Skip this page if you need a diagnosis, a prescription, or emergency care. It cannot replace a GP, pharmacist, NHS 111 or 999. If you are in immediate danger, call 999; for urgent advice that is not life-threatening, call 111 in England, Scotland or Wales, or use your GP out-of-hours service in Northern Ireland.

On this page 10 sections

## Key facts about testosterone replacement therapy

- TRT is only for diagnosed hypogonadism — not for anti-ageing in men with normal levels.
- Testosterone gels must not transfer to partners or children — wash hands after application.
- TRT suppresses natural sperm production — discuss fertility before starting.
- Polycythaemia (raised haematocrit) is a common side effect — monitored by blood tests.
- Treat reversible causes (obesity, sleep apnoea) before or alongside TRT.

## Testosterone replacement therapy (TRT)

**Testosterone replacement therapy** restores testosterone levels in men with **confirmed hypogonadism** — see our [low testosterone](https://healthanswers.co.uk/conditions/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](https://healthanswers.co.uk/treatments/sildenafil-and-tadalafil/) 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.

## ! Important safety information for testosterone replacement therapy

TRT requires GP or endocrinology supervision — never use unregulated online testosterone. Seek urgent help for chest pain, leg swelling, or breathlessness (possible clot). Report erections lasting over 4 hours, severe mood changes, or symptoms in partners/children after gel contact. Annual prostate assessment as advised.

## Common questions about testosterone replacement therapy

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.

## Sources

- [NHS — Male menopause](https://www.nhs.uk/conditions/male-menopause/)
- [BSSM — UK guidelines on testosterone deficiency](https://www.bssm.org.uk/)