Testosterone replacement therapy (TRT) can be life-changing for men with confirmed hypogonadism — but the first few months are often bumpier than many expect. Understanding what's normal, what requires monitoring, and what's a red flag is essential for anyone starting treatment.
This guide is written from a clinical perspective and covers the typical experience across the first 12 weeks of TRT. It's not intended to alarm — it's intended to prepare.
Why the First 3 Months Are an Adjustment Period
When you start TRT, your body — which has been running on low testosterone for months or years — suddenly has much higher hormone levels. At the same time, your endogenous testosterone production shuts down, your LH and FSH levels drop, and your body is adapting to an entirely new hormonal environment.
This transition period explains why some men feel better immediately, some feel worse before they feel better, and some don't notice full benefits until 3–6 months in. It's not a sign that TRT isn't working — it's the adjustment phase.
Common Side Effects and When They Typically Occur
| Side Effect | When It Typically Occurs | Usually Resolves? |
|---|---|---|
| Mood fluctuations / emotional ups and downs | Weeks 1–6 | Yes, usually by week 8–12 |
| Acne and oily skin | Weeks 2–8 | Often settles; persists in some |
| Injection site reactions (soreness, redness) | After each injection | Lessens with technique |
| Testicular atrophy (shrinkage) | Weeks 4–12 | Persists on TRT; reverses if stopped |
| Water retention / slight weight gain | Weeks 1–4 | Usually settles |
| Elevated haematocrit (thicker blood) | Months 1–3 | Monitored with blood tests |
| Reduced sperm count | Weeks 4–12 | Reverses when TRT stopped (usually) |
| Breast tenderness or mild gynaecomastia | Variable | Often resolves; dose adjustment may help |
Side Effects That Need Monitoring — Blood Tests Are Essential
TRT is safe when properly supervised. The key reason we monitor with blood tests at 6 weeks, 3 months, and 6 months is to catch changes before they become problems.
Haematocrit / Polycythaemia
TRT stimulates red blood cell production. If haematocrit exceeds 54%, blood thickens and cardiovascular risk increases. We check this at every monitoring appointment. Dose reduction or therapeutic phlebotomy resolves it.
PSA (Prostate Specific Antigen)
TRT can unmask pre-existing prostate conditions. We check PSA before starting and at every monitoring visit, particularly in men over 40. A rising PSA warrants further investigation.
Oestradiol (Estrogen)
Testosterone can aromatise to oestrogen, particularly in men with higher body fat. Elevated oestradiol causes breast tenderness, water retention, and mood changes. Blood test-guided dose adjustment resolves this.
Liver Function
More relevant with oral testosterone formulations, but we monitor liver function as standard. Injectable and transdermal TRT have minimal hepatic impact at therapeutic doses.
Red Flags — When to Contact Your GP Urgently
These are uncommon but require immediate attention:
- Chest pain, shortness of breath, or palpitations — seek emergency care
- Leg pain, swelling, or redness — possible deep vein thrombosis
- Severe headaches or visual changes — may indicate raised haematocrit
- Difficulty urinating — possible prostate enlargement
- Significant aggression or mood change — dose review needed
None of these mean TRT is the wrong treatment — they mean your dose or formulation needs reviewing.
The Timeline: What Most Men Experience
Why GP-Supervised TRT Matters
The side effects covered above are largely manageable — but only if they're caught. Men who source TRT without medical supervision miss the monitoring that prevents these issues from developing into real problems.
At Lambert Medical, our TRT protocol includes:
- Baseline bloods before starting (testosterone, SHBG, haematocrit, PSA, liver, lipids)
- Blood test review at 6 weeks after starting
- 3-monthly monitoring for the first year
- 6-monthly monitoring once stable
- GP available to discuss any symptom between appointments