TRT side effects, what is normal, and the red flags

Most TRT side effects are mild, predictable, and manageable. A few are more serious and need quick clinical attention. This article lists what to expect, what to manage yourself, and when to message us or go to A&E.

Common and usually manageable

Skin oiliness and acne (30 to 40 percent in first few months). Particularly on back, chest, and shoulders. Management: good skin hygiene, benzoyl peroxide wash, topical retinoid if persistent. Usually settles as the body adapts but can be ongoing in men who had adolescent acne. Rarely severe enough to stop treatment.

Injection-site reactions (10 to 15 percent for injectable users). Small area of redness, tenderness, sometimes a palpable lump for a few days. Management: rotate sites, keep injection depth adequate (deep IM into gluteal muscle is more comfortable than into fat), warm compress if sore. Reactions lasting more than a week or significantly painful swelling need review.

Gel application-site reactions (5 to 10 percent for gel users). Mild redness or dryness. Management: rotate between shoulders and upper arms daily, moisturise around the area. If severe or persistent, switch gel brand or consider injection instead.

Mild fluid retention (10 to 20 percent in first month). Feeling puffier, wedding ring tighter, slight ankle swelling. Usually settles by week 4 to 6. Management: reduce salt, monitor weight. Significant or persistent fluid retention may need dose adjustment or anastrozole addition if driven by E2 rise.

Mood shifts (variable). Usually improves, occasionally destabilises. Some men report feeling more assertive or short-fused in the first weeks; others feel more stable. Injectable regimens with marked peak-trough variation can produce mood rhythm; solutions are dose smoothing or switch of form.

Increased gym performance and appetite. Welcome usually. Requires corresponding increase in quality training and protein intake to convert to muscle rather than weight.

Sleep changes. Usually better. A minority of men sleep worse because of unmasked sleep apnoea or because of evening hormone peaks from gel application; we adjust timing if needed.

Testicular shrinkage. Expected and physiological. The degree varies. Low-dose HCG can preserve testicular size if cosmetic preservation matters.

Reduced fertility. Covered fully in the fertility article. Not a side effect to be surprised by if you have had the pre-treatment conversation.

Less common but worth knowing

Haematocrit rise (10 to 20 percent over the first year). Expected. Significant rise (over 0.52) needs attention. Covered in the haematocrit article.

Gynaecomastia (5 to 10 percent). Feeling of tenderness behind one or both nipples, sometimes a palpable tender firmness. Related to E2 rise. Management: low-dose anastrozole if persistent. Occasionally persists as chronic; surgical correction is rare but available.

Sleep apnoea worsening (5 to 10 percent). TRT can modestly worsen upper airway collapse in men with baseline apnoea. If partner reports worsening snoring or witnessed apnoeas, we check with a WatchPAT study and refer for CPAP if needed.

Increased aggression or irritability (5 percent, usually dose-related). More often reported by partners than by the man himself. Sign of supraphysiological dosing; response is dose reduction.

Reduced testicular volume with subfertility concern. Sometimes reversible on stopping, not always. See fertility article.

Cholesterol shifts. Usually modest improvement in hypogonadal men. In some, HDL can fall; monitored annually.

Rare but serious - message us or contact urgent care

Chest pain, severe chest tightness, shortness of breath. Possible cardiac event. 999. This is extremely uncommon on TRT in men without established coronary disease but is always the first line of red-flag advice.

Severe leg pain, unilateral calf swelling, redness. Possible deep vein thrombosis. Same day review via NHS 111 or A&E.

Severe breathlessness, collapse, or coughing up blood. Possible pulmonary embolism. 999.

Sudden severe headache, vision changes, fainting. Investigate for raised blood pressure crisis or other serious cause. Same day review.

Severely rising blood pressure not responsive to usual medication. Contact us or your GP within days.

Skin yellowing, dark urine, severe right upper abdominal pain. Rare, relates to oral preparations specifically. Stop medication and seek review.

Severe mood changes or suicidal thoughts. We treat this as urgent. Contact us or NHS 111. We may pause TRT and reassess.

Specific to injectable regimens

Injection-site infection: redness spreading beyond injection site, fever, significant swelling. Seek medical review promptly.

Oil embolism (extremely rare, associated with inadvertent intravenous injection of oil-based preparations): cough, chest tightness during or immediately after injection. Call 999. Prevention: aspirate before injecting.

Severe injection-site pain lasting more than 5 days: unusual, worth review.

What counts as "please contact us within the week"

Persistent haematocrit rise, PSA rising faster than expected, mood changes that have not settled, significant gynaecomastia, injection-site reactions not settling, sustained fluid retention, worsening sleep or apnoea symptoms. None of these are emergencies but they need management.

What counts as "we can wait until your next routine review"

Mild persistent skin changes, modest peak-trough mood variation on injectable regimens, minor injection-site bruising, slight weight gain, minor hair changes, mild changes in facial appearance (slightly fuller jaw from fluid balance), slightly earlier-pattern hair loss in men with androgenetic alopecia tendency (testosterone drives hair loss in susceptible men; we will discuss this at assessment and monitoring).

How we support you between reviews

Unlimited secure messaging is included in all our ongoing-care plans. We respond within one working day. Urgent queries (symptoms that may not wait) get priority. Most questions can be resolved by message; where a review is needed we offer same-week video or in-person as appropriate.

The honest bottom line

TRT is safe when properly monitored. Most side effects are mild and manageable. A small number are serious and predictable enough that we screen for them systematically. The point of regular monitoring is not bureaucratic; it is to catch the things that matter while they are still easy to fix.

Ready to start?

If this article has made you think an assessment might help, the next step is a short consultation with one of our men's health doctors.

Begin your consultation at this link. Online or in person at Westfield London.