“I’m knackered and my gym mate says it’s low testosterone — can I just get a T boost?”

Fatigue with low libido in a young man has many causes, and testosterone deficiency is an uncommon and heavily over-attributed one — so resist the "just test it and give me a T boost" request (driven by online "low-T" content and gym culture) and work the fatigue up structurally, screening sleep/insomnia/OSA (NICE NG202), mood/depression with a direct self-harm question (NICE NG222) and stress, diet, overtraining/under-recovery, alcohol/drugs, anaemia, thyroid disease and diabetes, as for any "tired all the time" presentation. If symptoms genuinely suggest HYPOGONADISM (low libido, erectile dysfunction, reduced morning erections, low energy/mood, reduced muscle mass, gynaecomastia, small testes), confirm it CORRECTLY (BSSM guideline, Hackett et al 2023): two MORNING (7–11am, ideally fasting) total testosterone samples on separate occasions (levels vary and fall with acute illness and through the day), with LH, FSH, SHBG (± calculated free testosterone), prolactin and FBC — not a single random level — with a confirmed low result needing explanation (primary vs secondary) and usually specialist/endocrine input. Crucially, bust the MYTH that testosterone is a fatigue/energy/performance tonic and that "where’s the harm in trying" is safe: giving testosterone to a man with normal levels (or self-sourced anabolic steroids) is harmful, suppressing endogenous testosterone and sperm production to cause INFERTILITY (the most underestimated harm in young men) and testicular atrophy, plus polycythaemia (thrombosis/stroke risk), gynaecomastia, mood/cardiovascular effects, with unregulated, potentially contaminated gym/online products. Ask NON-JUDGEMENTALLY about current/considered gym or online testosterone, anabolic steroid, "booster" or SARM use, as it is common, may itself be causing his symptoms (post-cycle hypogonadism), and matters for safe management and harm reduction (needle and syringe programmes include people who inject image- and performance-enhancing drugs — NICE PH52, 2014). Take the fatigue and low libido seriously, educate honestly without being dismissive or preachy, treat the actual cause, and reserve testosterone replacement for genuine, correctly-confirmed hypogonadism with specialist input.