If you are starting testosterone replacement therapy (TRT), or already on it and wondering why your dose looks different from someone else's, the short answer is that TRT dosing is individualised by design. There is a licensed starting point for each product, but where you land after that depends on your blood results, your symptoms and how your body responds, not on a fixed number that applies to everyone. This guide sets out how clinicians actually set, check and adjust a TRT dose in UK practice.
Why there is no single correct TRT dose
TRT dosing is individual because the goal is not to hit one universal number, it is to bring your own testosterone into the mid-normal range while relieving your symptoms, without causing side effects such as a raised haematocrit. Two men on the same product can end up on different doses because their baseline levels, body weight, how quickly they metabolise the medication and how their blood responds all differ.
This is also why a dose that works well for someone else, or a dose you read about online, is not a sensible target to aim for. British Society for Sexual Medicine (BSSM) guidance, which UK TRT services generally follow, frames dosing as a process of starting at a licensed dose and then titrating against blood results and symptom review at 3 and 6 months, rather than prescribing a single fixed amount from day one.
Typical starting doses by product
Starting doses follow the British National Formulary (BNF) and each product's own licence. They differ quite a lot between formulations, which is one reason TRT doses are not directly comparable across products:
- Testogel (gel). A common starting dose is two pump presses, roughly 40.5 mg, applied once daily to clean, dry skin. Our guide to testosterone gel for TRT covers Testogel, Tostran and Testavan dosing in more detail.
- Sustanon 250 (injection). Typically given as an intramuscular injection roughly every 3 weeks, since it is a blend of four testosterone esters designed to even out levels across that interval.
- Nebido (injection). Dosed on a longer loading schedule than Sustanon, reflecting its long-acting ester, then settling into a wider maintenance interval once levels are established. See our comparison of injectable testosterone products for how the schedules differ.
Whichever product you start on, the dose and interval your clinician prescribes should sit within that product's licensed range, adjusted for your baseline bloods. A provider proposing a dose well outside the product licence, without a clear clinical reason discussed with you, is a reason to ask more questions.
When blood levels are checked, and why timing matters
Where in the dosing cycle your blood is drawn changes what the result actually tells your clinician, so timing is not just a formality:
- On gel. Testosterone is usually measured 2 to 4 hours after application, which is roughly when gel-based levels peak, giving a meaningful read on how well that daily dose is working.
- On injections. A trough level, taken just before your next injection is due, shows the lowest point your testosterone falls to between doses. This matters because a trough that is still too low suggests the interval may need shortening, even if a mid-cycle reading would have looked fine.
A reading taken at the wrong point in the cycle, for example straight after a gel application rather than hours later, or the day after an injection rather than at the trough, can look misleadingly high and lead to an unnecessary dose reduction. This is part of why home test timing instructions matter, and why unusual results are often repeated at the correct time before any dose change is made. Our full guide to TRT blood tests covers the wider panel, not just testosterone itself.
What clinicians are aiming for
The target is testosterone in the mid-normal range for your age, alongside genuine improvement in the symptoms that led you to seek treatment, such as low mood, fatigue or reduced libido. Aiming for the mid-range rather than the top of it is deliberate: it gives room to adjust upward later if needed, while keeping the starting risk of side effects, particularly a raised haematocrit, as low as reasonably possible.
Symptom improvement is checked at the same time as the blood result, not instead of it. A level that looks correct on paper but comes with no symptom improvement, or symptom improvement that comes with a level pushing toward the top of the range, both prompt a closer look rather than being left alone.
How and when your dose is changed
Dose changes are made on blood results and symptoms together, reviewed formally at 3 months after starting or after any change, again at 6 months, then every 6 to 12 months once you are stable. A few scenarios account for most adjustments in practice:
- Trough or mid-cycle level too low. The dose may be increased, or the interval between injections shortened, within the product's licensed range.
- Level consistently too high, or haematocrit rising. The dose may be reduced, or the interval between injections lengthened.
- Haematocrit above around 54%. This is treated as a safety threshold. A clinician will typically lower the dose, space out injections further, or pause treatment altogether until it settles, then re-test before continuing. In some cases venesection, a blood donation-style procedure, is arranged alongside a dose change.
Every dose change should come with a plan for when it will be re-checked, usually at the next scheduled bloods rather than immediately, since testosterone and haematocrit take time to settle after an adjustment. For more on how often injections themselves are given and what each monitoring appointment covers, see our guide to testosterone injections for TRT.
Why you should never adjust your dose yourself
It can be tempting to take an extra pump of gel on a low-energy day, or bring an injection forward because symptoms have crept back before the next one is due. Doing this without a blood test and clinical review risks pushing your testosterone to supraphysiological, above-normal levels, which raises the risk of side effects including a thickened blood count, mood changes, acne and, over time, further suppression of your body's own hormone production, without reliably improving how you feel.
If a dose genuinely does not seem to be working, the useful step is to raise it with your clinician, ideally with a note of when symptoms are worst relative to your last dose, rather than experimenting with timing or amount yourself. That detail helps your clinician decide whether the issue is the dose, the interval, or something unrelated to TRT altogether. Understanding what your dose is actually costing you, and whether a different product might suit you better, is also worth factoring in; our TRT cost guide breaks this down by provider.