When your testosterone’s too low, it can feel like a part of you is missing. Testosterone replacement therapy (TRT) can help you get back on track, but there’s one big question that often crops up — what testosterone level should I be aiming for?
Contents:
- What’s a good total testosterone level on TRT?
- How long does TRT take to work?
- When should I take a blood test on TRT?
- What’s a good free testosterone on TRT?
- What if my testosterone levels go too high?
- Why aren’t my testosterone levels increasing?
Testosterone levels matter
One of the main goals of TRT is to get you back to feeling like yourself again. That’s why your symptoms — like low energy, poor libido, or flagging mood — play a key part in guiding your treatment.
But symptoms alone don’t tell the full story. If your testosterone isn’t sitting in the sweet spot, it could be doing more harm than good. Too low, and you might not be getting the full benefits. Too high, and you might develop side effects.
Target testosterone levels on TRT
Many UK labs class a total testosterone result as “normal” if it falls between 8–30 nmol/L. But we know that many men don’t feel their best if they’re lingering at the lower end of this range.
So, what’s an optimal target to aim for on TRT?
The British Society of Sexual Medicine (BSSM) states there’s not enough evidence to define an ‘optimal’ target, but recommends aiming for the mid-to-upper range (15–30 nmol/L) [1]. This is sometimes described as the ‘feel-good zone’ where most men feel their best. Equally, it’s not too high, which helps reduce the risk of side effects. Of course, this depends on when you take your blood test in relation to your dose.
Testosterone levels peak after TRT is taken and tend to trough before the next dose is due. It’s important to take your monitoring blood tests at the right time, which will depend on what type of TRT you take.
Timing of blood tests
The type of TRT you take — whether that’s injections, creams, gels, or tablets — will determine when it’s best to measure your testosterone level.
When to take your TRT monitoring blood test:
- Injections — take your test before your injection is due to get a trough level
- Creams and gels — take your test 2–4 hours after application
- Kyzatrex capsules — take your blood test 3–5 hours after your morning dose
By assessing trough levels for injectable TRT, your TRT specialist gets a better understanding of how long your treatment is effective for, so they can adjust the spacing between injections, or indeed the dose.
How long does TRT take to work?
Many men see a clear jump in their symptoms and testosterone level within the first 4–6 weeks. After that, levels tend to stabilise over the next 3–6 months.
Some men feel great very quickly; others need dosage tweaks or a different type of TRT to really hit their stride. That’s normal — no two bodies are the same.
What should free testosterone levels be on TRT?
Total testosterone (TT) is all the testosterone floating around in your bloodstream — it includes both the portion that’s bound to proteins and the portion that’s unbound (free).
Free testosterone (FT) is the biologically active portion that’s able to act on your tissues, and so it’s usually a more useful measure of your testosterone status.
There’s no formal guidance on ideal free testosterone levels while on TRT, but a good target to aim for is 0.4–0.62 nmol/L.
Some men can have a normal TT but a low FT due to high levels of sex hormone-binding globulin (SHBG), so your TRT specialist will check both to get the full picture. Based on this, your other biomarker results, and your symptoms, they’ll make a judgment call on whether your dose looks right.
What if my levels go too high?
Sometimes, you can overshoot. This isn’t a problem in the short term (it happens!), but a persistently raised total testosterone level above 30 nmol/L can cause serious problems. That’s why, at Leger, we don’t treat patients who wish to keep their testosterone levels beyond 30 nmol/L.
Overtreating with TRT can increase the risk of:
- Thicker blood and blood clots (raised haematocrit), including deep vein thrombosis (DVT), heart disease, and strokes
- Skin issues, like acne or oiliness
- Mood disturbances, including irritability
- Fluid retention or bloating
- Breast tissue enlargement (gynaecomastia)
Meanwhile, lingering at the lower end of normal, even if you notice some improvement, might not fully relieve some symptoms like tiredness. That’s why blood tests play a critical role in TRT.
Find out more about the risks of TRT.
Why aren’t my levels increasing?
Sometimes, even if you’re taking TRT right on schedule, testosterone levels don’t seem to want to budge. There are several potential causes for this.
Reasons testosterone levels aren’t increasing on TRT:
- Under-dosing — you might need a higher dose or more frequent injections
- Absorption issues — gels or creams might not be absorbing as expected due to excess hair or tattoos
- Injection site problems — improper injection technique could lead to poor absorption or the incorrect dose of testosterone
- Incorrect monitoring — if you take your monitoring blood test at the wrong time, it could make your levels appear falsely low
- Obesity — being overweight or obese significantly reduces the effectiveness of TRT by lowering overall testosterone levels
- Medical conditions — certain medical conditions, like hypothyroidism (an underactive thyroid), could affect the effectiveness of TRT
Why blood tests are crucial
TRT isn’t a set-and-forget situation. Even once you’ve been established on TRT long-term, you’ll still need to monitor your testosterone levels (albeit less frequently).
Blood testing gives you and your TRT specialist confidence that your treatment is optimised to keep you as free as possible from symptoms and side effects.
References
- Hackett G, Kirby M, Rees RW, Jones TH, Muneer A, Livingston M, et al. The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice. World J Mens Health. 2023;41: 508–537. doi:10.5534/wjmh.221027
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