Different organisations set different thresholds for treating low testosterone, and the guidance itself varies. That is why it is entirely possible to be told your levels are normal by one service and still be eligible with us. Our approach is based on the BSSM (British Society for Sexual Medicine) guidelines and on the most up-to-date research.
It is not only about the numbers
Whether treatment is appropriate depends on your symptoms as well as your blood results. Two men with the same reading can get different answers: someone with clear symptoms and a borderline result may well be suitable, while someone with no symptoms and the same result may not be. Your doctor looks at both together.
How the thresholds compare
- The NHS generally treats at a total testosterone below 8 nmol/L, and sometimes lower.
- BSSM's published thresholds are a total testosterone of 12 nmol/L and a free testosterone of 0.225 nmol/L. You can read the guideline in full in the British Society for Sexual Medicine's guidance on male adult testosterone deficiency (World Journal of Men's Health, 2023).
- Ours are 15 nmol/L and 0.35 nmol/L — wider than both, so that we can treat men who have symptoms but fall into the borderline range.
The NHS also typically measures only total testosterone. Some men, particularly older patients or those in poorer health, have a low calculated free testosterone even when their total testosterone looks normal, and that can be missed.
The levels we work to
We look at both total testosterone and free testosterone, and the thresholds depend on your age.
- 30 and over: total testosterone below 15 nmol/L, or free testosterone below 0.35 nmol/L. Either one on its own is enough.
- Under 30: the stricter BSSM figures apply — total testosterone below 12 nmol/L and free testosterone below 0.225 nmol/L. The route is different for under-30s as well.
One exception worth knowing about. If your total testosterone is above 18 nmol/L you are not eligible for TRT, even if your free testosterone is below 0.35 nmol/L. This is the part that catches people out, because a low free testosterone reading on its own can look like it should qualify. Your doctor may still discuss other options with you, such as Tadalafil.
If your total testosterone comes back between 15 and 17 nmol/L with free testosterone of 0.35 nmol/L or below, we will send you a retest kit free of charge rather than leave it on a single borderline reading.
Our tests are clinically valid
Our blood tests are processed by our laboratory partners, and the results are clinically valid. Where we differ from the NHS is in the thresholds we treat at, not in the quality of the testing.
Our eligibility criteria changed in December 2025. If you were told previously that you were not eligible, it is worth asking us to look again.
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