Generally, in the UK, clinically low testosterone is considered to be anything below 9nmol/l. However, it’s important to note that many men will still develop symptoms of a deficiency with far higher testosterone levels. There can be various factors at play here, such as differences in hormone sensitivity. BSSM guidelines state 12nmol/l and below for a testosterone deficiency. However, this fails to factor in things such as Free T levels, SHBG, LH, FSH and also symptoms, medical history. These can all play a part in diagnosis, even if testosterone levels appear ‘normal’.