The most common causes of erectile dysfunction (ED) as per European Association of Urology (EAU) guidelines are: psychogenic, vasculogenic, neurogenic and hormonal. The EAU 2017 guidelines recommend measuring total testosterone (TS) level. This study is a meta-analysis of 14 randomised controlled trials based on the International Index for Erectile Function – Erectile Factor Domain (IIEF –EFD) before and after therapy. In TS less than 8 (231ng/dl) the score increased by 2.95 points. In TS less than 12 (346ng/dl) the score increased by 1.47 points. Several animal studies have demonstrated that TS regulates both nitric oxide and phosphodiesterase type 5 (PDE5) levels, both of which are essential for erectile function. In one trial, combined TS and sildenafil were more effective than monotherapy with sildenafil if TS levels were less than 400ng/dl. In mild ED, TS therapy may obviate the need for sildenafil. However, in moderate to severe ED, this may not be true as other factors will need to be considered such as diabetes and vascular disease.