Tongkat ali (Eurycoma longifolia) is a traditional Southeast Asian herbal remedy historically used to enhance male virility and vitality. In recent decades, it has garnered scientific interest for its potential to support healthy testosterone levels. Several human and animal studies have investigated tongkat ali's effects on testosterone and related parameters. A number of randomized controlled trials (RCTs) and observational studies suggest that supplementation with tongkat ali extract can increase total and free testosterone levels, particularly in men with low baseline testosterone or those experiencing stress-related reductions. Proposed mechanisms include stimulation of luteinizing hormone and reduction of sex hormone-binding globulin, thereby increasing bioavailable testosterone. Additionally, some studies report improvements in sexual function, muscle strength, and mood, which may be mediated by changes in testosterone.

However, the body of scientific evidence is still limited by small sample sizes, short study durations, and variable extract standardization. Meta-analyses and systematic reviews acknowledge a positive trend but emphasize the need for larger, high-quality trials to confirm efficacy and safety over the long term. Thus, while tongkat ali's use for testosterone support is rooted in both tradition and emerging scientific validation, the current evidence base is moderate rather than definitive.