A study by a team at the University of Southern California, Los Angeles (https://doi.org/10.5534/wjmh.190043) found no data for 67 of the 109 supplements on the market. Only 14 of the remaining 42 had consistent data on increasing blood testosterone. in my research, only four of them had small-group human clinical trial data. It was Eurycoma longifolia extract, Fenugreek extract, Magnesium, Shilajit.
Eurycoma longifolia extract (Tongkat ali extract) has undergone multiple clinical trials using Physta from Biotropics. Volunteers took 100 to 600 mg/day for 2 weeks to 3 months, but the results were mixed. Fenugreek extract has been clinically tested in women to improve perimenopausal discomfort and hormonal balance. The results of this clinical trial have been reported as paid papers, so the details are not known for me, but it is said that taking 250 mg twice a day for 46 days increased free testosterone by about 40% and improved symptoms.