It can take a few months to experience the beneficial effects of testosterone, so why your GP has prescribed only one sachet is a mystery. It would be more usual to prescribe a box of Testogel, which contains 30 sachets. The label on mine says one sachet is to last 7-10 days, although I was told at the menopause clinic to aim for 14 days, so I apply a large pea-sized blob daily. It took about two months for me to notice any benefits. You will find plenty of info on here.
JP x