The 'low-dose step-up' protocol is the most suitable method to establish an appropriate FSH threshold, which involves a starting FSH dose of 75 IU/day given for 7 to 14 days. Subsequent dose increments of 37.5 IU/day at weekly intervals is determined based on the ovarian response, usually when a follicle of diameter ≥10 mm is not seen in the ovaries. Human chorionic gonadotrophin (hCG) is then injected when the leading follicle is ≥18 mm in diameter.