19M hairfall meds enquiry

so I visited a derma around 3 weeks ago as I was experiencing hairfall for 2 month she told me that it was just temporary shedding caused because I suddenly lost a significant amount of weight she gave me vit D, b12 and some meds of iron and other stuff and trilast hairserum and topisal 3% solution for scalp irritation. So what I want to know is how long does it take for these meds to show result as it's been 3 weeks and there isn't any change in the amount of hairfall