I started taking black cohosh for my hot flashes a few days ago when should i expect its effect

Hard to tell.: Supplements like cohash, soy, chasteberry have estrogen like activity but they are not estrogen and are less likely to help with some of the stronger hot flashes that women have as they transition thru menopause. Some women do find them helpful but many do not. I would think if your are going to see improvement you would see within the first several weeks. Generally felt to be a safe product.