The average age to begin menopause is 51, according to WebMD. The exact age when each woman enters menopause is thought to be widely determined by genes. When it occurs before the age of 40, it is considered premature menopause.
Menopause is preceded by the perimenopause stage, which starts at about the age of 47 when menstrual cycles become irregular. Menopause that comes about as a result of illness, treatment or surgery is known as premature ovarian failure or induced menopause, notes WebMD.
Common menopausal symptoms are mood swings, lower sex drive, hot flashes, sweating and headaches. Other symptoms include painful sex, vaginal dryness, a racing heart and sleep problems, states WebMD. Vaginal bleeding is deemed abnormal after menstrual periods have ceased for more than a year.