Thomas Barwick/Getty By Jessica Hamzelou When is the menopause likely to happen? The average age that menopause occurs is 51, although symptoms can start several years before that. The age at which women experience the menopause is quite variable, and is partly influenced by genetics. So the age at which your mother went through the menopause will be a clue. Around 1 per cent of women can experience premature menopause, which occurs before the age of 40. How can you tell it is starting? The menopause itself is defined as beginning at the date of your final period, and is diagnosed a year after that happens. Symptoms can start three or four years beforehand, and can include hot flushes, night sweats, sleep loss, weight gain, mood swings, anxiety and problems with thought processing, as well as forgetfulness. For many women the first hint that they are entering “perimenopause”, as it is known, is erratic periods. There may be two or three months between each period, and they may be exceptionally heavy or light. How long do the symptoms last? This is also hugely variable between women. Some may not experience any symptoms at all, beyond their periods stopping. Others can have severe symptoms for years before and after the menopause – which can last for a decade or more. Is there anything you can do to prevent the onset of symptoms?