 [ Symptoms ] i am 16 my period cycle is 55 days is it normal [ Disease ] hi… first of all you have to make a record of your periods start and end date for better monitoring about it… normally periods takes 21 35 days if they are regularly irregular then you should see a doctor for some check she may need to do us to your ovaries and uterus to check for polycystic ovarian syndrome or any other abnormality… regards