** Thanks for contacting with your health concern 1. when vitamin or multivitamin supplements are taken in recommended dietary allowance, they will not alter menstrual cycle, however, overdosing can cause changes in the hormones which can affect the menstrual cycle. PS. although cause could be something else, consult your physician to seek suggestion to know why you have missed your periods, a Gynecologist would be ideal to consult, for appropriate examination/investigations, like . UPT [urine pregnancy test] - low thyroid [hypothyroidism]or having a high level of prolactin [hormone] can also cause the same. - excessive stress/worry [present] - suffering from PCOD [polycystic ovarian disease]