Is it normal to have menstruation twice in a month?

Not standard: Most women eventually establish a 28-day menstrual cycle with a 4-5 day bleed each month. Of course, there are those who have a 21-day cycle and those who have a 35-day cycle; so there is plenty of variability. If you are the unlucky 1/1000 gal with 2 periods a month, consider visiting with your fp to start birth control pills to control your periods to a more predictable monthly bleed.