What is the cause of a reduction in menstruation days. i used to menstruate full five days when i first started, it reduced to 4days and now 3days?

See your doctor: You describe symptoms that can only be honestly assessed by your doctor in his or her office. Only after a thorough evauation will he/she be able to come up with what's wrong and what to do to get you better.

Many causes: Most lilely u are not building up as much endometrial tissue which is fine, if you were my pt., i would do hormone blood testing and an exam and ultrasound, if everything is normal , it is totally fine yoru periods are less days, most women would be happy , nothing to worry about assuming the workup is normal.