Some women find their menstrual cycle isn't always regular. Their periods may be early or late, and may vary in how long they last or how heavy they are each time.
Your normal menstrual cycle can be disturbed if you change your method of contraception , or if you have an imbalance of the reproductive hormones oestrogen and progesterone.
Many factors can cause a hormone imbalance, from polycystic ovary syndrome (PCOS) to extreme weight loss and excessive exercise.
However, you shouldsee your GPif:
You may need a different contraceptive, or further investigations may be needed to find out whether you have an underlying health condition.
After puberty, most women develop a regular menstrual cycle, with around the samelength of time between periods.
Menstrual bleeding usually lasts two to seven days, with the average beingfive days.
Find out what causes irregular periods, when to see your GP and how irregular periods can be treated.
Read more about the possible causes of irregular periods, including lifestyle factors, contraceptives, polycystic ovary syndrome and gynaecological problems.
Treatment for irregular periods isn't always necessary. However, you should see your GP if you have changes to your periods, such as bleeding or spotting between periods or after sex.