Thank you for your question. The combined oral contraceptive pill contains the female hormones estrogen and progesterone in a fixed dose. The combination works by preventing your ovary from releasing an egg. You need to take the pill daily for a consistent hormone level in your blood to stop your pituitary gland from stimulating your ovary. One effect of this is that your bleeding is reduced in quantity and duration. You will have only 7 days break between the end of one pack and the start of the next. You need to start your new packet on the exact 7 th day whether or not your bleeding has stopped or you risk getting pregnant in the subsequent cycle as the hormone levels may be insufficient to inhibit ovulation. The pill is very safe and its efficacy is unaffected by the duration or quantity of your bleed. There are no long term adverse effects of reduced bleeding and can actually be helpful in allowing you to build up your haemoglobin. Hope this helps. You can read more about the pill on www.patient.co.uk Best wishes