Combined oral contraceptive pills are a type of oral medication that is designed to be taken every day, at the same time of day, in order to prevent pregnancy. There are many different formulations or brands, but the average pack is designed to be taken over a 28-day period, or cycle. For the first 21 days of the cycle, users take a daily pill that contains hormones (estrogen and progestogen). The last 7 days of the cycle are hormone free days. Some packets only contain 21 pills and users are then advised to take no pills for the following week. Other packets contain 7 additional placebo pills, or biologically inactive pills. Some newer formulations have 24 days of active hormone pills, followed by 4 days of placebo (examples include Yaz 28 and Loestrin 24 Fe) or even 84 days of active hormone pills, followed by 7 days of placebo pills (Seasonale). A woman on the pill will have a withdrawal bleed sometime during her placebo pill or no pill days, and is still protected from pregnancy during this time. Then after 28 days, or 91 days depending on which type a person is using, users start a new pack and a new cycle.