There are two main types of pill which vary in hormone content and the way they work. The most widely used are the combined pills which have two hormones, oestrogen and progestogen. There are also pills which have progestogen only and no oestrogen. This pill is suitable for women who cannot tolerate oestrogen.
This fact sheet is about the progestogen-only pill:
Progestogen-Only Pill.pdf 59.17 kB