Starting combined oral contraceptives
Combined oral contraceptives (COCs) can be started at any stage of the menstrual cycle, except for formulations containing cyproterone; see Quick Start. If early pregnancy cannot be excluded, a pregnancy test is recommended 4 weeks after starting, or 3 weeks after starting if no further episodes of unprotected sex occurred in the first week of use. For general advice about excluding pregnancy, see Starting intrauterine contraception.
Provided an active (hormone) pill is taken from the start, COCs are immediately effective if:
- started on day 1 to 5 of a regular menstrual cycle
- started less than 21 days postpartum
- started within 5 days of an abortion
- switching between combined oral contraceptive formulations or the vaginal ring; begin the new pill packet on a hormone pill or insert the vaginal ring at any time but no longer than 24 hours after the end of the hormone-free interval
- switching from an etonogestrel implant or depot medroxyprogesterone injection
- switching from a copper IUD during days 1 to 5 of a regular menstrual cycle.
COCs take 7 days to work at all other times, and if the current method of contraception is not effective at the time of switching (eg late doses, injection or replacement)1. For more information about time to effectiveness when switching between contraceptive methods, see printable table.
Most COC regimens involve 21 days of active (hormone) pill use, followed by 7 days of inactive pill use (hormone-free interval), during which a withdrawal bleed usually occurs.
Use:
Advise users:
- which pill to start on, and the difference between active and inactive pills
- what to do if a pill is missed
- that poor absorption or some drug interactions can reduce the effectiveness of the COC, requiring use of an additional method of contraception.