• Restart/catch up with the pill cycle.
• When seven or fewer active COC pills have been missed, the woman should resume taking her pills as soon as possible.
• Restarting. If pills are missed in weeks 1, 2, or 3 of the pack: she should take the last missed pill as soon as possible and continue with the usual pill-taking schedule. Depending on when she remembers, she may take two pills at different times (the moment of remembering and her regular time), or two pills at the same time. For users of everyday COCs: if inactive pills are missed in week 4, she should throw away the missed inactive pills and continue the usual pill-taking schedule.
• Skipping the pill-free interval. If pills are missed in week 3 of the pack: she should finish the active pills in the current pack and then immediately start a new pack (omitting the pill-free interval or discarding any inactive tablets).
• When more than seven active COC pills have been missed, the woman needs to restart the COC as if she had not used it before.
• Assess if contraceptive protection has become unreliable.
• Loss of contraception is most likely if missed pills extend the pill-free (or inactive pill) interval to more than 7 days.
• The fpa (Family Planning Association) and the Faculty of Sexual and Reproductive Healthcare (FSRH), formerly the Faculty of Family Planning and Reproductive Healthcare (FFPRHC), regard contraception as becoming unreliable if:
• Two or more 20-microgram ethinylestradiol pills (Loestrin 20^®, Mercilon^®, Femodette^®) are missed — mnemonic: 'Two for twenty'.
• Three or more 30- or 35-microgram ethinylestradiol pills (all other COCs) are missed — mnemonic: 'Three for thirty'.
• The BNF (British National Formulary) regards:
• Contraception as unreliable if the delay is 24 hours or more (especially the first in the packet).
• Lost if more than 2 COC tablets are missed from the first 7 tablets in a packet.
• If contraceptive protection has become unreliable:
• Advise additional protection, such as condoms or abstinence, until the woman has taken her COC for 7 days in a row.
• Consider emergency contraception. If contraceptive protection has become unreliable and the woman has been sexually active without taking other precautions, consider the possibility of pregnancy and whether emergency contraception would be appropriate — see the CKS topic on Contraception - emergency.

• Recommendations by the fpa and FFPRHC on missed COC pills
• A 'missed pill' is a combined oral contraceptive (COC) pill that is completely omitted from being taken (i.e. 48 hours have elapsed since the last COC pill was taken). The term 'late pill' is no longer used [FFPRHC, 2005a; FFPRHC, 2007b].
• Consider providing information about missed pills when first providing or recommending the COC:
• The fpa (Family Planning Association) provides a useful leaflet with information for users of COCs — see www.fpa.org.uk.
• This information (in tables and in flowchart format) can be printed from guidance on Missed pills from the Faculty of Sexual and Reproductive Healthcare (FSRH), formerly the Faculty of Family Planning and Reproductive Healthcare (FFPRHC) [FFPRHC, 2005b].
• These missed pill rules do not apply if a woman has missed more than seven consecutive pills [FFPRHC, 2005b].

Experts agree on the need for clear, useful recommendations for managing missed pills, but they disagree on how to formulate recommendations for when missed pills would cause contraception to be lost. CKS has therefore summarized the two most common approaches, that by the fpa (Family Planning Association) and the Faculty of Sexual and Reproductive Healthcare (FSRH), (formerly the Faculty of Family Planning and Reproductive Healthcare [FFPRHC]), and that by the BNF (British National Formulary).

Missed COC pills: recommendations by the fpa and the FFPRHC.

• These 'missed pills rules' are recommended by the Faculty of Family Planning & Reproductive Health Care [FFPRHC, 2005a; FFPRHC, 2005b; FFPRHC, 2007b]. They are largely based on guidelines developed by a World Health Organization (WHO) expert working group [WHO, 2004a]. 
• Ovulation is a rare event after only 7 days of pill taking.
• After taking combined oral contraceptive (COC) pills on 7 consecutive days, at least 7 pills can be missed (such as occurs in the pill-free week) without the need for additional contraception or emergency contraception.
• Consequently, COC pills missed in weeks 2 (days 8–14) and 3 (days 15–21) of pill taking are unlikely to result in a loss of efficacy.
• The advice to use additional contraceptive protection (e.g. condoms) for the first 7 days after resuming the COC is precautionary in case further COC pills are missed.
• It is important to take an active (hormonal) pill as soon as possible when active pills have been missed.
• If COC pills are missed, the chance that pregnancy will occur depends not only on how many pills were missed, but also on when those pills were missed. On the basis of data regarding ovulation, the WHO expert working group determined that missing three or more active (hormonal) pills (or >= two pills for ethinylestradiol pills containing =< 20 micrograms) at any time during the cycle warrants additional precautions. The risk of pregnancy is greatest when active (hormonal) pills are missed at the beginning, or at the end, of the active pills (i.e. when the hormone-free interval is extended).
• Limited evidence on 20-microgram ethinylestradiol pills suggests that there may be a higher risk of pregnancy when these pills are missed than when 30-microgram ethinylestradiol pills are missed. Accordingly, the WHO expert working group recommended a more cautious approach when ethinylestradiol pills containing =< 20 micrograms are missed.
• Field experience from the first edition of the WHO guidelines Selected practice recommendations for contraceptive use highlighted the need for simple 'missed pill' recommendations.

Missed COC pills: recommendations by the BNF.

• The BNF does not explain how its recommendations were derived [BNF 53, 2007].