Vomiting or Diarrhoea on the Pill: Are You Still Protected?

You've taken your pill for the evening, but a few hours later you're unwell. Whether it's food poisoning, a stomach bug, or a reaction to medication, what does being sick mean for your contraceptive cover?

This is a question that comes up frequently, and the answer matters. Here's what you need to know.

Why Illness Can Affect the Pill

The contraceptive pill works by being absorbed through your gastrointestinal tract. Hormones pass from the tablet, through your stomach and intestinal lining, into your bloodstream. If this process is disrupted, by vomiting or severe diarrhoea, the hormones may not reach your bloodstream at adequate levels.

This is different from a drug interaction. It's a practical, physical issue: if the pill doesn't stay in your body long enough to absorb, it can't do its job.

Vomiting: The 2-Hour Rule

This 2-hour rule applies to both combined and progestogen-only pills. However, because the mini-pill already has a shorter protection window, any illness-related disruption should be treated with extra caution. If you're on a mini-pill and you vomit within 2 hours of taking it, take a replacement pill and use condoms for 48 hours.

Diarrhoea: When Does It Count?

Not every bout of loose stools will affect your pill, but severe or prolonged diarrhoea can.

• Severe diarrhoea, 3 or more watery stools within 24 hours, is defined as clinically significant. At this level, intestinal transit is fast enough that the pill may not be adequately absorbed. Treat it as a missed pill.
• Short-lived diarrhoea (one or two loose stools that resolve quickly) is unlikely to significantly affect absorption. You are probably still protected.
• Prolonged diarrhoea lasting more than 24 hours should also be treated as a missed pill. Use backup contraception while unwell and continue for 7 days after recovery (combined pill) or 48 hours (mini-pill).

What to Do If You're Ill

1. Assess the timing

   Did you vomit within 2 hours of taking your pill? Is your diarrhoea severe, 3 or more watery stools in 24 hours? If neither applies, you are likely still protected.

2. Take a replacement pill

   As soon as you feel well enough to keep it down, take a replacement pill. Then continue your pack as normal from the next scheduled pill.

3. Use backup contraception

   Use condoms for the duration of the illness and for 7 days afterwards (combined pill) or 48 hours (mini-pill).

4. If pills won't stay down

   If vomiting is so severe that you cannot keep any pills down for more than 2 days, contact your GP or sexual health clinic. They may recommend emergency contraception or a temporary alternative method.

5. Consider emergency contraception

   If you've had unprotected sex during the at-risk period, and your pill may not have been absorbed, consider emergency contraception as soon as possible.

Conditions That May Chronically Affect Absorption

Some women have ongoing digestive conditions that affect how consistently their body absorbs oral medication:

• Crohn's disease and ulcerative colitis, inflammation and rapid intestinal transit can impair pill absorption
• Coeliac disease, untreated coeliac disease can reduce absorption of many oral medications
• IBS with diarrhoea-predominant symptoms, chronic loose stools can affect how reliably the pill is absorbed
• Bariatric surgery, some procedures alter intestinal anatomy and can significantly affect drug absorption

If you have any of these conditions, it's worth discussing your contraceptive choice with your GP. A non-oral method such as the patch, vaginal ring, injection, implant, or IUD may provide more reliable protection.

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