Vomiting or Diarrhea on the Pill: What to Do

You've taken your birth control pill, but a few hours later you're sick. Whether it's food poisoning, a stomach bug, or a reaction to medication, what does vomiting or diarrhea mean for your protection?

The short answer: it depends on how long after taking your pill you became ill, how long the illness lasts, and which pill you take. Here is what to check first.

Why Illness Can Affect the Pill

The birth control 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 diarrhea, 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: Check Your Pill Type and Instructions

Vomiting and diarrhea instructions vary by pill type, by specific product, and by which national guidance you follow. NHS guidance (UK) and CDC guidance (US) use different frameworks, and even within the UK, different combined pill brands use different windows. Always check the patient leaflet supplied with your specific pill.

UK NHS Guidance

Combined pills:

• Vomiting less than 3 hours after taking most combined pills may mean you need to take another pill.
• Qlaira and Zoely use a longer window of up to 4 hours.
• If vomiting continues, NHS guidance advises using backup contraception until you have taken pills for 7 days in a row without being sick.
• Diarrhea lasting more than 24 hours has separate instructions from a single episode.
• Always follow the patient leaflet supplied with your specific pill.

Traditional progestin-only pills: vomiting within 2 hours may affect absorption.

Desogestrel and drospirenone progestin-only pills:

• Vomiting within approximately 3 to 4 hours may affect absorption.
• The 12-hour window for desogestrel pills is the late-pill window, not the vomiting absorption window, these are different things.
• The 24-hour window for drospirenone pills is also a late-pill window, not the vomiting absorption window.

US CDC Guidance

Norethindrone and norgestrel progestin-only pills: CDC guidance addresses vomiting or diarrhea occurring within 3 hours of taking a pill. You may need to take another pill and use backup barrier protection temporarily, according to CDC guidance.

Combined birth control pills:

• CDC 2024 guidance differs from NHS guidance and uses a different framework.
• For vomiting or diarrhea occurring within 24 hours of a pill, or continuing for less than 48 hours, CDC guidance generally says redosing and additional protection are not necessary.
• If vomiting or diarrhea continues for 48 hours or longer, follow the CDC's extended-illness instructions and use barrier protection until you have taken 7 consecutive hormonal pills after recovery.

Opill (Over-the-Counter, US)

The FDA Opill label uses a 4-hour window for vomiting or severe diarrhea. If this happens within 4 hours of taking a pill, the label instructs you to use condoms or another barrier method for the following 48 hours. See our full guide on how to start and take Opill for the complete label instructions.

What Counts as Diarrhea on the Pill?

Not every bout of loose stools will affect your pill, and there is no single stool count that applies as a clinical threshold for every product or every guidance body. What matters more is how long the diarrhea continues and what your specific pill's instructions say.

• Short-lived diarrhea that resolves within a few hours is less likely to significantly affect absorption for most pills, but check your leaflet if you are unsure.
• NHS guidance treats diarrhea lasting more than 24 hours differently from a brief episode, and advises backup contraception until you have taken pills for 7 days without illness if it continues.
• CDC guidance for combined pills distinguishes illness lasting less than 48 hours, which generally does not require extra action, from illness lasting 48 hours or longer, which does.

See the pill-specific guidance above for the instructions that apply to your product.

What to Do If You're Ill

1. Identify your pill type and check your leaflet

   Different combined pills, progestin-only pills, and Opill each have different vomiting and diarrhea windows. See the pill-specific guidance above, or check the patient leaflet supplied with your product.

2. Assess the timing and duration

   How soon after your dose did vomiting occur, and how long has the illness continued? These factors determine whether your specific pill's instructions call for a replacement pill or backup contraception.

3. Take a replacement pill if your guidance calls for one

   If your pill-specific guidance says the dose may not have been absorbed, take a replacement as soon as you feel able to keep it down, then continue your pack as normal from the next scheduled pill.

4. Use backup contraception for the correct duration

   The duration varies by pill type and guidance, from 48 hours up to 7 days or more. See the pill-specific guidance above for the duration that applies to you.

5. If pills won't stay down

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

6. Contact a pharmacist or doctor if you're unsure

   If you've had unprotected sex during a possible at-risk period and are not sure whether your pill was absorbed, contact a pharmacist, doctor, OB-GYN, or sexual health service. This article cannot give you a definitive protection assessment for your individual situation.

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
• Celiac disease, untreated celiac disease can reduce absorption of many oral medications
• IBS with diarrhea-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 birth control options with your healthcare provider. A non-oral method such as the patch, vaginal ring, injection, implant, or IUD may provide more reliable protection.

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