8 Surprising Things That Can Stop Your Pill from Working

Or make it less effective

The benefits and pitfalls of the Pill are extensively debated but, for many, it’s the best available form of contraception. Not only does it give you more control over when you get your period and, for some, lighten the flow and help to reduce pain, but it’s 99% effective at preventing unwanted pregnancy (but not STIs, so let’s also give a shout-out to condoms right about now).

The 99%, however, comes with a caveat. Even if you’re taking the Pill correctly, getting sick, taking other medication, or even just the place that you store your packets can have a major impact on its effectiveness.

We spoke to Karin O’Sullivan, clinical lead for sexual-health charity FPA, to get the lowdown on talking the Pill safely and reliably, without getting caught out.

The time of day

‘Taking the Pill at the same time each day will help you to remember to take it regularly,’ says O’Sullivan – and this is especially important if you’re taking the progestogen-only Pill.

‘If you’re taking the combined contraceptive pill, you’ve “missed a pill” if you take it more than 24 hours later than your chosen time. But if you’re taking the progestogen-only pill, you’ve missed one if you’ve taken it more than three hours after your chosen time (or 12 hours if your progestogen-only Pill has a type of progestogen called desogestrel).’ Missed the three-hour window? You’re no longer protected against pregnancy.

The stage of your cycle

‘For most pills, if you start them [begin taking for the first time] up to (and including) the fifth day of your period, you’ll be protected from pregnancy immediately,’ she continues.’But if you have a short menstrual cycle, with your period coming every 23 days or less, starting the Pill as late as the fifth day may not provide you with immediate contraceptive protection. This is because you may ovulate early in your menstrual cycle.

‘If you start the Pill at any other time in your cycle you’ll need to avoid sex or use additional contraception, such as condoms, for the first two days of pill-taking for progestogen-only Pills, seven days for most combined contraceptive Pills, or nine days for Qlaira.’ If you’re unsure, your doctor or nurse can provide advise about whether you need additional contraception.

Getting sick

Yep, because being stuck in the bathroom with a bug doesn’t suck enough by itself, it can also prevent the Pill from doing its job. ‘If you vomit within two hours of taking the Pill it won’t have been absorbed by your body, so just take another one as soon as you feel well enough and take your next Pill at your usual time,’ O’Sullivan advises. ‘As long as you’re not sick again, your contraception won’t have been affected.’

‘If you have very severe diarrhoea that continues for more than 24 hours, this may make the Pill less effective. If that happens, keep taking the Pill at the normal time, but treat each day that you have severe diarrhoea as if you had missed a pill. For the same reason, any conditions which cause diarrhoea, such as Crohn’s disease or irritable bowel syndrome, can also be a problem for your contraceptive cover if they’re not well controlled.’

Consuming laxatives

Remember a couple of years ago, when BooTea and other similar products came under fire for causing problems with the Pill? This is because many of these drinks have laxative effects and can stop your contraception from working. In fact, many of the brands even state this on their websites.

Of course, it’s not just diet teas – anything with laxative properties can prevent the Pill from getting properly absorbed into your system. So, if you’re taking them, you need to consider using additional contraception to ensure that you’re fully protected.

Undergoing gastric bypass surgery

The list of side-effects for gastric bypass surgery is extensive, and anyone undergoing the op should be fully informed of the risks. However, lots of people don’t realise that in addition to the potential risks of the procedure, it can influence your body’s reaction to your contraception.

‘If you’ve had gastric bypass surgery, this can permanently prevent the hormones from contraceptive pills being properly absorbed into your body,’ confirms O’Sullivan. ‘In this case, other methods like the implant, IUD or IUS might be a better contraceptive method for you.’

Taking other medication

‘The majority of medicines that can prevent the Pill from working properly are called enzyme-inducers,’ O’Sullivan says. ‘The hormones from the Pill enter your bloodstream through your liver, but because enzyme-inducers make everything go through your liver much more quickly, that can mean you absorb less of the hormones you need.’

Enzyme-inducers include medications for epilepsy, antiretroviral drugs for HIV, and complementary medicine St John’s Wort, which is used to treat mental-health conditions. It used to be thought that antibiotics would stop the Pill from working, but it’s now known that for most commonly prescribed tablets, this won’t be the case. There are only two very strong antibiotics which are generally only prescribed for TB or meningitis – Rifabutin and Rifampicin – that will have this effect.


‘If you fast for 24 hours at a time, and more than once in any month, there’s a risk this can prevent the Pill from working properly – so you should discuss it with your doctor or nurse,’ says O’Sullivan.

Again, this depends on the type of Pill you’re taking – with the combined contraceptive Pill, you can usually adjust the time you can take it so you take the Pill when you eat. But because the progestogen-only Pill has a shorter window in which you can take it, she says that you’ll have to combine this with an additional form of contraception. ‘If you regularly fast more than once a month, a different method of contraception might be more suitable for you,’ she adds.

Extreme temperatures


‘Keeping the Pill in very hot or cold temperatures can risk making them less effective,’ O’Sullivan says.

England may be the land of mediocre sunshine and disappointing snowfall, but it’s still worth bearing this in mind and keeping your pill packet out of the way of any possible extremes. And if you’re travelling to somewhere with a very hot or cold climate, you might want to discuss using another method with your doctor or nurse.

I’ve missed a pill – now what?

If you’re taking the progestogen-only Pill, and you’re more than three hours late in taking your next pill (12 hours if you are taking a desogestrel POP), you’re no longer protected against pregnancy. You should take a pill as soon as you remember, and then take your next one at the usual time. This may mean taking two pills in one day, but this isn’t harmful. For the next two days, you should also use an additional method of contraception, such as condoms, and if you’ve had unprotected sex during this time you should seek advice immediately because you might need emergency contraception.

If you’re taking the progestogen-only Pill, and you’re less than three hours late in taking your next pill (12 hours if you are taking a desogestrel POP), then you’re still protected from pregnancy. Just take a pill as soon as you remember, and take your next one at the usual time.

For those taking the combined contraceptive Pill, the impact of missing a pill is greater depending on how many you’ve missed, and whether it’s at the beginning of a new pack or not.

For example, missing one pill anywhere in your pack, or starting the new pack one day late shouldn’t be a problem. You’ll still be protected from pregnancy. But missing two or more pills, or starting the pack two or more days late, may affect your contraceptive cover. It’s more risky to start a pack late and miss more than one pill. This is because during the seven-day break, or placebo week, your ovaries aren’t getting any effects from the Pill. If you make the break or placebo week longer you may ovulate (release an egg).

If you’re not sure what to do, continue to take the Pill and use additional contraception such as condoms for the next seven days, or nine days for Qlaira. If you’ve had unprotected sex during this time you should seek advice immediately, as you might need emergency contraception.

This post was originally published on Cosmopolitan.com/uk.

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