Five things you didn't realise can mess with your contraceptive pill.

How good is birth control, you guys? Be honest, it’s pretty good.

It lets you decide when or if you want to get pregnant, keeps those pesky periods at bay by allowing you to skip a month, and just generally keeps women a lot safer sexually than the generations who came before us.

But like all good things in life, there are catches, especially for those using oral contraceptives like the pill.

According to Sydney-based GP Dr Dasha Fielder, the benefit of the Pill is that it’s been around for such a long time now, its variations are generally very effective and have an incredibly low failure rate. But there are still things women need to keep in mind.

1. Compliance

One of the most common things that can wreak havoc with the effectiveness of your birth control is compliance.

"The pill only works if you take it, and it only works well if you take it at approximately the same time of the day," Dr Fielder said.

"There are different types of pills on the market; different strengths and doses and completely different types of hormones within each different pill, so it really does depend on the type of pill you take as to how much leeway you've got with the timing around taking it, but ideally you need to take it at the same time and not miss it. Once you've missed it your entire cycle for that month is interrupted."

2. Drugs and alcohol

From the outside, having a big night out isn't something you'd link with your birth control, but depending on how you fare the next day, the two can correlate.

For starters, Dr. Fielder said, if you're hungover and vomiting, it's unlikely your pill will absorb, which can leave you susceptible to an unwanted pregnancy. And if you've gotten home late and slept all day, it's likely you'll be taking your pill late, which is another risk.

"The general message is that if you're not sure or you're worried, book an appointment with your doctor and discuss it that day, when the morning after pill can be offered, Dr. Fielder said, adding, "Don't wait longer than three days."

Listen: Mia Freedman talks all things contraception. Post continues... 

3. Vitamins

"Like anything else," Dr. Fielder said, "if women are taking anything else with the pill - even a vitamin - they need to check with their doctor or their pharmacist as to whether those two can be taken together."

She added, "there are certain vitamins that can interfere with the pill but it's something for a woman to speak to her doctor about."

4. Antibiotics

According to Dr. Fielder, "some antibiotics can interfere with the pill, but once again that's something a woman needs to discuss with her doctor; it's case by case."

So when the time calls, particularly around winter when chest and ear infections rise in likeliness, it's important to make sure you know of any interferences.

Dr. Fielder added, "most of the common antibiotics given now do not interfere with the pill but you must always discuss it case by case with your doctor to avoid pregnancy."

5. Sickness

From gastro to viruses - any illness that involves vomiting or diarrhoea is likely to put the effectiveness at your pill at risk. The reason, Dr. Fielder said, is absorption.

"If you're not well and can't absorb the pill, especially if you've some kind of gastrointestinal illness, then obviously, the pill may not be absorbed."

In those instances, Dr. Fielder said a good rule of thumb to follow is to ensure alternative forms of contraception (like condoms) are used for the first seven days after returning to taking your contraception as usual.