Everything you need to know about the pill

The birth control pill has been one of the most popular forms of contraception for decades, and it's easy to see why. It's effective, convenient, and for some people, it can offer benefits beyond preventing pregnancy, like lighter periods or clearer skin.

But if you're thinking about starting the pill, switching pills, or just want to understand how it works, you probably have questions. What's the difference between the combined pill and the mini pill? How effective is it? What happens if you miss one?

With the help of Dr. Jennifer Boyle, obstetrician and gynecologist at Massachusetts General Hospital, Massachusetts, US, here's what you need to know before choosing the pill.

Key takeaways

• There are two main types of birth control pills: combined oral contraceptive pills (COCs) and progestin-only pills (POPs).
• The pill works best when taken at the same time every day. Perfect use makes it over 99% effective, while typical use, taking into consideration missing a pill from time to time, is around 93% effective.
• Deciding whether the pill is right for you depends on your health, lifestyle, and preferences. Your doctor can help you choose the best option for you.
• Like any medication, the pill can cause side effects. Some of these can improve after the first few months of use, but it’s good to be aware of them. 

What is the birth control pill?

The pill is a type of hormonal contraception that you take once a day to help prevent pregnancy.

There are two different types:

• Combined oral contraceptive pills (COCs): These contain both estrogen and progestin (a synthetic version of progesterone).
• Progestin-only pills (POPs): Also known as the mini pill, these contain only progestin.

Although both are designed to prevent pregnancy, they aren't identical.

How does the pill work?

Ready for a quick science lesson?

To become pregnant, one of your ovaries has to release an egg each cycle during ovulation. Hormonal birth control changes the hormone signals involved in this process, making pregnancy much less likely.

Combined pills primarily work by:

• preventing ovulation
• thickening cervical mucus, making it harder for sperm to reach an egg
• thinning the lining of the uterus

Progestin-only pills also thicken cervical mucus and thin the uterine lining. 

"The extra progestin makes the cervical mucus thicker, making it harder for sperm to travel into the uterus," says Dr. Boyle. This makes it harder for conception to happen. 

How effective is the pill?

When taken exactly as directed, both types of pill are more than 99% effective at preventing pregnancy.

In real life, though, remembering to take a pill every day isn't always easy. Because missing your pill can happen, the pill is considered about 93% effective with typical use.

Taking your pill at roughly the same time every day helps keep it working as intended. Setting an alarm on your phone might act as a helpful reminder. Keeping it by your bed may also prompt you to take it either first thing in the morning or before you go to sleep. 

Combined pill vs. mini pill: What's the difference?

Both pills prevent pregnancy, but one may suit you better depending on your medical history and lifestyle.

Combined pill (COC)

The combined pill contains estrogen and progestin. It may be a good option if you're looking for:

• reliable pregnancy prevention
• lighter, more predictable periods
• less menstrual cramping
• possible improvements in acne

However, because it contains estrogen, it isn't suitable for everyone. Your doctor may recommend avoiding combined pills if you have certain medical conditions, like high blood pressure, or have a history of blood clots, stroke, or certain types of migraine, and they may recommend you don’t take it if you are over 35 and a heavy smoker. 

Progestin-only pill (POP)

The mini pill contains only progestin, making it a good option for people who can't or prefer not to take estrogen. It can be suitable if you're:

• breastfeeding
• advised to avoid estrogen for medical reasons (see above)
• looking for an estrogen-free option

Before you start taking a new type of contraception, it’s always a good idea to speak to your doctor. They’ll be able to help you weigh up your options and work out what might be best for you. 

What are the benefits of the pill?

Preventing pregnancy is the main reason many people choose the pill, but it can have other benefits too.

Depending on the type you're taking, the pill may help:

• make your periods lighter
• reduce painful cramps
• improve acne
• ease symptoms of PMS

Everyone’s bodies are different, and you might experience some of these benefits or not notice any. This is totally normal. 

What side effects can the pill cause?

Like any medication, the pill can cause side effects. Some of the most common include:

• nausea
• headaches
• breast tenderness
• spotting or irregular bleeding
• changes to your periods

In some women, hormonal contraceptives can lead to negative changes in their mood or a dip in their sex drive while taking the pill. This is rare, but if it occurs, it is important to tell your doctor to find a solution

These might improve within two or three months. If side effects are severe or don't settle, speak to your doctor. Sometimes switching to a different pill might resolve them. Choosing the right birth control method can involve a little trial and error because everyone responds differently to hormones, as we’re all different. 

What should you do if you forget to take your pill? 

You might have gone to stay with a friend and forgotten to pack your pills, or be traveling, and the change in your routine means you miss the time you’d usually take it. Forgetting a pill now and then can happen. What you should do next depends on which type of pill you're taking and how late you are.

If you're taking the combined pill

The combined pill is a little more forgiving if you miss one.

• If you're less than 24 hours late (or you've missed one pill): Take it as soon as you remember, even if that means taking two pills in one day. Keep taking the rest of your pack as normal. 
• If you've missed two or more pills (or you're more than 48 hours late): Take the most recent missed pill as soon as you remember and continue taking the rest of your pack as normal. Use condoms or avoid sex for the next seven days while the pill becomes fully effective again.

If you missed pills during the first week of your pack and had unprotected sex in the previous seven days, you may also need emergency contraception. Speak to your doctor as soon as possible for advice.

If you're taking the progestin-only pill (mini pill)

The mini pill is more sensitive to timing than the combined pill. How late is "too late" depends on the type of mini pill you've been prescribed. Some have a 3-hour window, while others have a 12-hour window. If you're unsure, check the patient information leaflet or ask your doctor.

• If you're still within your pill's time window: Take the pill as soon as you remember and continue taking the rest as usual. You should still be protected from pregnancy.
• If you're outside your pill's time window: Take one pill as soon as you remember, then continue taking the rest at your usual time (this may mean taking two pills on the same day). You'll need to use condoms or avoid sex for the next two days while the pill becomes fully effective again.

If you've had unprotected sex after missing your pill and before you've been taking it reliably again for two days, you may need emergency contraception. A doctor can advise you on the best option.

If you're ever unsure whether you're protected, don't guess. Check the instructions that came with your pill and speak to your doctor. They'll be able to explain exactly what to do based on the type of pill you're taking and how many pills you've missed.

How do you choose the right pill?

There's no single "best" birth control pill. The right choice depends on your medical history, whether estrogen is safe for you, your lifestyle, and what you're hoping to get from contraception.

"First, make sure there are no medical reasons to choose one method over another," says Dr. Boyle. "After that, it's mainly about personal preference." If you're unsure where to start, your doctor can talk through your options and help you find the pill that best fits your needs.