How long does the pill take to work?

Dr Kathryn Basford

Medically reviewed by

Dr Kathryn Basford

Last reviewed: 29 May 2024

All contraceptive pills work to do the same thing, prevent pregnancy, but how long they take to work depends on the type of pill you’re taking and when in your cycle you start taking it.

The 2 types of contraceptive pills are the combined pill and the progesterone-only pill, also known as the ‘mini pill’. Here, we’ll take you through the different types of pills, how they work, and how long they take to be effective.

Somebody about to take the contraceptive pill

How long does it take for the pill to work?

How long the pill takes to work depends on which type of pill you take and which day in your menstrual cycle you start taking it. Other things can affect how long it takes too, such as if you have just given birth. You should seek advice from your nurse or doctor if you have a short or irregular menstrual cycle or if you’re not sure whether your pill is working.

Combined pill

If you start the combined pill on day 1 of your menstrual cycle (which is the first day of your period) up until day 5, it will work straight away. This means you are protected from pregnancy immediately.

If you start the combined pill after the 5th day of your menstrual cycle, it will take a week to work. You should use additional protection or avoid sex until you have taken the combined pill for 7 days in a row.

After giving birth:

You can usually start taking the combined pill 21 days after giving birth if you are not breastfeeding, but this can depend on other risk factors. It’ll start working straight away.

If you are breastfeeding, the combined pill can be started 6 weeks after giving birth. It will take 7 days for the pill to start working. It’s important to remember that the pill only protects you from pregnancy and not STIs, so you may still want to use a form of barrier contraception like condoms.

Mini pill

Starting the mini pill on days 1 to 5 of your menstrual cycle means it will start working straight away. However, if your menstrual cycle is shorter than 28 days, it can take 2 days for the mini pill to start working. You should use additional contraception or avoid sex until then.

If you take the mini pill after day 5 of your menstrual cycle, it will take 2 days to work.

After giving birth:

After having a baby, you can start the mini pill the day after birth up until day 21, and it will work straight away. If it has been longer than 21 days since giving birth, it will take 2 days for the mini pill to work.

from £14.00

from £19.00

from £24.00

No results found.

No results found.
Please check your spelling or try another treatment name.

Why aren't you always protected from the day you take the pill?

The pill works by changing your natural hormone levels to prevent ovulation (when a mature egg is released from your ovary). Depending on what day you take the pill, it may take a few days (usually 2 to 7) for the hormones to prevent ovulation, meaning you can still get pregnant.

How many days will I be protected after I take the pill?

You will be protected from pregnancy as long as you keep taking the pill every day and on time. If you use a combined pill and take a break between pill packs, you are still protected from pregnancy as long as you:

  • have taken your pills correctly
  • start your next tablet pack on the correct day

If you miss a pill, this can make it less effective, and you may not be entirely protected from pregnancy.

Am I still protected if I miss a pill?

Missing a pill or multiple pills will make it less effective, but you may still have some protection depending on the pill.

If you take the combined pill and miss:

  • 1 pill, or start 1 day late after your break, you will still be protected. If this happens, take the last pill as soon as you remember, even if you have to take 2 pills in a day.
  • more than 1 pill, it will become less effective. You should use another form of protection for 7 days and may need emergency contraception if you’ve had unprotected sex.

If you take the mini pill and miss:

  • a 3-hour mini pill but remember to take it within 3 hours of when you usually take it, you will still be protected.
  • a 12-hour pill, but remember to take it within 12 hours of your usual time, you will still be protected.

If you miss a mini pill later than 3 or 12 hours, you are not protected from pregnancy. Start taking your pill as soon as you remember and use another form of contraception for 2 days.

How effective is the pill at preventing pregnancy?

The pill is over 99% effective at preventing pregnancy when taken correctly. However, this is reduced by things like forgetting to take your pill or getting diarrhoea and vomiting after taking a pill.

When taken correctly, the pill is more effective than female diaphragms, which are between 92% and 96% effective when used correctly, and female condoms which are only 95% effective.

However, the pill is not effective at preventing sexually transmitted infections (STIs), so it’s best to use a condom when you have sex.

Can you get pregnant if you miss 1 pill?

This depends on which pill you are taking and how long it has been since it was due. You should still be protected from pregnancy if you only miss 1 combined pill, as long as you take it before your next dose is due.

When taking the mini pill, you will be protected as long as it is less than 3 or 12 hours since your last pill, depending on whether you take the 3 or 12-hour mini pill. If you aren’t sure, check your patient information leaflet or seek advice from your doctor.

Frequently asked questions

How long can I stay on the pill for?

You can use the contraceptive pill for as long as you need it. Your doctor will complete an annual checkup to make sure the pill remains a safe and suitable option.

Do I really need to take my pill at the same time each day?

Yes, it’s important to take your pill around the same time each day to ensure it remains over 99% effective. Set an alarm or reminder on your phone to help you remember, or put it beside your bed so you can take it every morning when you wake up.

Is there a risk of blood clots when using combined hormonal contraceptives?

When taking the combined pill, there is a very low risk of blood clots. You may be offered the mini pill if you have ever had a blood clot in a vein or if you have a family history of blood clots. Your doctor will make sure the contraceptive pill is suitable for you before prescribing it.

Am I still protected if I vomit after taking the contraceptive pill?

If you take the combined pill and vomit within 3 hours of taking it, you will need to take another dose to be protected. Take your pill straight away and then continue taking your pills again at your usual time. If you keep vomiting, use another form of contraception until you have taken the combined pill for 7 days without vomiting.

If you take the mini pill and vomit within 2 hours, take another pill straight away and then continue your pill at your usual time. If you vomit after this, use another form of contraception if you have sex, until you have taken your mini pill for 2 days without vomiting.

Will the contraceptive pill stop my period?

Taking the contraceptive pill can change your periods, including making them lighter and less frequent, or may stop them altogether. If you use the combined pill, speak to your doctor about taking your pill packets back to back, which means you won’t have a regular break. This is usually offered if you have painful or heavy periods or if you want to skip the break so you don’t have a bleed.

Are contraceptive pills safe?

The contraceptive pill has been designed to be a safe and effective way of preventing pregnancy. Your doctor will discuss your medical history and any other medications you take, so they can offer you the safest option.

Like any medication, there is a low risk of serious side effects. If you notice any side effects that worry you, speak to your doctor straight away.

Medically reviewed by:
Dr Kathryn Basford

Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with ZAVA. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.

Meet our doctors

Last reviewed: 29 May 2024

Don’t miss the latest advice from our doctors, and more. Sign up for our regular newsletter.
Sign up today

Contraceptive pills are a reliable way of reducing your risk of getting pregnant from sex. Asda Online Doctor by ZAVA offers most common brands of pill, so you can order your preferred brand by visiting our contraceptive pill service page.

(Reviews are for ZAVA UK)

ZAVA logo
gmc logo GPC logo

Authorised and regulated by