How Effective Is the Morning After Pill? Everything You Need to Know

What Is the Morning After Pill?

The morning after pill is a type of emergency contraception used to help prevent pregnancy after unprotected sex or contraceptive failure. It is designed for situations where there is a risk of pregnancy — not as a replacement for regular contraception.

There are two main types of emergency contraceptive pill available in the UK:

How Does Emergency Contraception Work?

Emergency contraception works primarily by delaying or preventing ovulation — the stage of the menstrual cycle when an egg is released from the ovary. If ovulation is delayed or prevented, sperm are unable to fertilise an egg, which reduces the chance of pregnancy occurring.

Many people are surprised to learn that the morning after pill does not affect an existing pregnancy. It does not:

Instead, it works before pregnancy occurs by interrupting the process that could lead to fertilisation.

How Effective Is the Morning After Pill?

Emergency contraception is highly effective when taken correctly and within the recommended timeframe. However, no emergency contraceptive method can guarantee that pregnancy will be prevented in every situation.

Research consistently shows that taking emergency contraception significantly reduces the likelihood of pregnancy compared with taking no action at all — which is why healthcare professionals recommend seeking treatment as soon as possible.

Does Timing Affect Effectiveness?

Timing is one of the most important factors affecting how well emergency contraception works. The sooner treatment is taken, the greater the likelihood that ovulation can be delayed or prevented.

Although some emergency contraceptive pills can be taken several days after unprotected sex, effectiveness generally decreases as more time passes — because ovulation becomes increasingly likely to occur. We always recommend seeking advice as quickly as possible if you think emergency contraception may be needed.

What If I’ve Already Ovulated?

Because the morning after pill works mainly by delaying ovulation, it may be less effective if ovulation has already taken place. Once an egg has been released, preventing fertilisation becomes more difficult. One challenge is that many people are unsure exactly when they ovulate, particularly if their menstrual cycle varies from month to month.

If there is concern that ovulation may already have occurred, alternative forms of emergency contraception may be discussed. For some individuals, a copper intrauterine device (IUD) may be an option because it can remain effective even after ovulation. This is one reason why seeking professional advice promptly is important.

What Should I Do If I Vomit After Taking It?

For emergency contraception to work properly, the medication must be absorbed by the body. If you vomit shortly after taking the morning after pill, there is a possibility that the medicine may not have been fully absorbed — and it is important to seek advice as soon as possible.

• Further assessment
• A replacement dose
• Advice on alternative options

The exact recommendations vary depending on which emergency contraceptive pill you have taken and how long after taking it the vomiting occurred. Our pharmacy team can provide guidance on the most appropriate next steps.

When Should I Take a Pregnancy Test?

Although emergency contraception is effective, there is still a small possibility of pregnancy. It is important to remain aware of any changes to your menstrual cycle afterwards.

• Your period is late
• Your next period is unusually light or heavy
• You experience symptoms that could suggest pregnancy
• It has been three weeks since the unprotected sex occurred

Modern home pregnancy tests are highly accurate when used correctly. If you receive a positive result or have ongoing concerns, further medical advice should be sought.

Where Can I Get Emergency Contraception?

Emergency contraception is available from a number of healthcare providers throughout the UK. Many NHS services provide emergency contraception free of charge, although availability can vary depending on your local area.

• Community pharmacies
• NHS sexual health clinics
• Some GP surgeries
• NHS walk-in centres
• Community contraception services

At our pharmacy, we provide confidential advice and can help determine the most appropriate emergency contraception option based on your individual circumstances. If you have had unprotected sex or experienced a contraceptive failure, do not delay seeking advice — the sooner emergency contraception is taken, the more effective it is likely to be.