Can the morning after pill affect your period?

Yes, the morning after pill can delay your period. It will usually only delay your period by a few days.

You might not be pregnant if your period is slightly late, but it’s understandable if this concerns you. If you still have not had your period after 7 days from when you expect to get it, you should take a pregnancy test.

Other factors can change when your period comes too. For example, your period might be delayed if you:

• normally have irregular cycles
• are stressed
• take other medications
• have recently taken other forms of birth control
• have lost weight recently
• have certain health conditions like thyroid disorders, diabetes, or polycystic ovarian syndrome (PCOS)

Here is a more detailed overview of factors that can delay your period:

If you take the morning after pill shortly after having unprotected sex (within 24 hours), it is usually very effective. It should prevent unwanted pregnancies for over 95 to 99% of women.

“It’s very common to have a late period with the morning after pill, and both Levonelle and ellaOne can delay periods. A few days of not knowing can undoubtedly be very worrying as you wait for your period to come. However, remember that, if taken correctly, emergency contraceptive pills are typically highly effective. The most likely explanation is simply that the emergency contraceptive pill has delayed your period for a few days.” – Dr Brenda Ikeji, Medical Editor.

Your period can be up to a week late after taking the morning after pill. In some cases, it can be even more than a week. This may depend on the contraceptive used. For example, in one clinical study involving 232 women who took the emergency contraceptive Levonelle:

• 17% found that their period came 2 to 4 days late
• 7% found that their period came over 4 days late

On the other hand, clinical research into ulipristal 30mg (ellaOne) found that:

• 18.5% of women had their period more than 7 days late
• 4% of women had their period more than 20 days late

So, if your period is later after the morning after pill, this does not necessarily mean you’re pregnant.

The morning after pill can affect your period because it prevents ovulation. Ovulation occurs when your ovaries release an egg to get ready for fertilisation by sperm. Ovulation is a stage that normally happens around the middle of your menstrual cycle.

Your menstrual cycle is made up of 4 main stages:

• menstruation
• the follicular phase
• ovulation
• the luteal phase

If the morning after pill affects 1 stage of the cycle, it can impact a later phase too.

Emergency contraceptive pills contain active ingredients that can temporarily delay or prevent ovulation, resulting in delays or changes to menstruation.

In addition to making your period late, the morning after pill can also make your period come early, as well as causing heavier bleeding, lighter bleeding, or spotting.

Disruption to your menstrual cycle is a common side effect of the morning after pill, and is usually temporary. Your period should go back to normal in the following cycle.

Can ellaOne delay your period?

Yes, your period can be delayed by up to 7 days when taking ellaOne, according to the manufacturer. ellaOne contains ulipristal acetate, an ingredient that binds to progesterone receptors in the body to delay or prevent ovulation, which can sometimes cause a delay in menstruation later in your cycle.

Can Levonelle delay your period?

Yes, like ellaOne, Levonelle can delay your period by up to 7 days, or sometimes even more. Levonelle contains the active ingredient levonorgestrel, a type of progestin. Progestins are synthetic hormones that mimic the natural hormone progesterone. Levonorgestrel works in the body to delay or prevent

ovulation, and as a result, can cause a disruption or delay in menstruation.

Yes, both Levonelle and ellaOne can cause your period to arrive early. A study on levonorgestrel (Levonelle) found that 21% of women reported that their periods came 2 to 4 days earlier than usual.

A clinical trial on ulipristal acetate (ellaOne) also reported that 7% of women experienced their periods as early as 7 days before they were expecting it.

These effects can vary from person to person and may also be impacted by other factors such as personal health or stress. If you’re concerned about an early period while taking the morning after pill, contact your doctor.

The only way to know if emergency contraception has worked is when you get your next period. Unfortunately, this does mean you have to wait to know for sure whether you’re pregnant or not.

If you’ve taken the morning after pill as soon as possible, within 24 hours of unprotected sex, there’s a 95 to 99% chance that it has worked. The later you take the Levonelle morning after pill, the less effective it becomes at preventing pregnancy, though ellaOne remains effective throughout the whole 5 days it can be taken. Levonelle (levonorgestrel) can work up to 72 hours, and ellaOne up to 120 hours after unprotected sex.

➤ For more information about emergency contraception success rates and timelines, see our guide to the effectiveness of the morning after pill.