What is irregular bleeding?

A regular menstrual cycle usually means you’ll have 2–8 days of bleeding, called a period, every 21–35 days. If you get bleeding between your periods or outside this pattern, it’s called irregular bleeding.

There are 2 main types of irregular bleeding.

Irregular periods

Irregular periods are 2–8 days of bleeding in a row. Then a gap, another period, and another gap. As the gaps are different lengths, it’s hard to know when your next period will start.

This type of bleeding is often associated with irregular ovulation, which could be caused by PCOS (polycystic ovary syndrome).

Unpredictable bleeding

Unpredictable bleeding can be either bleeding often, like bleeding every day or bleeding rarely, such as bleeding a couple of days every 2–3 months. 

What causes irregular bleeding?

Irregular bleeding can have a wide range of causes. For example:

  • hormonal contraception

  • complications of pregnancy or abortion, including miscarriage, ectopic pregnancy, and incomplete abortion

  • medical conditions like polycystic ovary syndrome (PCOS), endometriosis and thyroid problems

  • STIs

  • cancer of the vagina, cervix or the lining of the uterus

Irregular periods can also happen because of:

  • puberty

  • the start of the menopause

  • extreme weight loss or weight gain

If you get irregular bleeding after you start a new method of contraception, it’s a good idea to wait for 3 months to see if it settles down.

If the bleeding stays irregular after that, look into other possible causes of the bleeding. So you can rule those out and be sure it’s caused by your contraception. 

What tests should you have?

To investigate the most common and treatable causes of irregular bleeding, it’s a good idea to:

  • do a pregnancy test

  • get tested for STIs (sexually transmitted infections) 

  • have a cervical screening (smear test) if you’re 25 or older

If you’ve done these and are still concerned about the bleeding, talk to your GP or sexual health clinic. They may want to do a speculum examination to check whether the bleeding is coming from the vagina or cervix.

If the cause of the bleeding isn’t found during the cervical test or examination, your health professional may suggest a pelvic ultrasound scan to check your womb, fallopian tubes, and ovaries.

How does contraception affect your bleeding?

The combined pill, the ring and the patch

These 3 contraceptives are combined methods, meaning they contain synthetic copies of the hormones oestrogen and progesterone.

With these methods, about 20% of people experience irregular bleeding in the first 3 months, but it usually settles after that.

If you’re using one of these combined methods without taking breaks, this is more likely to cause irregular bleeding.

Speak to your doctor if you’re using the pill, the patch or the ring and you experience:

  • irregular bleeding after the first 3 months

  • changes in your bleeding pattern after at least 3 months of use – for example, if you have had regular periods for months and then sudden unpredictable bleeding

  • pelvic pain or unusual vaginal discharge as well as the bleeding

Progestogen only contraception

It’s difficult to predict how your bleeding will be affected by progestogen only methods of contraception like the progestogen only pill, the implant and the injection., but here’s a guide to what other people have experienced:

The progestogen only pill containing desogestrel:

  • 5 in 10 people can expect to have no bleeding or infrequent bleeding

  • 4 in 10 people can expect to bleed or spot 3-5 times in 3 months

  • 1 in 10 people can expect to bleed or spot 6 times in 3 months

  • 2 in 10 people will get bleeding or spotting that lasts for 14 days (prolonged bleeding)

“The progestogen only pill has been brilliant – not had a period since I started 2 years ago. It is an extra benefit that I did not expect.”

Your periods can stop completely when you’re taking the progestogen only pill. This is an expected side effect of this method, and it’s not harmful. If you prefer to have a regular bleed, you might want to try another type of contraception.

The implant:

  • fewer than 1 in 4 people using the implant will have regular bleeds

  • infrequent bleeding is the most common bleeding pattern on the implant (around 1 in 3 people)

  • 1 in 5 people get no bleeding at all

  • 1 in 4 people have prolonged or frequent bleeding

“I tried out hormonal birth control, and the first time I had the implant it helped a lot by getting rid of most of my periods. However, the second time around I'm bleeding quite a bit.”

The injection

The injection stops periods completely in 70% of people. This happens by the end of the first year of use.

A small number of people, about 1 in 100, will get a lot of irregular, and sometimes heavy, bleeding.

“I love Depo. My period stopped immediately after the first shot. No dramatic mood swings. Don't have to worry about taking a pill every day.”

The hormonal coil

It’s common to get some irregular bleeding in the first few months after the hormonal coil is fitted. Different types of coil will affect your bleeding in different ways.

With the 52 milligram hormonal coil (Mirena), you’ll bleed less a year after fitting. Then most people have very infrequent bleeding. 24% have no bleeding at all.

With the 19.5 milligram coil (Kyleena), there’s a gradual reduction in bleeding, 23% of people with this coil will have no bleeding at all after 5 years.

With the 13.5 milligram hormonal coil (Jaydess), irregular bleeding is more common, but after a year, 13% have no bleeding at all.

Find out what to try if you're having irregular bleeding on progestogen only contraception

What type of contraception is best if you already have irregular bleeding?

If you are experiencing irregular bleeding and you’ve done a recent STI test to rule out infection, a pregnancy test to rule out pregnancy and you’re up-to-date with your cervical screening to rule out any other causes, you can use any type of contraception.

If you haven’t, your GP or health practitioner will want to look into possible causes of the bleeding before prescribing most methods. This is because once you’ve started a new contraception, it’ll be difficult to tell if the bleeding is caused by the contraceptive method or something else.

They’ll ask you:

  • when the problem started

  • what your bleeding pattern was before it became irregular or unpredictable

  • whether you have other symptoms with the bleeding, such as pain or vaginal discharge

  • if you have bleeding during or after sex

  • how heavy the bleeding is

  • whether you’re using contraception

  • if  you have been at risk of pregnancy

  • when you had your last normal period

  • if you’re taking any medications

  • what tests you’ve done to find the causes  

They’ll also want to know whether the bleeding is causing you harm – frequent heavy bleeding, for example, can cause anaemia. 

If you’re getting irregular vaginal bleeding, it’s usual to try to find the cause before you start a new method of contraception.

Reviewed by Helen Burkitt. Senior Sexual Health and Contraception Nurse
Last updated at: 14 March 2024
Published on: 15 November 2022