Bleeding between periods, also known as spotting or intermenstrual bleeding, can occur for a number of reasons. In some cases, it may be down to starting a new form of hormonal contraception, or missing a pill.

However, if you do notice any abnormal vaginal bleeding, are concerned by it, or are unsure of the cause, you should speak to your GP.

In the majority of cases it is not likely to be anything serious, but sometimes it may be indicative of a problem requiring medical attention.

Here, we’ll discuss:

  • what is considered to be abnormal
  • some of the reasons why abnormal bleeding occurs
  • and what will happen when you visit your doctor

What is abnormal vaginal bleeding?

Because no two people are the same, there is no set definition of ‘normal’ or ‘abnormal’.

Really, abnormal vaginal bleeding is anything that is unusual for you.

Abnormal menstrual bleeding might occur:

  • when you are not expecting your period
  • during pregnancy
  • after the menopause

Menstrual bleeding might also be considered ‘abnormal’ if it is heavier or lighter than usual.

When should I see a doctor?

If you experience any abnormal bleeding, it is advisable to report it to your doctor. 

Intermenstrual bleeding can occur for numerous different reasons. In many cases, where it occurs unaccompanied by other symptoms, the cause may be benign; and abnormal bleeding may pass without the need for treatment.

However, there are some instances where medical attention may be required.

This includes:

  • if bleeding is persistent, lasting for more than a week
  • if bleeding is severe or excessively heavy
  • if you are pregnant (or think you might be pregnant)
  • if bleeding is causing you to feel lightheaded
  • if bleeding happens during or after sex
  • or if other symptoms are also present, such as abdominal or pelvic pain, or a fever.

What causes bleeding between periods?

Abnormal bleeding can often be the result of hormonal changes or fluctuations in the body.

Less often, a physical injury, infection or illness might be the cause.

Here, we’ll examine some of the different causes, and when you should seek medical advice.

Contraception

  • Starting hormonal birth control

Many women who use hormonal contraceptives (such as the combined or minipill, or the contraceptive patch) may experience bleeding or spotting between periods during the first three months after starting it.

However, you should tell your doctor if bleeding becomes a problem, or persists beyond this.

  • Missing a pill

Intermenstrual bleeding may also occur due to a missed pill (or patch).

If someone taking oral birth control becomes ill, and develops vomiting or diarrhoea as a result, this can sometimes mean that the pill is not absorbed into the body (for instance, if someone is sick within two hours of taking the pill, or if someone passes watery bowel movements for 24 hours after taking it).

In such cases, this may count as a missed pill and also cause irregular bleeding.

(If you’ve missed a dose of your regular hormonal contraceptive, or become ill while taking it and need guidance on what to do, speak to your doctor.)

  • Missing a pill-free week

Women who carry on taking their pill throughout their usual pill-free week (or days) are also likely to disrupt or delay their regular period, and this can result in spotting or bleeding at irregular times during the following weeks.

  • Taking the morning after pill

Emergency contraception, or the morning after pill, can cause irregular bleeding when it is taken. This should only last for a few days, but in some cases may continue up until the next time the person who has taken it is due to have their period.

Once again, if bleeding persists or becomes very heavy, you should speak to your GP.

Stress

Cortisol, which is released in larger amounts when we go through periods of stress, can interfere with the function of reproductive hormones, and result in changes to the normal menstrual cycle.

While it’s common for people to experience stress to some extent if they have a demanding job or keep a busy schedule, you should take steps to try and manage it if you feel perpetually stressed, are experiencing physical symptoms as a result of it, or think it could be affecting your overall health.

Perimenopause

Prior to the menopause, during what is known as the perimenopause, periods can become irregular due to hormonal changes taking place.

For the majority of women, the menopause occurs between the ages of 45 and 55, with 51 being the average age of onset. But it can occur earlier in some women. When it develops before the age of 40, this is referred to as premature menopause, or POI (premature ovarian insufficiency).

Postmenopausal women who experience vaginal bleeding should talk to their GP, as this may be an indicator of an illness requiring medical advice.

Other causes

Less commonly, irregular bleeding can be caused by:

  • Vaginal dryness

This can cause the inside of the vagina to become irritated, and more prone to bleeding during and after sex.

  • Trauma or injury

If someone’s vagina becomes injured during sex, this can result in bleeding. The tissues in the vagina and cervix contain a lot of blood vessels, and will tend to bleed more than a typical wound.

  • Infection

Some types of infections, such as pelvic inflammatory disease and STIs like gonorrhoea and chlamydia, can cause bleeding to occur at abnormal times, or during intercourse.

In some cases, but not all, other symptoms (such as unusual discharge or urethral pain) may be present too.

If you have recently had sex with a new partner and you notice unusual vaginal bleeding, you should see your GP or make an appointment with a GUM clinic as soon as possible.

  • Cervical ectropion (or cervical ‘erosion’)

This is when the line separating fragile cervical cells (glandular cells) and womb cells ‘erodes’ (or rather, becomes less clearly defined), and glandular cells develop on the outer part of the cervix. This can cause the area to become raw, and lead to bleeding between periods, or during and after sex.  

It is not known exactly why it occurs, but hormonal changes are suspected to be a factor.

  • Fibroid and polyps

These are different types of growths which can develop in the uterus, and might cause bleeding. Fibroids can be small or large and are made up of muscle tissue; whereas polyps are fairly small, usually round or oval and are made up of endometrial tissue.

  • Endometrial hyperplasia

This is where the lining of the womb becomes thick, and this can result from changes in oestrogen and progesterone levels in the body. This then results in unusual uterine bleeding; someone’s period might be heavier than normal, or their period may last longer.

  • Problems during pregnancy

See your GP right away if you experience vaginal bleeding of any type during pregnancy.

  • Cervical or endometrial cancer

These conditions don’t generally cause symptoms which are obvious during their earlier stages, but abnormal vaginal bleeding can be an early sign.

In the majority of cases, someone with abnormal vaginal bleeding will not have cancer. However, it is important to see your doctor if you notice it.

For women aged between 25 and 64, attending regular cervical screening (smear tests) can help to detect signs of cervical cancer at an early stage, and enable treatment to be started. They should be carried out every three years in women aged between 25 and 49, and every 5 years in women aged between 50 and 64.

  • Abortion procedure

Vaginal bleeding is common following a termination procedure, and may last for up to a fortnight. However, if bleeding persists beyond this time, you should see a doctor.

What will happen when I visit my doctor?

They will typically ask you questions about your symptoms, and might refer you to a gynaecologist or arrange some investigations to help them determine a diagnosis.

Investigations that might be carried out due to intermenstrual bleeding include:

  • STI tests. These could be taken in the form of a vaginal swab.
  • A pregnancy test.
  • Physical examination. The doctor may wish to carry out an internal examination. An instrument called a speculum is sometimes used to obtain a view of the cervix.
  • Blood tests. These can check for abnormal hormone levels.
  • Ultrasound scans. Transabdominal and transvaginal ultrasound scans can be used to check for anatomical abnormalities.
  • Cervical screening or smear test. As mentioned earlier, this test is regularly carried out on women aged between 25-64 years. If you are not up to date with your smear tests then your doctor may arrange for this to be carried out.