21 reasons why you may be bleeding between periods

Bleeding between periods can be both frustrating and concerning. More often than not however, spotting is not indicative of a serious medical issue. Noting the timing of the spotting, how long it lasts, and other relevant details such as blood colour and consistency, can help determine what's causing it. It's not always clear when you are spotting - to identify the difference between that and menstrual bleeding, check out our guide to spotting vs menstrual bleeding. 

We've identified 21 reasons for breakthrough bleeding, from most common to rare and potentially life threatening. As always, if you are concerned about anything you read, please seek professional medical advice.

For many girls, the first few years of menstruating are a confusing and unpredictable haze of painful and irregular menstrual cycles. Spotting during this time is normal, whilst the reproductive system figures out the nuances of menstruation.

Spotting is a common and normal side effect of starting, stopping, or switching birth control medications. Oestrogen helps keep the lining of the uterus in place. Changing the oestrogen or progesterone levels in your body as a result of varying birth control use could lead to spotting in between periods. This is usually just a short term side effect in the first three to six months, as your body adapts to changes in hormone levels. This is also true of all hormonal contraceptives, including the oral contraceptive pill, artificial progesterone injections, intrauterine devices (IUD) or the implant. Unscheduled bleeding is a common side effect of hormonal contraception, especially during the first few months of starting a new method. 

If you're taking combined oral contraceptives (the most common type of birth control pill), and the spotting continues after the first few months, you may want to try another brand with a different level of oestrogen. Additionally, continued spotting is more common with the hormonal IUD and the mini-pill (a progestin-only pill).

A. You Have a Decline in Oestrogen

One out of ten women experience light spotting during ovulation in their menstrual cycle because of a brief decline in oestrogen levels that occur when an egg is released from an ovary. Spotting can also occur due to reduction of the level of oestrogen which usually precedes ovulation. The decline in oestrogen causes women to experience brown vaginal discharge, or spotting, as well as cramping and discomfort.

B. Ovulation Pain 

When an ovary releases an egg, some women experience one-sided, lower abdominal pain or mittelschmerz (German for 'middle pain'). This usually occurs about fourteen days before your next period. Aside from mild pain, mittelschmerz can cause spotting. It is important to note that ovulation is when you are most fertile. Be sure not to mistake this type of spotting with menstrual bleeding!

C. You Have a Delayed or Partial Period

During a 'normal' period, menstrual blood consists of old blood, endometrial lining and dead tissue. When you have a delayed or partial period, small amounts of lining are left behind inside the uterus. When this remaining tissue finally expels, it takes the form of brownish discharge or blood.

Hormonal imbalances are one of the primary reasons for vaginal spotting between periods. A slow thyroid (hypothyroidism) is characterised by hormonal imbalances, and therefore has a significant effect on a woman's menstrual cycle.

Urinary Tract Infections (UTIs) can cause bleeding from the urethra. If you are finding it painful to urinate, and seeing a small amount of blood, a UTI could be the cause. Most UTIs are easily treated with a full course of antibiotics, as prescribed by your GP.

Anticoagulants or blood thinners are drugs that help prevent your blood from clotting or prevent existing clots from growing. One side effect of taking these drugs is unusual bleeding, either before your period or excessively during your period. Some antipsychotic and antidepressant medications which affect serotonin uptake can also cause spotting in women.

Emergency contraception, or the morning after pill, can cause light spotting. Although it is not a side effect, the medication's hormones can cause bleeding. Whilst this is completely normal, it is important to note that this does not indicate you have had your period, and therefore does not signify you are not pregnant. Usually when you've taken emergency contraception, you'll get your period sooner than scheduled. It is also common for the second cycle, and period, to be slightly longer.

Inserting something into your vagina such as a tampon, penis or sex toy can cause spotting. Sex when your vagina isn’t lubricated enough, or with a very well endowed partner can cause small tears and therefore bleeding. Cervical bleeding can also occur during very deep penetration, or if your vaginal opening is small. Using an artificial lubricant and ensuring arousal before sex can prevent damage to the vagina during sexual activity. Inserting a tampon when you are too dry or too forcefully can also cause spotting.

STIs can cause vaginal bleeding. Chlamydia and gonorrhoea are the most common examples. As well as spotting between periods, bleeding during or after sex can occur. If left untreated, both chlamydia and gonorrhoea can cause serious health issues such as Pelvic Inflammatory Disease (see below) and even infertility. It's always a good idea to get tested for STIs after unprotected sex with a new partner, especially as chlamydia does not often cause symptoms.

Cervicitis is inflammation or irritation of the cervix, most commonly caused by an STI. Whilst the symptoms, such as vaginal discharge, itching, pain with intercourse, and spotting, are very uncomfortable, cervicitis is easily diagnosed and treated by a GP.

Pelvic Inflammatory Disease (PID) occurs when certain pelvic infections, caused by STIs or use of IUDs, go untreated. Aside from spotting, symptoms include pain in the lower abdomen, unusual vaginal discharge and pain during sex. PID is a serious condition that can affect a woman's fertility, but when detected, can be easily treated with antibiotics. Find out more here. 

Many people experience some bleeding after having a termination. Spotting may last for several weeks after having an in-clinic procedure or taking the abortion pill. If bleeding is very heavy, seek medical advice. for further information, visit the NHS website. 

Spotting or 'implementation bleeding' may occur in the early stages of pregnancy. It typically occurs 10 to 14 days after conception, when the fertilised egg attaches to the uterine lining, and before the mother's period is due. Implementation bleeding is normal very early in pregnancy, but unlike menstrual blood, is usually a pink or brown coloured discharge. Bleeding in early pregnancy could also be a symptom of an ectopic pregnancy. This is a pregnancy that is growing somewhere other than the uterus, usually the fallopian tube. Ectopic pregnancy bleeding is often coupled with other symptoms including abdominal pain on one side, pelvic pain, shoulder pain, and/or dizziness. Seek immediate medical help if you experience symptoms of an ectopic pregnancy.

Bleeding is one early sign of a miscarriage. In the unfortunate case of an impending miscarriage, the mother may experience abdominal cramping, back pain, lower abdominal pain and spotting. Miscarriages most commonly occur in the first 20 weeks of pregnancy. 

In the postpartum phase, new mothers often experience spotting and irregular bleeding as opposed to their pre-pregnancy menstrual periods. Whilst breast-feeding suppresses ovulation, many women experience spotting during this time. 

Spotting between periods can also be caused by ovarian cysts - small sacs filled with liquid that develop in your ovaries. In more extreme cases, ovarian cysts can rupture, causing lower pelvic pain, spotting, and severe discomfort. Normally, doctors will wait and see if the cysts resolve themselves. If they don’t, they can be surgically removed. Women with polycystic ovary syndrome (PCOS) have a hormonal imbalance that interferes with normal ovulation and therefore causes irregular periods and spotting. Other side effects include unwanted body hair, acne and weight gain. The most common treatment for PCOS is birth control or hormonal therapy.

Menopause is a natural part of the female ageing process, as a woman's oestrogen levels drop to levels which mean that the ovaries no longer produce eggs. This usually happens between the ages of 45 and 55, and is marked by an end to periods and natural fertility. According to the NHS, the average age for a woman in the UK to reach the menopause is 51. During the transitional phase leading up to this, known as perimenopause, unstable hormone levels can cause irregular periods, spotting, and heavy bleeding. Once you enter menopause, all menstrual bleeding should stop. 

If you are still bleeding into this stage however, consult your doctor immediately. Hormone replacement therapy (HRT), commonly used to relieve some of the symptoms of menopause, can also cause spotting. Women who are in menopause commonly experience vaginal dryness (or vaginal atrophy), as their ovaries are producing less oestrogen, causing a reduction in the number of lubricating glands. This can cause the vagina to feel itchy, dry and irritated. Using an artificial lubricant can help to prevent spotting caused by a tear to dry skin of the vagina. 

Adenomyosis occurs when tissue from the womb lining becomes embedded in the wall of the womb. The endometrial tissue thickens, breaks down, and bleeds, like it should in a normal menstrual cycle. However, an enlarged uterus can be painful and is one cause of heavy periods. 

Fibroids (also known as leiomyomas or myomas), are the abnormal growth of muscle tissue on your uterus, and can be to blame for spotting between periods. They range in size from tiny growths that are almost undetectable to the human eye, to large, bulky growths that can alter and enlarge your uterus. It is common for women to have uterine fibroids at some point in their life, and whilst often they present no symptoms, some women can experience heavy menstrual bleeding, spotting between periods, pelvic pressure or pain, frequent urination, and constipation.

Uterine Polyps, or Endometrial Polyps, are noncancerous growths which form when there is overgrowth of cells in the lining of the uterus. While polyps usually stay in the uterus, some can travel through the opening of the uterus (cervix) into the vagina. These are mainly found in women who are going through or have finished menopause. As well as unexpected bleeding, they may also cause irregular discharge, Polyps are often discovered during a smear test, and the majority of them are benign - but in rare cases, can be cancerous.

In rare cases, spotting may be a symptom of cancers related to the reproductive system - vaginal, cervical, uterine, ovarian. Endometrial cancer is the most common of the gynaecological malignancies, and the most curable. It arises from the glandular tissue within the uterine lining. Ovarian cancer is a growth of abnormal malignant cells that begins in the ovaries. Symptoms include bloating, pelvic or abdominal pain, difficulty eating or feeling full quickly, abnormal spotting, or urinary symptoms. Cervical cancer is detected through pap smears screenings and pelvic examinations. Vaginal spotting is the first type of symptom of the disease. Heavier vaginal bleeding, heavy vaginal discharge, and lower abdominal pain are other symptoms that occur. Early detection of these cancers is key. It is extremely important to get regular cervical screening test ,and talk openly to medical professionals about any symptoms you may be experiencing.

The most common reasons for vaginal bleeding between periods are hormonal contraceptives or changes relating to menopause. If bleeding between periods is very heavy or lasts for longer than 3 months, seek medical advice. Regular cervical screening is an essential part of preventive healthcare, especially for women between ages 25 and 65. Keeping a menstrual diary and recording changes to your flow or length of bleeding will make the diagnosis and prevention of abnormal bleeding much easier.

When to call a doctor

If you're concerned about your bleeding, you should:

• See your GP
• Visit a sexual health or genitourinary medicine (GUM) clinic

If you experience prolonged spotting or new and unexplained spotting book an appointment with your GP. Contact a doctor immediately if:

• You have recently experienced rape.
• You believe the spotting could be due to an injury.
• You are pregnant or could be pregnant.
• The spotting occurs after menopause.
• If it develops into heavy menstrual-like bleeding.
• If in addition to the spotting, you feel pain, exhausted or dizzy.

Disclaimer: Information on this site is provided as an informative resource only, and is not to be used or relied on for diagnostic or treatment purposes.