Bleeding Between Periods: Causes and When to Worry

Bleeding between periods is vaginal bleeding or spotting that occurs between one menstrual period and the next. It may appear as a few pink or brown spots or a light flow. Doctors call this intermenstrual bleeding, a form of abnormal uterine bleeding (AUB).¹²

Your period ended days ago, so seeing blood again can be confusing. Even a small pink or brown spot may leave you wondering whether your cycle has changed or something is wrong. Fortunately, most of the time the bleeding between periods can be reasonably explained. Even though contraception and hormonal changes are among the common causes, it can also be caused by infection, pregnancy, fibroids, or polyps. However, the bleeding pattern (and any associated symptoms) usually gives the most helpful clues.

On this page

1. What counts as bleeding between periods?
2. What can the bleeding pattern tell you?
3. Could hormones be causing the bleeding?
4. Can ovulation cause spotting?
5. Could birth control be responsible?
6. Could bleeding between periods mean pregnancy?
7. Why does bleeding sometimes happen after sex?
8. Can an infection cause bleeding between periods?
9. Could fibroids or polyps be causing the bleeding?
10. What if you are in perimenopause?
11. Does bleeding between periods mean cancer?
12. How is bleeding between periods diagnosed?
13. How is bleeding between periods treated?
14. When to see a doctor?

What counts as bleeding between periods?

Bleeding between periods usually occurs after a period has finished, but before the next one is expected. Healthcare professionals refer to this condition as intermenstrual bleeding (IMB).¹

It does not always look like a second period. You can notice pink-tinged mucus when you wipe, a couple of light brown spots in your underwear, or some light bleeding in your underwear that lasts for a day or two.

Color is often the first thing to grab your attention, but it doesn’t actually tell us why you are bleeding. Brown blood indicates the blood has been in the reproductive tract for some time; bright red indicates fresher blood.

The important thing is the pattern. Bleeding that occurs once is quite different from having spotting each month, repeatedly after sex, or having pelvic pain or abnormal vaginal discharge.

What can the bleeding pattern tell you?

Timing alone cannot tell us the cause, but it can help us determine what is going on.

The table is merely a guideline. Many different conditions may give rise to similar bleeding patterns, so persistent bleeding should be checked rather than assumed harmless.

Doctors often organize the causes for menstrual disorders using the International Federation of Gynecology and Obstetrics (FIGO) PALM-COEIN framework. PALM groups structural causes in the uterus, such as polyps and fibroids, while COEIN groups nonstructural causes, including ovulation problems, bleeding disorders, endometrial (uterine lining) causes, and medication-related bleeding.¹

Could hormones be causing the bleeding?

Hormonal fluctuations are one of the most common reasons. In a normal cycle, the uterine lining is stimulated to grow and then break down by the actions of estrogen and progesterone. If ovulation occurs later than expected or is absent, the hormones do not follow a usual pattern. As a result, the lining can then shed at an unexpected time.²

Intermenstrual bleeding due to hormonal changes is more common in conditions in which ovulation is unpredictable, as in the first few years after starting periods (menarche) or in perimenopause. Additionally, disorders that affect ovulation, such as PCOS (polycystic ovary syndrome), now known as PMOS (Polyendocrine Metabolic Ovarian Syndrome),¹¹ and thyroid problems, may alter bleeding patterns.²

One abnormal cycle doesn’t necessarily indicate a hormonal problem. But spotting is more significant when it accompanies increasingly irregular cycles or excessively long or short intervals between them.

Can ovulation cause spotting?

Women can also experience a tiny amount of spotting halfway through the cycle. This may occur around ovulation, but there may be other causes that should be discussed properly.¹

If the bleeding is mild, brief, and occurs at similar times in otherwise normal cycles, then this may coincide with ovulation. If the bleeding becomes more intense, painful, or irregular, then you should discuss this with your healthcare provider.

Could birth control be responsible?

Yes. Hormonal contraceptives might affect your bleeding pattern. This is especially common when first starting a method or switching from one method to another.

Breakthrough bleeding can happen with the pills, hormonal IUDs, implants, injections, patches, and vaginal rings. It is most common in the first few months as your uterine lining adjusts.³ If you take your pills irregularly or forget to take them for a couple of days, this can also cause spotting.

A copper IUD is different because it contains no hormones. It can cause spotting or heavier or longer bleeding, especially during the first few months after insertion.²

Breakthrough bleeding does not necessarily indicate that you have become pregnant. Certainly, protection against pregnancy will also depend on the type of contraception you are using, and whether it has been used correctly.

If you continue to have bleeding or if your bleeding becomes troublesome, discuss this with your doctor before stopping your method. Sometimes, the bleeding resolves on its own; other times, changing contraceptive methods will help.³

Could bleeding between periods mean pregnancy?

If there’s any chance you could be pregnant, keep that possibility in mind. Early pregnancy bleeding is common. Rest assured, it doesn’t always indicate that something is wrong with the pregnancy. In other cases, bleeding can also occur as a result of pregnancy loss or an ectopic pregnancy (when pregnancy occurs in the wrong place outside of the uterus, often in the fallopian tube).⁴

If you think your period is late, very light, or just different from usual, then home pregnancy tests are a good initial way to find out.

The symptoms associated with the bleeding are very significant. If you suspect pregnancy, go to the emergency room immediately if you experience any of the following⁴:

• Worsening pelvic pain on one side
• Severe abdominal pain
• Shoulder pain
• Dizziness or weakness
• Loss of consciousness

Why does bleeding sometimes happen after sex?

The cervix is made of soft tissue and blood vessels, so it is more prone to bleeding if inflamed or irritated. One possible reason is cervicitis, meaning an inflamed cervix.

According to the Centers for Disease Control and Prevention, cervicitis can be the source of intermenstrual bleeding, especially after sex.⁵ Some cases can be caused by sexually transmitted infections, such as gonorrhea or chlamydia.

Cervical changes, such as cervical polyps, can also be responsible for bleeding after sex, and therefore repeated episodes should be investigated rather than ignored.

Can an infection cause bleeding between periods?

Yes. If you have an infection in your cervix or reproductive organs, it could change your normal bleeding pattern.

Infections such as STIs can cause spotting due to an inflamed cervix. Spreading upward, an STI infection can cause pelvic inflammatory disease (PID, an infection of the upper female reproductive organs).⁶

PID can lead to intermenstrual bleeding, lower abdominal pain, abnormal vaginal discharge, dyspareunia (pain during sexual intercourse), fever, or dysuria (painful urination).⁶

However, some infections cause relatively few symptoms. So, you should rely on proper laboratory investigations for diagnosis.

Could fibroids or polyps be causing the bleeding?

Fibroids are benign tumors that are derived from the muscles of the uterus. While some may not produce any symptoms, others can result in abnormally heavy bleeding.⁷

Polyps are, more often than not, benign tumors that have developed from the lining of the uterus or cervix. The presence of polyps may cause spotting in between periods or after sex, depending on the site of the growth.²

As the symptoms cannot solely differentiate fibroids from polyps or hormonal issues, your doctor might want to do an ultrasound if bleeding persists.

If bleeding persists, an endometrial biopsy (a small sample taken from the uterine lining) may also be recommended when age or other risk factors make changes in the lining important to rule out.²⁸

What if you are in perimenopause?

During perimenopause, the fluctuation of your menstrual cycle can be irregular because the level of hormones is becoming unstable.

The duration of your periods may differ: they could be more frequent, less frequent, heavier, lighter, longer, or shorter.⁹ However, bleeding in between periods is not always considered a natural part of the transition into menopause.

Your doctor will determine whether additional tests are necessary based on your age, symptoms, medical history, and risk factors.² After 12 months of amenorrhea, any vaginal bleeding is classified as postmenopausal bleeding. This should always be investigated properly.⁹

Age also changes how abnormal bleeding is evaluated. ACOG recommends endometrial sampling as a first-line test for abnormal uterine bleeding in patients older than 45.⁸

Does bleeding between periods mean cancer?

The National Cancer Institute has included bleeding in between periods or after sex on the list of symptoms that could be due to cervical cancer.¹⁰

However, this does not mean that you should be worried about cancer with one episode of spotting. It means that if the bleeding persists or keeps coming back, then it needs to be investigated.

Being older than 45 does not mean that abnormal bleeding is cancer, but it lowers the threshold for checking the uterine lining. Persistent bleeding in younger patients may also need sampling when specific risk factors are present.⁸

How is bleeding between periods diagnosed?

Diagnosis starts with your bleeding pattern, medical history, medications, contraception, and whether pregnancy is possible. A pelvic exam, pregnancy test, and STI testing may be needed. If bleeding is heavy or prolonged, a complete blood count (CBC) can check for anemia (too few healthy red blood cells). Ultrasound or an endometrial biopsy (taking a sample of tissue from the inner lining of the uterus) may be recommended depending on your symptoms, age, and risk factors.²⁸

How is bleeding between periods treated?

Treatment depends on the cause rather than the bleeding alone. Hormonal treatment may help when ovulation or contraception is responsible, while infections need treatment for the specific infection. Polyps or fibroids sometimes require a procedure. If a contraceptive method is causing troublesome spotting, your healthcare provider can discuss whether an adjustment or another method is appropriate.²³

When to see a doctor?

One small episode of spotting alone may not warrant an urgent appointment, particularly if you are feeling well and have an obvious explanation such as having recently started hormonal contraception. The more the bleeding gets into a pattern, the more important it is to get it checked. Arrange an evaluation if you notice:

• Bleeding that keeps returning
• Bleeding that becomes heavier
• Repeated bleeding after sex
• Pelvic or lower abdominal pain
• Unusual vaginal discharge
• Fever or painful urination
• Significant alteration of your normal menstrual cycle
• Bleeding when pregnancy is possible

Intermenstrual bleeding that persists over time provides valuable clues to your doctor because it suggests a persistent effect on your usual pattern. If it keeps happening after sex, gets heavier, or is accompanied by pain, discharge, fever, or suspected pregnancy, you need proper consultation. You don’t have to figure out the cause on your own. Keep track of when it occurs, how much you are bleeding, and what your symptoms are, and have a doctor help you find the cause.

Frequently asked questions