Guides

What causes bleeding between periods?

By the Plum team · Updated October 1, 2026
This page is general information, not medical advice. For questions about your own cycle or health, talk to a doctor, nurse, or other clinician who knows you.

Bleeding you don’t expect can be unsettling. Maybe it’s a brown smudge a week after your period finished, or a pink streak in the middle of the month. Sometimes it’s a few days of light bleeding that stops before you’ve worked out what it was.

It’s usually not serious, and a doctor should always check it.

What counts as bleeding between periods

Any bleeding or spotting outside your period counts, however light. The American College of Obstetricians and Gynecologists groups it under abnormal uterine bleeding. That category also covers bleeding after sex, periods that soak through a pad or tampon every hour, bleeding that lasts more than 7 days, cycles longer than 35 days or shorter than 21, cycle lengths that vary by more than 7 to 9 days, no period for 3 to 6 months, and any bleeding after menopause.

The word abnormal sounds alarming, but here it only means a doctor should look into it. Plenty of what lands in the category turns out to be a contraceptive settling in or a harmless growth.

Spotting often gets logged as if it were a period, and the two are different. Spotting is light, often brown or pink, and doesn’t need a pad. Day 1 of a cycle is the first day of real flow. If you record a spot as a period start, every cycle length and every prediction that follows it is wrong. So is the record you take to a doctor. If you’re not sure whether a second bleed this month was a period, the guide to two periods in one month walks through it.

The common causes

The NHS puts three causes at the top for bleeding between periods.

  • Hormonal contraception. Breakthrough bleeding is a known effect of the pill, the implant, the injection and hormonal coils, and it’s most common in the first few months of a new method. ACOG lists the copper coil separately as a cause of heavier periods, especially in the first year. The guide to tracking your period on birth control covers how to log this kind of bleeding.
  • Polyps and fibroids. These are small growths in or around the womb or on the cervix. Both are non-cancerous, and both can cause irregular bleeding.
  • Sexually transmitted infections. The NHS names chlamydia. That’s a large part of why the NHS suggests a sexual health clinic as well as a GP, and why a swab is a standard part of the appointment.

ACOG adds several more.

  • Problems with ovulation. Cycles where you don’t ovulate can bleed irregularly. This covers the first years after periods start, perimenopause, and conditions including PCOS and an underactive thyroid.
  • Adenomyosis. The lining of the womb grows into the muscle wall. Heavy bleeding and period pain that gets worse with age are the signs.
  • Bleeding disorders. Raise this if your periods have been heavy since they first started, or if you bruise easily, bleed after dental work or get frequent nosebleeds.
  • Medications. Blood thinners and aspirin can make menstrual bleeding heavier.
  • Cancer of the womb lining. It’s uncommon, and most cases are diagnosed in women past menopause, in their mid-60s. It’s on this list because abnormal bleeding is an early sign and early treatment works well.

Pregnancy is a separate case. Implantation bleeding can happen at the start of a pregnancy, and a pregnancy test is usually the first thing a doctor does at the appointment.

When it’s urgent

Two situations can’t wait for a routine appointment.

  • A missed period, unusual bleeding and abdominal pain together. The NHS says to ask for an urgent GP appointment or get help from NHS 111, because this can be a sign of an ectopic pregnancy.
  • Soaking through a pad or tampon every hour for more than two hours, with chest pain, shortness of breath, or feeling lightheaded or dizzy. ACOG says to seek emergency care straight away.

Any bleeding after menopause needs checking on its own, without waiting to see whether it happens again.

What happens at the appointment

The NHS describes a fairly short list. The doctor asks about your symptoms and history, and you may have a pregnancy test, a blood test, a test for sexually transmitted infections by urine sample or swab, and an examination of the vagina and cervix. If you need more tests, the next ones are an ultrasound scan, a colposcopy, or a hysteroscopy. A hysteroscopy uses a thin lighted scope that lets a doctor see inside the womb.

Treatment depends on the cause, so there’s not much point reading ahead on that. When the cause is a problem with ovulation, hormonal methods are often the first thing doctors try. If you don’t want contraception, say so. You can talk it through before you decide.

What to bring

ACOG asks you to keep track for several weeks beforehand and to note the dates, the length, and the type of bleeding, meaning light, medium, heavy or spotting. It says a cycle-tracking app is a fine way to keep that record.

Bring these with you:

  • Every bleeding day, with spotting marked as spotting.
  • The first day of each real period, so your cycle length and how much it varies can be read off the record.
  • Which contraception you use and the date you started or changed it.
  • Pain, and where it was.
  • Bleeding after sex, which is asked about separately.

Keeping a period diary turns a vague account into something a clinician can act on in the ten minutes you have.

How Plum fits in

We build Plum, a period tracker app, so here’s what it does and what it can’t do. Plum won’t tell you what your bleeding means. No app can, because telling the causes above apart takes a swab and a scan.

It keeps the record ACOG asks for. Logging a day takes a tap, and Plum records spotting as spotting, separate from your period. You choose which categories to track, so you can keep it to bleeding alone or add pain, mood and the rest. Plum works out your usual cycle length from what you log and predicts the next period. If your cycles are irregular, it says so, and it won’t pretend to know the date.

Plum shows no ads and never sells personal data. It does require an account, and it syncs your data to our servers, encrypted in transit and at rest. You can delete your account and data in the app at any time. If you’re in a group, the group sees a summary of your cycle dates and never your symptoms or moods.

Common questions

Is bleeding between periods normal?

It's common and usually not serious, but don't treat it as normal. The NHS says bleeding between periods can have many causes and a doctor should always check it. The American College of Obstetricians and Gynecologists counts any bleeding or spotting between periods as abnormal uterine bleeding. That's a category to investigate rather than a diagnosis in itself.

What causes spotting between periods?

The most common causes the NHS lists are hormonal contraception, small growths in or around the womb such as polyps or fibroids, and sexually transmitted infections such as chlamydia. ACOG adds problems with ovulation, which include PCOS and an underactive thyroid. It also lists adenomyosis, bleeding disorders, some medications including blood thinners, and, less often, cancer of the lining of the womb.

Does spotting mean I am pregnant?

Sometimes, and a pregnancy test is one of the first things a doctor will do. Implantation bleeding can happen at the start of a pregnancy. The NHS says to ask for an urgent GP appointment or call 111 if you've recently missed a period, have unusual bleeding and have pain anywhere in your abdomen. That combination can be a sign of an ectopic pregnancy.

Is spotting on the pill something to worry about?

Breakthrough bleeding is a recognised effect of hormonal birth control and is most common in the first few months of a new method. That doesn't make it a reason to skip the appointment. Tell your doctor which method you're on and when you started it, because that changes what they look for.

What is the difference between spotting and a period?

Spotting is light bleeding that doesn't need a pad or a tampon. It's often brown or pink rather than red, and it happens outside the days you'd call your period. A period is your regular flow, and day 1 of a cycle is the first day of real bleeding. Log them separately, because a spot logged as a period start makes every prediction after it wrong.

When is bleeding between periods an emergency?

ACOG says to seek emergency care if you're changing a pad or tampon every hour for more than two hours in a row and you also have chest pain, shortness of breath, or feel lightheaded or dizzy. The NHS says to get urgent help if you've recently missed a period, have unusual bleeding, and have abdominal or pelvic pain.

What should I write down before my appointment?

ACOG asks you to note the dates, the length and the type of bleeding for several weeks before the visit. Type means light, medium, heavy or spotting. ACOG says a cycle tracking app is a fine way to keep that record. Add which contraception you use, when you started it, and any pain.

Track it with PlumA period tracker for iPhone with no ads.

Plum logs your period in two taps and predicts your next period, fertile window and ovulation. We never sell your data.

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Why did my period come early?A period a few days early is usually a normal cycle. See what 3, 5, 7 or 10 days early means, when it could be spotting or pregnancy, and when to see a GP.Why did I get two periods in one month?Two periods in one month is often a normal cycle of 21 to 30 days. Here's how to tell, what a gap under 21 days can mean, and when to see a GP.What happens on each day of your cycle?What's happening on day 14, day 19 or day 25 of your cycle, what you may feel, and why it's usually too early for pregnancy symptoms or a test.
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