Spotting between periods is extremely common and usually has a straightforward explanation. Hormonal shifts, birth control, ovulation, early pregnancy, and infections are among the most frequent causes. In most cases, light spotting resolves on its own, but understanding the pattern and any accompanying symptoms helps you figure out whether it needs attention.
Ovulation Can Trigger Mid-Cycle Spotting
One of the most common and harmless causes of spotting is ovulation itself. Estrogen drops right after an egg is released, and for some people, that brief hormonal dip causes a small amount of the uterine lining to shed. This typically shows up as light pink or brown spotting around the midpoint of your cycle. In a 28-day cycle, that means around day 14, though the exact timing depends on your cycle length. It’s usually just a trace amount lasting a day or two, and it doesn’t signal anything wrong.
Hormonal Birth Control and Breakthrough Bleeding
If you recently started, stopped, or switched a hormonal contraceptive, spotting is one of the most predictable side effects. This is called breakthrough bleeding, and it’s especially common with low-dose birth control pills, hormonal IUDs, and the implant. Smoking, skipping pills, or using hormonal methods continuously to skip periods all increase the likelihood.
The adjustment period varies depending on the method. With a hormonal IUD, irregular bleeding in the first few months is normal and typically settles down within two to six months. With the implant, the bleeding pattern you experience in the first three months tends to be the pattern you’ll have going forward, so it’s a useful early signal of what to expect. Emergency contraception pills can also cause irregular bleeding after use.
Implantation Bleeding in Early Pregnancy
About 1 in 4 pregnant people experience implantation bleeding, which happens when a fertilized egg attaches to the uterine lining. It typically occurs around the time you’d expect your period, which is why it’s easy to confuse the two. A few details help distinguish them. Implantation bleeding is usually brown, dark brown, or pink rather than the bright or dark red of a period. The flow is light and spotty, more like discharge than a true bleed, and it doesn’t require more than a panty liner. It also tends to be shorter, lasting hours to a couple of days rather than the four to seven days of a typical period.
If there’s any chance you could be pregnant and you notice spotting, a home pregnancy test is the simplest next step.
Infections and STIs
Certain infections cause inflammation in the cervix or uterus that leads to spotting, particularly after sex. Chlamydia and gonorrhea are two of the most common culprits, and both can progress to pelvic inflammatory disease (PID), an infection of the reproductive organs. PID can cause bleeding between periods, pain or bleeding during sex, unusual discharge, and lower abdominal pain. The tricky part is that many STIs cause no obvious symptoms early on, so spotting may be the first noticeable sign. If your spotting is accompanied by pelvic pain, fever, or unusual discharge, testing for STIs is an important step.
Polyps and Fibroids
Structural growths in the uterus are another well-known cause of spotting. Uterine polyps are small overgrowths of the uterine lining that attach to the inner wall by a base or thin stalk. They’re estrogen-sensitive, meaning they grow in response to estrogen levels in the body. Polyps can cause bleeding between periods, unpredictable cycles that vary in length and heaviness, very heavy periods, and spotting after menopause. Some people with polyps have only light spotting, while others have no symptoms at all.
Uterine fibroids, which are noncancerous muscle growths in the uterine wall, produce similar symptoms. Both polyps and fibroids are common, and neither is cancerous in the vast majority of cases, but they can affect fertility and quality of life if they cause persistent heavy or irregular bleeding.
Perimenopause and Life Stage Changes
If you’re in your 40s (or sometimes late 30s) and noticing spotting that wasn’t there before, perimenopause is a likely explanation. During this transition, estrogen and progesterone levels fluctuate unpredictably. Too much estrogen relative to progesterone can cause the uterine lining to thicken unevenly, a condition called endometrial hyperplasia. As parts of that lining thin or shed at irregular intervals, spotting and unpredictable bleeding follow. Cycles may get shorter, longer, heavier, or lighter before periods eventually stop altogether.
Any vaginal bleeding that occurs after menopause, meaning 12 consecutive months without a period, should be evaluated by a doctor regardless of how light it is.
Other Common Causes
Several additional factors can cause spotting:
- Stress can disrupt ovulation and shift hormone levels enough to cause irregular bleeding.
- Thyroid problems, particularly an underactive thyroid, interfere with the hormones that regulate your cycle.
- Blood thinners make it easier for small amounts of uterine lining to bleed through.
- Physical irritation from intercourse, a recent pelvic exam, or vaginal dryness can cause light bleeding from the cervix or vaginal walls.
- IUD placement commonly causes occasional spotting, especially in the months after insertion.
In rare cases, spotting can be a sign of cervical or uterine cancer, which is one reason persistent or unexplained bleeding is worth investigating even if it seems minor.
When Spotting Needs Medical Attention
Most spotting is harmless, but certain patterns warrant a closer look. Spotting during a known pregnancy should be reported to your care team right away. Bleeding that soaks through a pad or tampon every hour for four or more hours is considered very heavy and needs prompt evaluation. Spotting that comes with pelvic pain, fever, or foul-smelling discharge suggests infection. And any bleeding after menopause, no matter how light, should be checked.
How the Cause Gets Identified
If you see a doctor about spotting, expect a pelvic exam as the starting point. From there, common next steps include a pregnancy test, STI screening, and blood work to check for anemia, thyroid issues, or bleeding disorders. An ultrasound can reveal polyps, fibroids, or other structural changes. If the ultrasound shows something that needs a closer look, a hysteroscopy (a thin camera inserted through the cervix) or a small biopsy of the uterine lining may follow. The specific workup depends on your age, symptoms, and risk factors, so not everyone needs every test.