Spotting, or light bleeding between periods, has a wide range of causes, from completely harmless hormonal shifts to conditions that need medical attention. Most of the time, spotting is linked to something benign like ovulation, a new contraceptive, or early pregnancy. But because spotting can also signal infections, structural changes in the uterus, or rarely something more serious, understanding the full picture helps you figure out what your body is telling you.
Ovulation Spotting
One of the most common and least concerning causes is ovulation itself. Around the midpoint of your cycle (day 14 in a typical 28-day cycle), your body releases an egg. Right after that happens, estrogen levels drop sharply, and for some people, that brief hormonal dip causes a small amount of uterine lining to shed. The result is light spotting that lasts a day or two, often with a pinkish or light brown color. It’s entirely normal and doesn’t require treatment.
Hormonal Contraceptives
If you’ve recently started or switched a hormonal birth control method, spotting is one of the most frequently reported side effects. Combined oral contraceptives cause unscheduled bleeding in roughly 10 to 18% of cycles, regardless of whether you take a pill, use a patch, or wear a ring. Progestin-only pills have even higher rates: about 40% of users report irregular cycles.
Hormonal IUDs follow a distinct pattern. Around 35% of users experience frequent or prolonged spotting in the first six months after insertion. That number drops dramatically over time, with only about 4% still dealing with excess bleeding after a year. In fact, nearly half of hormonal IUD users stop having periods altogether by the six-month mark. So if you’re in those early months with a new IUD and seeing spotting, it’s very likely to resolve on its own.
Missing a pill, taking it at inconsistent times, or interactions with other medications can also trigger breakthrough bleeding with any hormonal method.
Implantation Bleeding in Early Pregnancy
Light spotting about 10 to 14 days after conception is a well-known early sign of pregnancy. When a fertilized egg attaches to the uterine lining, it can cause a small amount of bleeding. Implantation bleeding is common, though not everyone notices it. It’s typically lighter than a period, lasts a shorter time, and may appear pink or brown rather than bright red. If you’re sexually active and notice spotting around the time your period would be due, a pregnancy test is a reasonable next step.
Infections and STIs
Sexually transmitted infections are an underrecognized cause of spotting. Chlamydia specifically lists bleeding between periods as a symptom. Gonorrhea can cause heavy menstrual bleeding or intermenstrual spotting. Both infections inflame the cervix and surrounding tissue, which makes the area more prone to bleeding, sometimes triggered by something as minor as sex or a pelvic exam.
The tricky part is that chlamydia and gonorrhea often produce few or no other obvious symptoms, especially early on. Spotting may be the only clue. Trichomoniasis, another common STI, causes irritation and inflammation that can also lead to irregular bleeding, though it more often presents with discharge and discomfort first. If spotting is new and you have any reason to suspect exposure, testing is straightforward and treatment is effective.
Fibroids and Polyps
Structural growths in the uterus are a frequent cause of spotting, particularly in your 30s and 40s. Endometrial polyps are small tissue overgrowths on the uterine lining. They bleed because blood pools within the polyp, creating congestion that eventually leads to tissue breakdown at the tip. Most polyps are made of tissue that doesn’t respond to normal hormonal signals the way the rest of the lining does, so they don’t shed with your period like healthy tissue. Instead, they bleed unpredictably between cycles.
Fibroids (benign muscle tumors in the uterine wall) work differently. Submucosal fibroids, the type that grows into the uterine cavity, are most likely to cause spotting or heavy bleeding because they distort the lining. Many fibroids cause no symptoms at all, and whether they need treatment depends on their size, location, and how much they affect your daily life. Both polyps and fibroids are overwhelmingly benign, but they’re worth identifying because they rarely resolve on their own.
Perimenopause
If you’re in your 40s and your cycle has started behaving unpredictably, perimenopause is a likely explanation. During this transition, estrogen and progesterone levels rise and fall erratically rather than following the smooth pattern of earlier reproductive years. You may skip ovulation in some cycles, which means progesterone never rises to stabilize the uterine lining. The result can be shorter cycles, longer cycles, heavier flow, lighter flow, or spotting between periods. Some months may look perfectly normal, and others may be completely off schedule.
This phase can last several years before menstruation stops entirely. While irregular bleeding during perimenopause is expected, new or changing patterns are still worth mentioning to a healthcare provider, especially heavy or prolonged episodes, because conditions like polyps and thyroid dysfunction become more common in this age range too.
Ovulatory Dysfunction and Thyroid Issues
Your body needs consistent ovulation to produce the right sequence of hormones that builds and then cleanly sheds the uterine lining each month. When ovulation doesn’t happen reliably, bleeding becomes irregular. Polycystic ovary syndrome (PCOS) is one of the most common causes of this pattern, leading to infrequent, irregular, or prolonged bleeding. Thyroid disorders, both overactive and underactive, can disrupt ovulation in similar ways. So can significant stress, rapid weight changes, or excessive exercise, all of which affect the hormonal signals that regulate your cycle.
Medications Beyond Contraceptives
Hormonal contraceptives aren’t the only medications that cause spotting. Blood thinners (anticoagulants) are a well-known culprit because they reduce your blood’s ability to clot, which can turn what would normally be invisible micro-bleeding into noticeable spotting. Tamoxifen, used in breast cancer treatment, affects the uterine lining and commonly causes irregular bleeding. Even some herbal supplements that have estrogenic effects can shift your cycle enough to cause spotting.
Postmenopausal Bleeding
Any bleeding after you’ve gone 12 full months without a period counts as postmenopausal bleeding and needs evaluation. Most of the time, the cause turns out to be something benign: vaginal or endometrial thinning from low estrogen, polyps, or a hormonal shift. But 1 to 14% of people with postmenopausal bleeding, depending on age and risk factors, are found to have endometrial cancer. That range is wide because risk rises with factors like obesity, diabetes, and prolonged estrogen exposure without progesterone. The key point is that postmenopausal spotting, even a single episode, should always be investigated.
When Spotting Needs Urgent Attention
Most spotting resolves on its own or turns out to be something manageable. But certain patterns signal a more urgent situation. Spotting that comes with severe pelvic pain could indicate an ectopic pregnancy, ovarian torsion, or another acute condition. Bleeding heavy enough to soak through a pad every hour for several consecutive hours is not spotting anymore; it’s hemorrhage. Feeling lightheaded, dizzy, or faint alongside vaginal bleeding suggests enough blood loss to affect circulation.
Outside of those emergencies, spotting that persists for more than a couple of cycles, gets progressively heavier, or starts after menopause warrants a medical evaluation. The process typically involves a pelvic exam, blood work to check hormone levels and rule out infection, and sometimes an ultrasound to look at the uterine lining. Most causes of spotting are highly treatable once identified.