Spotting between periods is common and usually not a sign of something serious. The most frequent causes are hormonal shifts, birth control, ovulation, infections, and structural changes like polyps or fibroids. That said, the reason behind your spotting depends on your age, whether you use contraception, and what other symptoms you’re experiencing.
Ovulation Can Cause Mid-Cycle Spotting
One of the most common and harmless causes of spotting is ovulation itself. In the days leading up to ovulation, estrogen levels climb steadily. Once the egg is released, estrogen dips and progesterone starts to rise. That sudden hormonal shift can trigger light bleeding or spotting that’s much lighter than a regular period. This typically happens around day 14 of your cycle, though it can occur earlier or later depending on your individual pattern.
Ovulation spotting is usually brief, lasting a day or two at most, and the blood is often light pink or brown. If you notice a pattern of faint spotting roughly midway through your cycle each month, ovulation is the likely explanation.
Birth Control Is a Major Cause
Hormonal contraceptives are one of the most common reasons for spotting between periods, and the medical term for it is breakthrough bleeding. It happens more often with low-dose and ultra-low-dose birth control pills, the implant, and hormonal IUDs. Smoking increases the likelihood, as does taking pills inconsistently or skipping doses. If you use pills or a ring on a continuous schedule to skip periods altogether, breakthrough bleeding is especially common.
How long it lasts depends on the method. With an IUD, spotting and irregular bleeding in the first few months after placement is normal and typically improves within two to six months. The implant works differently: the bleeding pattern you have in the first three months is generally the pattern you can expect going forward. Emergency contraception can also trigger irregular bleeding as a one-time side effect.
Certain infections, including chlamydia and gonorrhea, can also increase the risk of breakthrough bleeding in people who use birth control. So if spotting is new, persistent, or accompanied by unusual discharge or pelvic pain, an infection may be compounding the issue.
Infections and Pelvic Inflammatory Disease
Sexually transmitted infections like chlamydia and gonorrhea can cause spotting on their own, even without birth control in the picture. These infections can inflame the cervix or the lining of the uterus, and that inflammation leads to bleeding between periods. Left untreated, they can progress to pelvic inflammatory disease (PID), an infection of the reproductive organs that lists bleeding between periods as one of its hallmark symptoms.
The tricky part is that many people with these infections have no symptoms at all, or only mild ones they dismiss. Spotting between periods, unusual discharge, pain during sex, or a dull ache in the lower abdomen are all reasons to get tested. PID is treatable, but delays can lead to more serious complications.
Polyps, Fibroids, and Other Structural Causes
Sometimes the cause isn’t hormonal but physical. Uterine polyps are small growths on the lining of the uterus, and cervical polyps grow on the cervix. Both can cause irregular bleeding or spotting, particularly after sex. Fibroids, which are noncancerous growths in the wall of the uterus, are another common structural cause. They vary widely in size, and not all fibroids cause symptoms, but those that press on or distort the uterine lining often trigger bleeding between periods or heavier-than-normal periods.
Adenomyosis, a condition where tissue similar to the uterine lining grows into the muscular wall of the uterus, can also cause spotting along with heavy periods and pelvic pain. These structural causes are typically identified through an ultrasound or similar imaging.
Could It Be Implantation Bleeding?
If pregnancy is a possibility, the spotting you’re seeing could be implantation bleeding. This happens when a fertilized egg attaches to the uterine lining, typically 10 to 14 days after ovulation. Because of the timing, it often shows up right around when you’d expect your period, which makes it easy to confuse the two.
A few characteristics set implantation bleeding apart. The color is usually pink or brown, not bright or dark red. The flow is extremely light, more like discharge than a period, and it shouldn’t soak through a pad or produce clots. It also resolves on its own within about two days. If what you’re seeing is heavier, contains clots, or is bright red, it’s likely something else. A pregnancy test taken after a missed period is the simplest way to confirm or rule this out.
Spotting in Your 40s and Perimenopause
If you’re in your 40s and noticing changes in your cycle, perimenopause is a likely factor. During this transition, periods can become shorter or longer, closer together or further apart, and heavier or lighter than what you’re used to. You may also skip periods entirely for a month or two.
While cycle irregularity is expected during perimenopause, bleeding or spotting between periods is not considered a normal part of this transition. ACOG specifically flags intermenstrual bleeding during perimenopause as something worth evaluating, because the risk of conditions like endometrial hyperplasia (thickening of the uterine lining) and uterine cancer increases with age. This doesn’t mean spotting in your 40s is automatically dangerous, but it does mean it warrants a conversation with your provider rather than being chalked up to “just perimenopause.”
Other Contributing Factors
Several less obvious factors can cause or contribute to spotting. Stress affects the hormonal signals that regulate your cycle and can lead to unexpected bleeding. An underactive thyroid disrupts these same hormonal pathways. Blood-thinning medications make bleeding of all kinds, including intermenstrual spotting, more likely. Even a routine pelvic exam or cervical biopsy can cause a small amount of spotting afterward, which is normal and temporary.
When Spotting Needs Attention
A single episode of light spotting mid-cycle, especially if you’ve recently started or changed birth control, is rarely cause for alarm. But certain patterns and symptoms signal that something more significant may be going on. Spotting that happens consistently after sex can point to cervical polyps, infections, or cervical changes that need evaluation. Spotting accompanied by pelvic pain, fever, or unusual discharge raises concern for infection or PID. And any intermenstrual bleeding that’s new and persistent in your 40s or beyond deserves investigation to rule out precancerous or cancerous changes.
If you’re ever soaking through pads or tampons every hour for more than two hours straight, and you’re also experiencing chest pain, shortness of breath, or dizziness, that’s a medical emergency requiring immediate care.