Spotting between periods is common, affecting up to 35% of people with menstrual cycles at some point during their reproductive years. Most of the time, the cause is something harmless like a temporary hormone shift or your body adjusting to birth control. But because spotting can also signal infections, growths, or early pregnancy, understanding the possible causes helps you figure out whether what you’re experiencing needs attention.
Ovulation Spotting
The most common harmless cause of mid-cycle spotting is ovulation. About two weeks before your next period, your body releases an egg. Right after that release, estrogen levels drop briefly before progesterone rises to take over. That quick hormonal dip can cause a small amount of uterine lining to shed, producing light spotting that’s typically pink or brownish.
Ovulation spotting usually lasts only one to two days and is light enough that you’d notice it on toilet paper or as a faint streak in your underwear, not something that fills a pad. If you track your cycle and the spotting consistently shows up around day 12 to 16, ovulation is the likely explanation. It doesn’t mean anything is wrong with your fertility or hormones.
Birth Control and Breakthrough Bleeding
Hormonal contraception is one of the most frequent causes of spotting between periods, especially in the first few months after starting or switching methods. Your body needs time to adjust to the new hormone levels, and spotting during that window is so expected that doctors have a name for it: breakthrough bleeding.
How long it lasts depends on the method. With an IUD, spotting and irregular bleeding typically improve within two to six months of placement. With the implant, the pattern is different: whatever bleeding you experience in the first three months tends to be the pattern you’ll have going forward. If spotting on the implant hasn’t settled after that initial period, it’s worth discussing alternatives with your provider. Missing a pill, taking it at inconsistent times, or certain medications that interfere with absorption can also trigger breakthrough bleeding on the combination pill.
Implantation Bleeding in Early Pregnancy
If there’s any chance you could be pregnant, spotting 10 to 14 days after ovulation may be implantation bleeding. This happens when a fertilized egg attaches to the uterine lining. It looks different from a period in several ways: the color is usually pink or brown rather than bright or dark red, the flow is closer to typical vaginal discharge than menstrual bleeding, and it shouldn’t soak through a pad. It also resolves on its own, usually within about two days.
Implantation bleeding can be easy to confuse with an early period, especially if your cycles are irregular. A pregnancy test taken after the day your period was due will give you a reliable answer. If the bleeding is heavy, bright red, or contains clots, it’s not implantation bleeding.
Cervical and Uterine Infections
Sexually transmitted infections, particularly chlamydia and gonorrhea, can inflame the cervix to the point where it bleeds easily. The cervical tissue becomes fragile, and even minor contact (like sex or a pelvic exam) can trigger spotting. Some people also notice spotting between periods without any obvious trigger, along with unusual discharge that may look yellowish or have an odor.
Herpes can cause a similar pattern, producing small sores or raw areas on the cervix that bleed with minimal irritation. The tricky part is that cervical infections don’t always cause pain or obvious symptoms, so spotting may be the only sign. If you’re sexually active and the spotting is new or accompanied by discharge, pelvic discomfort, or bleeding after sex, testing for STIs is a straightforward next step.
Polyps and Fibroids
Uterine polyps are small, soft growths that form on the inner wall of the uterus when lining cells overgrow. They’re sensitive to estrogen, meaning they grow in response to your body’s natural hormone fluctuations. Polyps are a well-known cause of bleeding between periods, and some people also notice heavier or more irregular periods alongside the spotting. Others have polyps with no symptoms at all, discovered incidentally during an ultrasound.
Fibroids, which are noncancerous muscular growths in or on the uterus, can cause similar spotting, particularly when they grow near the uterine lining. Both polyps and fibroids are common. They’re not cancerous in the vast majority of cases, but because they can cause persistent spotting that doesn’t resolve on its own, they’re worth investigating if your symptoms are ongoing. An ultrasound is the standard first step for detecting them.
Perimenopause
If you’re in your mid-40s or older, erratic spotting may be one of the earliest signs of perimenopause. During this transition, which can last several years before periods stop entirely, your ovaries gradually produce less estrogen. But the decline isn’t smooth. Hormone levels fluctuate unpredictably from cycle to cycle, which means your uterine lining doesn’t always build up and shed on a regular schedule. The result can be spotting between periods, cycles that are shorter or longer than usual, or periods that vary dramatically in flow from one month to the next.
Irregular bleeding during perimenopause is expected, but it’s also the age range when the risk of uterine abnormalities increases. New or worsening spotting in your 40s and 50s deserves a medical evaluation, even if perimenopause seems like the obvious explanation.
Other Possible Triggers
Several less common causes can also produce spotting between periods. Thyroid disorders disrupt the hormonal signaling that controls your cycle, and both overactive and underactive thyroid function can lead to irregular bleeding. Significant stress or rapid weight changes can suppress ovulation temporarily, causing hormonal shifts that trigger spotting. Cervical irritation from a recent pelvic exam, vigorous sex, or a dislodged IUD can also cause brief, light bleeding that resolves within a day or two.
Signs That Need Prompt Evaluation
Most spotting between periods turns out to be benign, but certain patterns warrant faster attention. Spotting that happens every cycle or persists for more than a few months is worth investigating, even if the amount is small. Bleeding after sex that recurs is a separate red flag, since it can point to cervical changes that need examination.
Seek emergency care if you’re soaking through a pad or tampon every hour for more than two hours in a row, especially if you also feel lightheaded, dizzy, or short of breath. That level of bleeding, whether it happens mid-cycle or during a period, can indicate a serious issue that needs immediate treatment. For anyone who has already gone through menopause, any vaginal bleeding at all is considered abnormal and should be evaluated promptly.