Spotting between periods is usually caused by hormonal shifts, but it can also signal infections, structural changes in the uterus, pregnancy, or side effects from birth control. Most causes are not dangerous, though some need attention. Here’s a breakdown of the most likely reasons and what to look for.
Hormonal Shifts and Ovulation
The most common reason for light spotting is a temporary drop in estrogen. This happens naturally around the midpoint of your cycle, right after ovulation. When estrogen dips, a small amount of your uterine lining can shed, producing pink or brown spotting that lasts a day or two. In a 28-day cycle, this typically shows up around day 14.
Stress, whether emotional or physical, can also disrupt the hormonal signals that regulate your cycle. High stress triggers the release of cortisol, which interferes with the hormones responsible for ovulation. Extreme exercise and significant weight changes do the same thing. The result can be irregular cycles, skipped periods, or spotting at unexpected times. Your body is essentially signaling that conditions aren’t ideal for ovulation, and the disrupted hormone levels cause the uterine lining to shed unevenly.
Birth Control and Breakthrough Bleeding
Spotting is one of the most common side effects of hormonal contraception. It happens more often with low-dose and ultra-low-dose birth control pills, hormonal IUDs, and implants. If you’ve recently started or switched methods, your body needs time to adjust to the new hormone levels.
The adjustment timeline depends on the method. With a hormonal IUD, spotting and irregular bleeding in the first few months is normal and usually improves within two to six months. The implant is different: whatever bleeding pattern you have in the first three months tends to be your pattern going forward. Smoking, skipping pills, or taking hormones continuously to skip periods all increase the likelihood of breakthrough bleeding. Emergency contraception pills can also trigger irregular spotting.
Implantation Bleeding in Early Pregnancy
If there’s any chance you could be pregnant, the spotting may be implantation bleeding. This occurs when a fertilized egg attaches to the uterine lining, roughly six to twelve days after conception. It’s easy to mistake for a very light period, but there are clear differences.
Implantation bleeding is pink or brown, never bright red. It’s light enough that a thin liner can handle it, with no clots and no soaking through pads. It typically lasts a few hours to about two days, then stops on its own. If your bleeding is heavy, bright or dark red, or contains clots, it’s unlikely to be implantation. A home pregnancy test, taken after a missed period, is the fastest way to clarify things.
Infections and STIs
Certain infections cause inflammation of the cervix, which makes it more likely to bleed, especially after sex. Chlamydia and gonorrhea are the most common culprits. Chlamydia can cause bleeding between periods, while gonorrhea can trigger heavier intermenstrual bleeding. Both infections often produce no other obvious symptoms in the early stages, which is why spotting is sometimes the first sign something is off.
HPV can cause bleeding during or after sex. Trichomoniasis causes irritation and inflammation that can also lead to spotting. If your spotting is accompanied by unusual discharge, odor, or pelvic discomfort, getting tested for STIs is a straightforward next step. These infections are treatable, and early detection prevents complications.
Polyps and Fibroids
Uterine polyps are small growths that develop on the inner wall of the uterus when cells in the lining overgrow. They range from the size of a sesame seed to the size of a golf ball and are almost always noncancerous. They’re most common in people approaching or past menopause, but younger people get them too. Symptoms include spotting between periods, unpredictable cycle lengths, and unusually heavy periods.
Fibroids are similar growths made of muscle tissue in the uterine wall. Like polyps, they can cause irregular bleeding, heavy periods, and spotting. Both conditions are typically diagnosed with an ultrasound. Many polyps and fibroids don’t require treatment unless they’re causing significant symptoms or affecting fertility.
Perimenopause
If you’re in your 40s or early 50s, spotting may be an early sign of perimenopause. During this transition, hormone levels fluctuate unpredictably, causing your periods to behave differently than they have for years. You might skip a month, then have regular periods for a few months, then skip several months in a row. Cycles also tend to get shorter, so periods may come closer together than you’re used to.
Spotting between these increasingly irregular periods is common during this phase. However, any bleeding that occurs after you’ve gone a full 12 months without a period (meaning you’ve reached menopause) is not normal and should be evaluated.
When Spotting Needs Urgent Attention
Most spotting resolves on its own or has a straightforward explanation. But certain patterns signal something more serious. You should seek prompt evaluation if:
- Volume is high: soaking through a pad or tampon every hour for two to three hours straight
- Duration is prolonged: bleeding that lasts longer than a week
- Pregnancy is possible: any vaginal bleeding when you are or could be pregnant
- Severe pain accompanies it: especially pain that occurs outside your normal menstrual window
- A pattern change persists: periods that have been heavier or longer than usual for three or more consecutive cycles
- Spotting after menopause: any bleeding after 12 months without a period
Occasional light spotting that lasts a day or two, matches up with ovulation timing, or follows a birth control change is rarely cause for concern. Spotting that’s new, persistent, or accompanied by pain or other symptoms points toward something that benefits from a proper evaluation.