Chlamydia and gonorrhea are the two most common infections that cause bleeding between periods. Both infect the cervix, triggering inflammation that makes the tissue fragile and prone to bleeding on its own or after sex. Other infections, including bacterial vaginosis and trichomoniasis, can also lead to spotting, though they typically do so by first causing cervicitis, an inflammation of the cervix.
Infection-related bleeding usually comes with other clues: unusual discharge, pelvic pain, pain during sex, or fever. If your spotting showed up alongside any of these, an infection is a likely explanation worth investigating.
Chlamydia
Chlamydia is the single most common bacterial STI, and bleeding between periods is one of its hallmark symptoms in women. The infection settles into the cells lining the cervix and triggers inflammation that weakens the tissue surface, making it bleed easily. You may also notice unusual vaginal discharge and pain during sex. The tricky part is that chlamydia often produces mild or no symptoms at all, so spotting between periods may be the only visible sign something is wrong.
Left untreated, chlamydia carries real consequences. In the year after an untreated infection, roughly 1 in 10 women develop pelvic inflammatory disease (PID), a deeper infection that spreads into the uterus and fallopian tubes. Once PID develops, 15 to 20 percent of those women go on to experience infertility. That progression is preventable: chlamydia is curable with a short course of antibiotics, typically lasting seven days.
Gonorrhea
Gonorrhea causes many of the same cervical changes as chlamydia but tends to produce more noticeable symptoms. Heavy menstrual bleeding or bleeding between periods is a recognized symptom, often accompanied by a thicker, sometimes yellowish vaginal discharge, pelvic pain, and painful urination. Rectal pain or discharge can also occur if the infection has spread there.
The risks of ignoring gonorrhea are even steeper than with chlamydia alone. When both infections are present at the same time, which happens frequently, up to 30 percent of women develop PID. Gonorrhea is treated with a single antibiotic injection, and because co-infection is so common, testing for both chlamydia and gonorrhea simultaneously is standard practice.
Bacterial Vaginosis and Cervicitis
Bacterial vaginosis (BV) is not an STI, but it can still lead to bleeding between periods. BV is an overgrowth of certain bacteria that naturally live in the vagina, and when that overgrowth spreads to the cervix, it causes cervicitis. The cervical tissue becomes irritated, inflamed, and sometimes develops open sores. Bleeding between periods, pelvic pain, and unusual discharge are all symptoms of cervicitis regardless of its cause.
Cervicitis can also result from STIs like chlamydia and gonorrhea, or from less common infections like trichomoniasis and herpes. The common thread is that the cervix becomes fragile. The surface cells, when exposed and inflamed, bleed easily with minimal contact or sometimes spontaneously. This is why bleeding during or after sex often accompanies between-period spotting when an infection is the cause.
How Infection Bleeding Differs From Hormonal Spotting
Not all spotting between periods points to an infection. Hormonal fluctuations around ovulation, changes in birth control, or early pregnancy can all cause light bleeding. The difference usually comes down to accompanying symptoms.
Infection-related bleeding tends to show up with at least one of the following:
- Unusual discharge that looks, smells, or feels different from normal
- Pain during sex or a burning sensation
- Lower abdominal or pelvic pain
- Fever, which suggests the infection may have spread deeper
- Painful urination
Hormonal spotting, by contrast, is typically light, short-lived, and painless. It often occurs around the midpoint of your cycle and isn’t accompanied by discharge changes or pain. If your spotting is new, persistent, or paired with any of the symptoms listed above, infection is a more likely explanation than a hormonal blip.
Blood in Urine vs. Vaginal Bleeding
Urinary tract infections can cause blood to appear when you wipe, but this is blood in the urine (hematuria), not vaginal bleeding. The distinction matters because UTIs don’t cause intermenstrual bleeding from the reproductive tract. However, the two can be easy to confuse. Blood from a vaginal infection can contaminate a urine sample, and blood from a UTI can look like vaginal spotting on toilet paper.
If you’re unsure where the blood is coming from, paying attention to timing helps. Blood that appears only during urination and comes with urgency, frequency, or burning is more consistent with a UTI. Blood that appears on underwear between bathroom visits, or that shows up during sex, points toward a vaginal or cervical source.
How Infections Are Diagnosed
When you report bleeding between periods, the standard workup includes a pelvic exam where a clinician visually inspects the cervix for redness, swelling, or sores. Swabs are taken to test for chlamydia and gonorrhea, and a separate sample can check for BV and trichomoniasis. The STI tests use a highly accurate method that detects the genetic material of the bacteria, so results are reliable even when symptoms are subtle.
A Pap smear may also be collected during the same visit to rule out cervical cell changes unrelated to infection. The goal is to identify or exclude infection first, since it’s the most treatable cause of intermenstrual bleeding. If the tests come back negative, your provider will look into hormonal causes, polyps, or other structural issues.
What Happens After Treatment
Both chlamydia and gonorrhea are fully curable, and the bleeding they cause typically resolves within a few weeks of completing antibiotics. BV-related cervicitis also clears with treatment, though BV itself has a higher recurrence rate than STIs.
The more important timeline involves what happens if infection goes untreated. PID can develop within weeks of initial infection, and the damage it causes to the fallopian tubes is often permanent. Even a single episode of PID significantly raises the risk of chronic pelvic pain and ectopic pregnancy in addition to infertility. Sexual partners also need treatment to prevent reinfection, which is one of the most common reasons symptoms return after antibiotics.
If bleeding between periods persists after your infection has been treated and confirmed cleared, that’s a signal to revisit your provider. Persistent bleeding with a negative infection screen points toward other causes that need their own evaluation.