Brown spotting that lasts a full week usually means small amounts of blood are leaving your body slowly enough to oxidize and turn dark before it exits. The brown color itself isn’t alarming, but a week of continuous spotting has several possible explanations, ranging from normal hormonal shifts to conditions worth checking out. What’s behind it depends on your age, whether you use birth control, and whether you have other symptoms alongside the spotting.
Why Spotting Turns Brown
Fresh blood is red. When blood takes longer to travel from the uterus through the cervix and out of the vagina, it’s exposed to oxygen and breaks down, turning brown or dark brown. This is the same process that makes a cut on your skin darken as it heals. Brown spotting simply means the bleeding is light and slow. It’s not a different type of blood or a sign of a unique problem on its own.
Hormonal Shifts and Ovulation
If the spotting started roughly two weeks before your expected period, ovulation is a likely trigger. When your body releases an egg, estrogen levels drop sharply. That sudden dip can cause a small amount of the uterine lining to shed, producing light brown spotting that typically lasts one to three days. For some people, though, this bleeds into a longer stretch of on-and-off spotting, especially during cycles where hormone levels fluctuate more than usual.
Stress, poor sleep, significant weight changes, and intense exercise can all amplify hormonal fluctuations in a given cycle. If your body produces slightly less progesterone than normal in the second half of your cycle, the uterine lining becomes unstable and sheds in small amounts over several days rather than all at once during a proper period. This is one of the most common reasons for a week of light brown spotting that eventually resolves on its own.
Birth Control and Breakthrough Bleeding
Hormonal contraceptives are a frequent culprit. If you recently started a new pill, switched methods, or had an IUD placed, brown spotting for days or even weeks is part of the adjustment process. With IUDs, spotting and irregular bleeding in the first few months after placement is common and generally improves within two to six months. With the implant, the bleeding pattern you experience in the first three months tends to be the pattern going forward, so persistent spotting may be worth discussing with your provider.
Missing a pill or taking it at inconsistent times can also trigger breakthrough bleeding. The brief dip in hormone levels destabilizes the lining enough to cause light spotting that shows up brown on underwear or when wiping.
Implantation Bleeding in Early Pregnancy
If there’s any chance you could be pregnant, implantation bleeding is worth considering. When a fertilized egg attaches to the uterine lining, it can cause light spotting that is typically brown, dark brown, or pink. This usually happens before you’ve missed a period or taken a pregnancy test.
The key difference: implantation bleeding is short, lasting anywhere from a few hours to a couple of days. A full week of spotting is longer than what implantation alone typically causes, but if the timing lines up and you have other early pregnancy signs like breast tenderness or fatigue, a home pregnancy test is a reasonable next step.
PCOS and Irregular Ovulation
Polycystic ovary syndrome (PCOS) is one of the more common reasons for persistent brown spotting between periods. PCOS can prevent proper ovulation, which means the uterine lining builds up over time but doesn’t shed in a normal, complete period. Instead, parts of the lining break away irregularly, producing brown spotting that can last days. People with PCOS often have more than 35 days between cycles, and when bleeding does occur, it may be unpredictable in timing and color.
If you’ve noticed increasingly irregular cycles alongside the spotting, acne, excess hair growth, or difficulty losing weight, PCOS is worth investigating. Left unmanaged, the ongoing buildup of the uterine lining without regular shedding can lead to a condition called endometrial hyperplasia, where the lining becomes abnormally thick.
Polyps and Fibroids
Growths in the uterus can cause spotting between periods. Uterine polyps are small, estrogen-sensitive tissue growths on the uterine lining. They can cause irregular bleeding, spotting between periods, and unpredictable periods that vary in length and heaviness. Some people with polyps only have light spotting, while others experience heavier symptoms. Fibroids, which are noncancerous growths in the uterine wall, can cause similar patterns. Both are common, particularly in your 30s and 40s, and are typically found during an ultrasound.
Infections That Cause Spotting
Certain infections, including sexually transmitted infections like chlamydia and gonorrhea, can irritate the cervix or uterine lining enough to cause spotting. If the infection travels deeper, it can develop into pelvic inflammatory disease (PID). Symptoms of PID include lower abdominal pain, unusual discharge with a bad odor, pain or bleeding during sex, burning when you urinate, and bleeding between periods.
Brown spotting combined with any of these symptoms, particularly odor or pelvic pain, points toward an infection that needs treatment. PID can cause lasting damage to the reproductive organs if left untreated, so these symptoms warrant a prompt visit rather than a wait-and-see approach.
Perimenopause
If you’re in your 40s, shifting hormone levels associated with perimenopause can explain a week of brown spotting. During this transition, periods may become shorter or longer, heavier or lighter, and the days between cycles can vary widely. You may also skip periods entirely. As the uterine lining thins in response to fluctuating estrogen and progesterone, abnormal bleeding becomes more common. Spotting between expected periods, including prolonged brown discharge, fits this picture.
That said, abnormal bleeding during perimenopause still deserves evaluation. Endometrial hyperplasia, where the lining thickens excessively due to too much estrogen relative to progesterone, is more common during this stage and can, in some cases, progress to cancer if untreated.
When a Week of Spotting Needs Evaluation
A normal menstrual period generally lasts up to seven days. Bleeding that extends beyond seven days is classified as abnormal uterine bleeding. A week of brown spotting that replaces or follows a normal period sits right at that threshold, and if it continues beyond seven days or recurs cycle after cycle, it’s worth getting checked.
You should also pay attention if the spotting comes with pelvic pain, foul-smelling discharge, pain during sex, or fever. Spotting after menopause, regardless of color or amount, always warrants evaluation.
What to Expect at the Doctor
If you go in for persistent spotting, your provider will likely start with questions about your cycle history, birth control use, sexual activity, and any other symptoms. From there, common next steps include blood work to check hormone levels and rule out pregnancy, and a transvaginal ultrasound. This painless imaging test lets your provider see your uterus, cervix, fallopian tubes, and ovaries, and it can reveal abnormal growths like polyps or fibroids that might explain the bleeding. Sometimes the ultrasound alone is enough to identify the cause. Other times, additional imaging or a biopsy of the uterine lining may be needed to get a clearer answer.
Tracking your spotting before the appointment helps. Note when it started, whether it’s constant or comes and goes, what color it is, and whether anything seems to trigger it. That information narrows the list of possibilities considerably.