Period clots are extremely common and usually normal. Your body naturally produces anticoagulants to keep menstrual blood flowing smoothly, but when your flow is heavy, blood can pool in the uterus faster than those anticoagulants can work. The result is clots, typically dark red, jelly-like clumps that show up on your pad or in the toilet. Small clots, around the size of a dime or quarter, are a routine part of menstruation for many people. Clots larger than a quarter, or clots you’re passing every couple of hours, point to something worth investigating.
How Menstrual Clots Form
During your period, the lining of your uterus sheds and exits as a mix of blood, tissue, and mucus. Your body releases natural blood-thinning substances to help this mixture flow out easily. On heavier days, especially the first day or two of your period, the volume of blood can overwhelm that thinning process. Blood sits in the uterus or vagina long enough to coagulate, forming the clumps you see.
This is why clots tend to show up after you’ve been lying down or sitting for a while. Blood pools, clots form, and then when you stand up or move, they pass all at once. The color and texture vary. Fresh clots are bright to dark red and feel gel-like. Older blood that’s had more time to oxidize looks darker, sometimes almost brown or black.
Common Reasons for Larger or More Frequent Clots
Hormone Imbalances
Your uterine lining thickens each cycle in response to estrogen, and progesterone helps regulate how thick it gets. When estrogen levels run high relative to progesterone, the lining builds up more than usual. A thicker lining means more tissue and blood to shed, which means heavier flow and more clotting. This imbalance can happen during puberty, perimenopause, with polycystic ovary syndrome (PCOS), or after stopping hormonal birth control. Thyroid disorders can also throw off hormone levels enough to change your bleeding pattern.
Fibroids
Uterine fibroids are noncancerous growths in or on the wall of the uterus. They’re very common, particularly in your 30s and 40s. Fibroids can distort the shape of the uterine cavity, increase the surface area of the lining, and interfere with the uterus’s ability to contract and slow bleeding. The result is often noticeably heavier periods with larger clots. Fibroids range from tiny to grapefruit-sized, and the ones that grow into the uterine cavity tend to cause the most bleeding problems.
Adenomyosis
Adenomyosis happens when the tissue that normally lines the uterus grows into the muscular wall of the uterus. That displaced tissue still thickens, breaks down, and bleeds with each cycle, but it’s trapped inside the muscle. This makes the uterus enlarge, causes painful cramping, and produces heavy bleeding with clots. It’s most common in people in their 30s and 40s and is sometimes mistaken for fibroids because the symptoms overlap significantly.
Polyps
Endometrial polyps are small, soft growths on the uterine lining. They’re usually benign but can cause irregular or heavy bleeding between or during periods. Like fibroids, they increase the surface area that bleeds and can contribute to clot formation.
What Counts as Heavy Bleeding
It can be hard to judge your own flow objectively, especially if heavy periods have always been your normal. The American College of Obstetricians and Gynecologists considers bleeding “heavy” if any of the following apply:
- Your period lasts longer than 7 days
- You soak through a pad or tampon every hour for several hours in a row
- You need to double up on pads to control the flow
- You have to wake up and change pads or tampons overnight
- You pass blood clots the size of a quarter or larger
Golf ball-sized clots passed every couple of hours are a clear red flag. Even if your periods have “always been like this,” that level of bleeding isn’t something you need to live with. Heavy menstrual bleeding is one of the most common reasons people seek gynecological care, and effective treatments exist.
When Clots Signal a Problem
Persistent heavy clotting can drain your iron stores over time. Your body uses iron to make hemoglobin, the protein in red blood cells that carries oxygen. When you lose more blood than your body can easily replace, iron deficiency anemia develops. The symptoms creep up gradually: fatigue that doesn’t improve with sleep, shortness of breath during normal activities, headaches, dizziness, and feeling cold when others are comfortable. Many people chalk these up to stress or poor sleep without connecting them to their periods.
A sudden change in your bleeding pattern also matters. If your periods have always been light and you’re suddenly passing large clots, or if you’re bleeding heavily between periods, something has shifted. New clotting paired with severe pelvic pain could point to adenomyosis, an ectopic pregnancy, or a miscarriage. Miscarriage tissue tends to look different from normal period clots. At around 8 weeks, it often appears dark red and shiny, sometimes described as looking like liver. At 10 weeks, clots may contain what looks like a membrane. If there’s any chance you could be pregnant and you’re passing unusual tissue, that warrants prompt medical attention.
How Doctors Find the Cause
If you go in for heavy clotting, expect a physical and pelvic exam first. From there, the workup typically includes blood tests to check your hormone levels, thyroid function, blood clotting ability, and a pregnancy test. Your doctor will also check for anemia by looking at your red blood cell count and iron levels.
A pelvic ultrasound is usually the first imaging step. A transvaginal ultrasound, where a small wand is inserted vaginally, gives a detailed picture of the uterine lining, the uterine wall, and the ovaries. This is how most fibroids and some cases of adenomyosis are spotted. If more detail is needed, sonohysterography (where saline is injected into the uterus before the ultrasound) helps outline polyps or fibroids that sit inside the cavity. An MRI is occasionally used for a more detailed look. Hysteroscopy, a procedure where a thin, lighted scope is passed through the cervix, lets your doctor see the inside of the uterus directly and can even remove polyps at the same time. An endometrial biopsy, a small tissue sample from the lining, may be taken to rule out abnormal cell changes.
Treatments That Reduce Clotting
Treatment depends on what’s causing the heavy bleeding, but most options aim to either reduce the thickness of your uterine lining, slow down bleeding, or address the structural problem directly.
Hormonal birth control (pills, hormonal IUDs, patches, or injections) thins the uterine lining over time, which typically reduces both flow volume and clot size. A hormonal IUD is one of the most effective options and works locally in the uterus with minimal systemic hormone exposure. For people who can’t or don’t want to use hormonal methods, a medication that prevents blood clots from breaking down too quickly can be taken during your period. This type of medication is designed to be used only during heavy bleeding days, and if it hasn’t made a noticeable difference after two cycles, it’s worth revisiting with your doctor.
When fibroids or polyps are causing the problem, procedures to remove them often resolve heavy bleeding. Options range from minimally invasive removal through a hysteroscope to procedures that shrink fibroids by cutting off their blood supply. For adenomyosis, hormonal treatments are the first line, with surgical options reserved for severe cases.
Tracking your cycle for a couple of months before your appointment helps. Note how many pads or tampons you use per day, how often you change them, and whether you see clots. Snap a photo if you pass something large. This kind of detail gives your doctor a much clearer picture than “my periods are heavy” alone.