Blood Clots During Your Period — When to Worry

Blood clots during your period are your body's natural response to heavy flow. When menstrual blood accumulates in the uterus faster than your body's anticoagulants can keep it liquid, it begins to clot — the same way blood clots when you cut your finger, just with different tissue.

Your body releases anticoagulant enzymes to keep menstrual blood flowing smoothly. On heavier days (usually days 1-2), the flow can outpace these enzymes, resulting in visible clots. Clots may also form overnight when blood pools in the uterus while you're lying down, which is why you might notice larger clots first thing in the morning.

The color of clots matters less than their size. They can range from bright red to dark burgundy to almost black, and all of these colors are normal — darker clots have simply been in contact with air longer.

Clots smaller than a quarter (roughly 2.5 cm or 1 inch) are generally considered normal. Think of the size benchmarks this way: pea-sized to grape-sized clots on your heaviest days are common and not a cause for concern.

Consistently passing clots larger than a quarter — especially multiple times per cycle — may indicate menorrhagia (abnormally heavy menstrual bleeding). This distinction matters because chronically heavy bleeding is the most common cause of iron deficiency in women of reproductive age, affecting an estimated 5% of women.

If you're unsure about your clot size, a practical approach is to photograph them (yes, really) over 2-3 cycles so you can show your doctor exactly what you're experiencing. This visual record is far more useful than trying to describe them from memory during an appointment.

Heavy periods with frequent large clots can be a symptom of several treatable conditions. The most common include uterine fibroids (noncancerous growths in the uterus, affecting up to 80% of women by age 50), endometriosis (tissue similar to the uterine lining growing outside the uterus), adenomyosis (uterine lining growing into the muscular wall of the uterus), and bleeding disorders like von Willebrand disease (which affects roughly 1 in 100 women).

Polycystic ovary syndrome (PCOS) can also cause heavy, irregular bleeding when periods do occur. Thyroid disorders and certain medications (including blood thinners and some IUDs during the adjustment period) can contribute as well.

The key is pattern recognition. If your periods have always been moderately heavy with occasional small clots, that's likely your normal. If something has changed — clots are getting bigger, flow is getting heavier, or periods are lasting longer — that's worth investigating.

The clinical definition of heavy menstrual bleeding (menorrhagia) is losing more than 80ml of blood per cycle, but since nobody measures that at home, here are practical signs that your flow is heavier than normal.

Red flags for excessive bleeding include: soaking through a pad or tampon every hour for several consecutive hours, needing to use double protection (pad plus tampon), waking up to change pads or tampons during the night, passing large clots (bigger than a quarter) regularly, and periods that last longer than 7 days.

Physical symptoms of blood loss to watch for include persistent fatigue, shortness of breath during normal activities, dizziness or lightheadedness, pale skin, and cold hands and feet. These can indicate iron deficiency anemia, which develops when blood loss exceeds your body's ability to replenish iron stores.

If you experience these symptoms, ask your doctor to check your complete blood count (CBC) and ferritin levels. Ferritin is particularly important because it drops before your hemoglobin does — you can be iron-depleted before you're technically anemic.

While diet alone won't cure a heavy period, certain nutritional strategies can support your body during menstruation and help manage symptoms. Iron-rich foods are essential if you have heavy periods — prioritize red meat, spinach, lentils, fortified cereals, and pair plant-based iron sources with vitamin C (like lemon juice on spinach) to boost absorption.

Anti-inflammatory foods may help reduce the severity of bleeding. Omega-3 fatty acids (found in salmon, sardines, walnuts, and flaxseed) can help modulate prostaglandin production, which influences both cramps and flow. Turmeric, ginger, and berries also have anti-inflammatory properties.

Some research suggests that magnesium (200-400mg daily) and vitamin B6 may help with PMS and period symptoms overall. Iron supplements may be necessary if blood tests show low ferritin — your doctor can advise on the right dose. Avoid taking iron with calcium, coffee, or tea, which reduce absorption.

One important note: if your heavy bleeding is caused by an underlying condition like fibroids or a bleeding disorder, dietary changes are supplementary — you'll still need medical treatment to address the root cause.

Yes, your period — including clotting patterns — can change throughout your reproductive years. In your teens and early 20s, cycles are often irregular as your hormonal system matures, and you may experience variable flow with occasional clots. In your 20s and 30s, most women establish a predictable pattern.

In your late 30s and 40s, perimenopause begins to shift the landscape. Estrogen fluctuations can cause cycles to become heavier before they taper off. Many women in perimenopause experience their heaviest periods ever, with larger and more frequent clots. This happens because estrogen can spike to higher-than-normal levels (causing the uterine lining to thicken more than usual) before eventually declining.

After menopause (12 consecutive months without a period), any vaginal bleeding — including small clots — is abnormal and requires prompt medical evaluation. While the cause is often benign (vaginal atrophy, polyps), post-menopausal bleeding must be investigated to rule out endometrial cancer.