Ever feel like there's a crime scene in your pants? As the Head of Style & Innovation at Beautikini, and a former competitive swimmer, I've heard every concern imaginable about periods. Let's be direct: we're here to dive deep into everything about menstrual blood clots. What are these little things, are they normal, and when should you talk to a medical professional? Let's untangle it all for you in this complete 2025 guide.
Our bodies are amazing and unique. Every person's menstrual cycle is different, and while that's something to celebrate, it can also lead to questions, especially about menstrual blood and clots. So, what causes period clots, and should you be concerned? Beautikini has compiled this guide to help you accurately understand what's normal and what might not be. Read on for the details.
Key Takeaways
- Clots Are Usually Normal: For most people, passing small menstrual blood clots (smaller than a quarter) is a completely normal part of menstruation, especially during heavy flow days.
- Formation Explained: Clots form when blood pools in the uterus and the body’s natural anticoagulants can't thin it quickly enough before it's expelled.
- When to Seek Advice: If you consistently notice clots larger than a quarter, accompanied by severe pain, or a need to change protection hourly, it's wise to consult a doctor to rule out conditions like fibroids or endometriosis.
What Are Menstrual Blood Clots?
Have you ever noticed thick, jam-like "clots" during your period? These are menstrual blood clots, composed of coagulated blood, tissue, and mucus from the uterine lining.
While they might sound concerning, they are actually a very normal part of the process for most menstruating individuals. In fact, in most cases, these clots indicate that your body is functioning exactly as it should.
They can range in color from bright red to darker hues. Typically, normal clots are usually no larger than a penny or a quarter and don't occur constantly throughout your entire cycle.
What Causes Menstrual Blood Clots?
So, what’s the science behind them? Blood clots occur when menstrual blood accumulates within the uterus, awaiting uterine contractions to expel it from the body.
Our bodies are incredibly smart. They typically release anticoagulants to thin this mixture for easier passage. However, during a heavy flow, blood can exit so rapidly that these anticoagulants can't keep up. When this happens, blood pools and clots form.
This natural clotting mechanism is the same one that stops bleeding when you get a cut. Small cells called platelets and other clotting factors rush to seal off bleeding blood vessels in the uterine lining as it sheds. It's a completely normal biological response, especially in the first two days of menstruation when blood flow is heaviest.
What Do Menstrual Blood Clots Look Like?
The size, thickness, and color of period clots can vary. If you've been tracking your cycle and know what's normal for you (check out our menstrual blood color guide), you may have noticed some clots during your period. Of course, everyone's body is different, so as a general guide, menstrual clots typically fall into one of the following categories:
Normal Menstrual Clots
Normal clots can range in color from bright red to dark red and have a thick, almost jelly-like consistency. They're usually no larger than 2.5 centimeters (about the size of a U.S. quarter) and primarily occur on the heaviest days of bleeding. Tracking your period can help you understand your flow, so you might know when to expect heavier bleeding.
Brown or Black Blood Clots During Menstruation
Seeing brown or even black clots is usually nothing to worry about. This happens when blood is older and has had time to oxidize. They may occur towards the end of your period as blood flow slows down, or sometimes at the very beginning as your body clears out any "old" blood from the previous cycle.
Small Blood Clots During Menstruation
Small clots are generally nothing to worry about. As a general guide, health organizations like the National Health Service (NHS) suggest that clots smaller than a 10-pence coin (similar to a U.S. quarter) are usually not a cause for concern.
Normal vs. Abnormal Blood Clots: When to Pay Attention
While most period clots are entirely normal, it's crucial to understand what abnormal clots might signify. Being able to discern between a normal occurrence and a potential issue empowers you to take charge of your health. Abnormal menstrual blood clots aren't always a cause for alarm, but they can sometimes indicate an underlying issue that needs a doctor's attention.
| Characteristic | Normal Clots | Potentially Abnormal Clots |
|---|---|---|
| Size | Smaller than a U.S. quarter | Consistently larger than a quarter |
| Frequency | Occasional, mainly on heaviest flow days | Very frequent and throughout the period |
| Associated Symptoms | Standard menstrual cramps | Severe pain, fatigue, dizziness, or weakness |
| Flow Volume | Manageable with regular period products | Soaking through a pad/tampon every 1-2 hours |
Here are some conditions that could be underlying causes of excessive menstrual blood clots:
Uterine polyps or fibroids: These non-cancerous growths can block the uterus, preventing it from contracting properly. This slow expulsion of blood allows more time for larger clots to form. They may also cause back pain, pain during intercourse, bloating, and fertility issues.
Endometriosis or adenomyosis: Endometriosis is a major culprit for painful periods and heavy bleeding with clots, as uterine lining tissue grows outside the uterus. Adenomyosis causes similar problems and can also lead to significant menstrual clotting. Research on this topic is extensive, with institutions like the National Institute of Child Health and Human Development offering in-depth information.
Enlarged uterus: After childbirth, for example, the uterus can remain slightly larger, providing more space for blood to accumulate and clot before it's expelled.
Bleeding disorders: Conditions like von Willebrand disease (VWD) can interfere with the blood's ability to clot properly, leading to abnormal or heavy menstrual bleeding.
Miscarriage: Mild bleeding during pregnancy can be common but should always be checked by a doctor. However, heavy bleeding with clots during a known pregnancy is a medical emergency and could be a sign of miscarriage, requiring immediate medical help.
It's also worth noting that consistently passing large clots can lead to other health complications, such as iron-deficiency anemia due to excessive blood loss. Your doctor can help determine if treatment is needed. Heavy bleeding with clots is not something you should just endure, so please seek professional advice.
Using Period Underwear to Manage Blood Clots
One of the biggest complaints I hear from people with a heavy menstrual flow is the frustration of constantly changing sanitary products. Leaking onto underwear or bedding can negatively impact your daily life—not to mention the financial cost!
If this sounds familiar, then reusable period underwear might be the game-changing solution you're looking for. They can completely replace pads and tampons, and many find they can go much longer between changes.
For instance, our Beautikini Period Underwear is designed to hold up to 40ml of fluid, which is equivalent to about 8 regular tampons. This level of absorbency provides serious peace of mind.
If you're dealing with blood clots during your period, a reliable product like Beautikini Period Underwear can truly change the game, allowing you to go about your daily activities stress-free. If you have any questions, my team and I are always here to help!
Frequently Asked Questions
Q1: Are blood clots during my period normal?
Yes, for most individuals, passing small (smaller than a quarter) menstrual clots, especially on the heaviest days of your period, is completely normal. They are a natural part of the menstruation process as the uterus sheds its lining.
Q2: What is the normal size for menstrual blood clots?
Normal menstrual clots are typically no larger than a U.S. quarter (about 2.5 cm or 1 inch in diameter). If you consistently pass clots larger than this, it's a good idea to consult with a healthcare professional.
Q3: Why are my period clots suddenly bigger?
A sudden increase in the size or frequency of clots can be due to various factors, including hormonal changes, lifestyle shifts, or underlying medical conditions like uterine fibroids or endometriosis. While an occasional large clot might not be alarming, a consistent change warrants a discussion with your doctor.
Q4: Can stress cause large blood clots during my period?
Yes, high levels of stress can affect your hormonal balance, which in turn can influence your menstrual cycle. This can sometimes lead to a heavier flow and, consequently, larger or more frequent blood clots. Managing stress may help regulate your cycle.
Q5: How can I manage heavy bleeding with clots?
Managing heavy flow and clots involves using highly absorbent period products. I personally recommend our Beautikini Period Underwear, as it can hold up to 8 tampons' worth of flow, providing leak-proof confidence and comfort without the constant need for changes. This allows you to go about your day without worry.
References
Increased plasma clot permeability and susceptibility to lysis are associated with heavy menstrual bleeding of unknown cause: a case-control study - P Szczepaniak, M Zabczyk, A Undas - PLoS One, 2015
Determinants and assessment of menstrual blood flow - J Liang, F Ali, M Ramaiyer, MA Borahay - Current epidemiology reports, 2023 - Springer
Heavy menstrual bleeding: an update on management - J Davies, RA Kadir - Thrombosis research, 2017 - Elsevier
