Do Hematomas Cause Blood Clots? Unpacking the Key Differences

September 23, 2025 •

4 min read

A hematoma is a localized collection of blood outside of blood vessels, often forming a noticeable lump or a deep bruise. Understanding this fundamental distinction is key to answering the question: do hematomas cause blood clots?

Quick Summary

While a hematoma is a pool of blood that has already clotted outside a vessel, it does not directly cause or become a blood clot inside a vein, like a DVT. The processes are distinct, but a severe injury can increase the risk of both occurring independently.

Key Points

Fundamental Distinction: Hematomas are blood clots that form outside a blood vessel, while dangerous blood clots (thrombi) form inside a vessel.
No Direct Causation: A hematoma does not directly cause or turn into a blood clot like a deep vein thrombosis (DVT).
Common Trigger: A severe injury or surgery can be a common trigger that leads to both a hematoma and, independently, an increased risk for a DVT.
Risk of Compression: In rare cases, a large, deep hematoma can physically compress a nearby vein, slowing blood flow and increasing the risk of a DVT.
When to Seek Care: While most hematomas resolve with home care, a growing lump, severe pain, or symptoms of DVT (like unexplained swelling and warmth) require medical evaluation.
Different Dangers: A hematoma's main risks involve local pressure and pain, whereas a DVT can lead to a life-threatening pulmonary embolism (PE) if the clot travels to the lungs.

What is a Hematoma?

At its core, a hematoma is a bad bruise. It occurs when an injury, such as a fall or impact, causes a blood vessel to rupture, and blood leaks out into the surrounding tissue. This pooling of blood, which can be small or large, is what creates the characteristic swollen, discolored lump. A hematoma can form anywhere in the body, from just under the skin (subcutaneous hematoma) to deeper within muscles or organs. The body’s natural response is to wall off this leaked blood, forming a clotted mass that is separate from the circulatory system. Over time, the body reabsorbs this clotted blood, causing the bruise to change color and eventually disappear.

The Real Difference: Hematomas vs. Blood Clots

It is a common misconception that hematomas and blood clots are the same, or that one can transform into the other. A blood clot, or thrombus, is specifically a semi-solid mass that forms inside a blood vessel. This is a critical distinction. A hematoma is blood outside the vessel, while a blood clot is blood inside the vessel. When a blood vessel is damaged, the body's normal clotting response creates a clot at the site of the injury to stop the bleeding. When this happens inside a vessel, it is usually a beneficial, natural process. However, if a clot forms abnormally inside a deep vein, it is called deep vein thrombosis (DVT). This poses a significant danger because it can block blood flow and potentially dislodge, traveling to the lungs and causing a life-threatening pulmonary embolism (PE). Hematomas, conversely, do not carry this same risk of dislodging and traveling through the bloodstream.

The Connection Between Injury, Hematomas, and Blood Clots

While a hematoma does not turn into a blood clot, a severe injury or medical event can increase the risk of both. For instance, a major trauma can lead to both a large hematoma and damage to a nearby deep vein, which could then form a DVT. A primary risk factor for developing DVT is prolonged immobilization, which often follows a significant injury or surgery that might also cause hematoma formation. In these cases, the injury is the common cause, not a causal link between the hematoma and the blood clot. Another, though rare, instance is a large hematoma physically compressing a nearby vein, which can slow blood flow and increase the risk of DVT. However, this is due to external pressure, not the hematoma itself becoming a traveling clot.

Recognizing the Symptoms

Distinguishing between a standard hematoma and a dangerous blood clot like DVT is crucial for your health. While a hematoma's symptoms are typically contained to the site of the injury, DVT can present with different and more severe signs. It's important to be aware of what to look for.

Hematoma Symptoms

Pain and tenderness at the injury site
Swelling or a firm, rubbery lump
Skin discoloration (bruising) that evolves over time
May feel warm to the touch

Deep Vein Thrombosis (DVT) Symptoms

Swelling in one leg or arm
Pain or tenderness, often described as cramping or soreness
Warmth in the affected limb
Changes in skin color, such as redness or purple discoloration
A pulmonary embolism (PE), a medical emergency, can cause shortness of breath, chest pain, and a rapid heartbeat.

When to See a Doctor

Most minor hematomas resolve on their own, but certain signs warrant immediate medical attention. If you have any reason to suspect a DVT or PE, do not delay seeking help.

For a hematoma:
- The bruise or lump grows significantly larger.
- Pain becomes severe or unmanageable.
- You suspect an infection (fever, red streaks, pus).
- The bruise doesn't fade after four weeks.
- You experience neurological symptoms after a head injury.
For a DVT or PE:
- Sudden swelling in one limb.
- Unexplained leg or arm pain.
- Difficulty breathing, chest pain, or rapid heartbeat.

Comparison Table: Hematoma vs. Blood Clot


Feature	Hematoma	Blood Clot (Thrombus)
Location	Outside a blood vessel, in surrounding tissue.	Inside a blood vessel, restricting blood flow.
Formation Cause	Result of a vessel rupturing due to trauma or injury.	Can be a normal part of healing or an abnormal, pathological formation.
Appearance	Often a visible, swollen, discolored lump or bruise.	Often not visible, but can cause swelling, warmth, and pain in the affected area.
Health Risk	Minor ones usually resolve on their own; large or internal ones can cause pressure on organs.	Can lead to serious complications like deep vein thrombosis (DVT) or pulmonary embolism (PE).
Movement	Does not travel through the bloodstream.	Can break free and travel to the lungs, causing a PE.

Conclusion

In summary, the key difference lies in location: a hematoma is clotted blood outside of a vessel, while a blood clot (thrombus) is inside. A hematoma does not directly transform into a dangerous blood clot, and most superficial hematomas are not cause for serious concern. However, severe trauma, surgery, and prolonged immobility can be associated with an increased risk for both conditions. Understanding this distinction is vital for accurately assessing risk and seeking timely medical care when necessary. For further information on managing medical conditions, consider consulting trusted health resources like the Cleveland Clinic.

Frequently Asked Questions

A bad bruise, or hematoma, is not a cause for a dangerous blood clot inside a vein. However, the same severe trauma that causes a significant bruise can also damage a deeper blood vessel, increasing the risk of a blood clot forming independently.

No, a hematoma and a blood clot (thrombus) are not the same thing. A hematoma is a localized pool of blood outside a blood vessel, whereas a blood clot forms inside a vessel.

A hematoma itself does not become a DVT. However, a very large, deep hematoma could potentially compress a nearby vein, slowing blood flow and increasing the risk of DVT. It is important to monitor for signs of DVT, especially after a major injury.

A hematoma is typically a visible lump or deep bruise with localized swelling and discoloration. A deep blood clot (DVT) may not be visible but can cause pain, swelling, warmth, and redness in the affected limb, often in the calf.

Most minor hematomas can be treated with R.I.C.E. (Rest, Ice, Compression, and Elevation). For a large or internal hematoma, or if complications arise, a doctor may need to drain the blood.

Seek medical attention if a hematoma grows larger, becomes increasingly painful, or shows signs of infection like fever or pus. Also, any head injury with neurological symptoms requires immediate care.

Yes, people on blood-thinning medication are at a higher risk of bleeding from minor injuries, which can cause hematomas to form more easily or be larger. They should consult their doctor if they develop a significant hematoma.