What are the side effects of a hematoma?

September 29, 2025 •

5 min read

While most people associate a hematoma with a common bruise, this collection of blood can cause a range of side effects depending on its size and location. What are the side effects of a hematoma and when should you be concerned about this condition?

Quick Summary

A hematoma can cause side effects ranging from minor bruising and swelling to serious complications like nerve damage or brain pressure, with symptoms like discoloration, pain, and confusion depending on its location within the body.

Key Points

Common Side Effects: Pain, swelling, and a distinct, color-changing lump or bruise are the most common side effects, varying in severity with size and location.
Life-Threatening Risks: Hematomas in critical areas like the brain can cause severe headaches, confusion, seizures, or paralysis due to pressure on neurological tissues.
Dangerous Internal Complications: Abdominal hematomas or those causing compartment syndrome can lead to internal bleeding, nerve damage, or tissue death, requiring immediate medical intervention.
Long-Term Consequences: If not properly treated, a hematoma can lead to infection, permanent scarring, or stiffness, with some cases resulting in bone formation within muscle.
Bruise vs. Hematoma: A hematoma involves more significant bleeding from larger vessels, forming a distinct lump that can be more painful and take longer to heal than a simple bruise.
When to See a Doctor: Seek immediate medical care for rapidly expanding hematomas, severe pain, or neurological symptoms, while monitoring for infections or persistent issues.

Understanding a Hematoma

A hematoma is a localized collection of clotted blood that forms outside of blood vessels, often as a result of trauma or injury. Unlike a simple bruise, which involves minor bleeding from small capillaries, a hematoma typically results from damage to larger blood vessels, causing a more significant pooling of blood. The side effects can vary drastically based on the hematoma's location, size, and whether it is pressing on surrounding tissues or nerves. While many small, superficial hematomas resolve on their own with conservative treatment, larger or deeper ones—especially those in critical areas like the head or abdomen—may require urgent medical attention. Recognizing the different types of side effects and knowing when to see a healthcare professional is crucial for managing this condition effectively.

Common and Localized Side Effects

The most frequent side effects of a hematoma are localized to the site of the injury. These are often seen in subcutaneous (under the skin) or intramuscular (within the muscle) hematomas.

Visible Bruising and Discoloration: As the pooled blood begins to clot and break down, the skin over the hematoma will change color. This color progression typically moves from red or purplish-blue to green, and finally to a brownish-yellow before fading completely.
Swelling and Tenderness: The buildup of blood can cause a noticeable lump or swelling, which is often tender and painful to the touch. This swelling is a natural inflammatory response as the body works to heal the area.
Pain: The trapped blood puts pressure on the surrounding nerves and tissues, which can cause mild to significant pain depending on the size and location.
Restricted Movement: If a hematoma is located in or near a joint or a large muscle, the associated swelling and pain can limit your range of motion.

Serious Side Effects by Location

While superficial hematomas are often harmless, those in more sensitive areas can lead to severe, and sometimes life-threatening, side effects.

Intracranial (Brain) Hematomas

These are among the most dangerous types, as they can cause pressure on the brain. They include subdural and epidural hematomas.

Severe Headache: Often described as sudden and intense.
Confusion or Lethargy: A change in mental status, from mild confusion to unconsciousness.
Nausea and Vomiting: Caused by increased intracranial pressure.
Neurological Deficits: Weakness or paralysis, especially on one side of the body.
Vision Problems: Blurred or double vision, or unequal pupil sizes.
Seizures: Sudden, uncontrolled electrical activity in the brain.
Slurred Speech: Difficulty speaking clearly.

Abdominal Hematomas

Hematomas in the abdomen or surrounding organs can cause internal bleeding and put pressure on vital structures.

Severe Abdominal or Flank Pain: Localized to the area of the bleeding.
Low Blood Pressure: Signs of internal bleeding, including dizziness, lightheadedness, or pale skin.
Distended Abdomen: Bloating or swelling of the abdominal area.

Intramuscular (Compartment Syndrome)

This is a critical emergency where a hematoma in a muscle is constrained by tough fascia, causing a dangerous buildup of pressure.

Pain Out of Proportion to the Injury: The pain is intense and worsens with movement.
Numbness or Tingling: Pins-and-needles sensation due to nerve compression.
Weakness and Pale Skin: Impaired blood flow can lead to muscle weakness and a pale appearance.

Subungual (Under the Nail) Hematomas

Caused by crush injuries, this type of hematoma is extremely painful due to pressure.

Intense Throbbing Pain: The pressure of the blood under the nail is severe.
Discoloration of the Nail: The nail will turn dark blue or black.

Hematoma vs. Bruise: A Comparison

It is important to differentiate a hematoma from a simple bruise, as their side effects and necessary treatment can differ significantly.


Feature	Hematoma	Bruise (Contusion)
Cause	Trauma to larger blood vessels, causing a significant pooling of blood.	Damage to small capillaries, causing minor bleeding under the skin.
Appearance	Often a raised, firm, and tender lump.	A flat, discolored area on the skin.
Pain Level	Can range from mild to severe, often more painful due to pressure.	Typically mild to moderate pain.
Healing Time	Weeks to months, depending on size and location.	Usually resolves within 1-2 weeks.
Location	Can occur anywhere in the body, including internal organs.	Typically occurs in superficial layers of the skin.
Severity	Can be serious or life-threatening if located in critical areas.	Rarely serious, unless associated with another injury.

The Healing Process and Potential Long-Term Side Effects

As the body naturally reabsorbs the blood from a hematoma, the swelling and discoloration will subside over several weeks or months. However, sometimes the healing process can lead to other issues.

Infection: A hematoma creates a perfect breeding ground for bacteria. If bacteria enter the site, it can lead to an infection, abscess, or even sepsis. Signs include increased redness, warmth, pain, and fever.
Fibrosis and Scarring: For larger or prolonged hematomas, the body can deposit fibrous tissue during healing, leading to permanent stiffness or a hardened lump at the site.
Myositis Ossificans: A rare complication where calcium deposits lead to bone formation within the muscle, causing pain and restricted movement.
Recurrence: Some individuals may be prone to recurrent hematomas, especially if they have underlying clotting disorders.
Permanent Neurological Damage: Severe intracranial hematomas, if not treated promptly, can lead to lasting brain damage, seizures, or cognitive issues.

When to Seek Medical Attention

While many small hematomas can be managed at home, it is crucial to recognize the signs that require professional medical care. For additional information on different types of hematomas and treatment, you can refer to the detailed resources provided by the Cleveland Clinic.

Seek immediate medical attention if you experience:

A rapidly expanding hematoma.
Severe, disproportionate pain.
Signs of an intracranial hematoma (headache, confusion, slurred speech).
Signs of internal bleeding (pale skin, low blood pressure, severe abdominal pain).
Signs of compartment syndrome (tingling, numbness, severe pain in a limb).
Signs of infection (fever, warmth, redness, pus).

Schedule a doctor's visit if:

The hematoma doesn't improve within two weeks.
Bruising is frequent or unexplained.
The hematoma causes persistent or worsening symptoms.

Conclusion

Hematomas are more than just bad bruises, and their side effects can range from mild cosmetic concerns to life-threatening complications. Understanding the signs and symptoms associated with different types of hematomas is the first step toward proper management. For most minor cases, rest, ice, compression, and elevation (R.I.C.E.) will suffice. However, for more severe or deep-seated hematomas, or those accompanied by worrying symptoms, prompt medical evaluation is essential to prevent serious and permanent side effects. Always consult a healthcare provider with any concerns, especially after significant trauma or if you notice any of the red-flag symptoms.

Frequently Asked Questions

The duration of a hematoma's side effects varies depending on its size and location. A small, superficial hematoma may resolve within a couple of weeks, with color changes occurring as it heals. Larger or deeper hematomas can take several months to fully reabsorb and may cause persistent pain or swelling during that time.

Yes, a hematoma can become infected. Because a collection of blood provides an ideal environment for bacteria, an undrained hematoma, especially near an open wound, can develop an infection or an abscess. Signs of infection include increased redness, warmth, swelling, fever, and pus.

Yes, if a hematoma is located near a nerve or causes significant pressure on surrounding tissues, it can lead to nerve compression. This can result in side effects like numbness, tingling, or weakness in the affected area. In severe cases like compartment syndrome, prompt treatment is needed to prevent permanent nerve or tissue damage.

While both involve bleeding under the skin, a bruise (or contusion) is a minor injury to small capillaries, causing flat discoloration. A hematoma involves larger blood vessels and forms a raised, often tender lump of clotted blood. A hematoma is typically more painful and takes longer to heal than a simple bruise.

A healthcare provider may need to drain a hematoma if it is large, causing significant pain, or putting pressure on nerves or other vital structures. Drainage is also necessary if the hematoma shows signs of infection or is located in a critical area like the skull. Not all hematomas require drainage; small ones often resolve on their own.

Yes, in some cases, a hematoma can lead to permanent scarring or a hard mass. This can occur if the blood is not fully reabsorbed and fibrous tissue forms in its place. This can also happen in a rare condition called myositis ossificans, where bone-like material forms within muscle after a hematoma.

A hematoma in or around the brain (intracranial) is very serious and can cause severe side effects due to increased pressure. These include intense headaches, confusion, nausea, vomiting, dizziness, seizures, and weakness or numbness in the limbs or face.

References

1
Hematoma Definition, Types & Treatment - Cleveland Clinic