What happens if you leave a hematoma untreated? Your guide to risks and complications

September 29, 2025 •

4 min read

While many small hematomas, or collections of blood, are reabsorbed by the body, an estimated 6.5% of people with subdural hematomas eventually require surgical drainage. The consequences of ignoring a more serious hematoma can be severe, so understanding what happens if you leave a hematoma untreated is critical for your health.

Quick Summary

Leaving a significant hematoma untreated can result in dangerous complications depending on its location, including brain damage from pressure, severe infection, or permanent tissue damage. Even seemingly minor issues can lead to chronic pain and restricted movement if ignored.

Key Points

Location Matters: The risks of an untreated hematoma are most severe in the brain, where pooled blood can cause dangerous pressure, brain damage, coma, and death.
Risk of Infection: Any significant hematoma, especially if large or deep, can become a breeding ground for bacteria, leading to a localized abscess or more serious systemic infection.
Permanent Tissue Damage: Untreated hematomas in confined areas like muscles can lead to restricted movement, chronic pain from scar tissue, or conditions like myositis ossificans.
Nerve and Pressure Damage: Expanding hematomas can compress surrounding nerves and vital structures, causing numbness, weakness, pain, and impaired function.
Urgent Intervention: Unlike a minor bruise that heals quickly, large or deep hematomas may require medical drainage or other interventions to prevent serious complications.

Hematoma vs. Bruise: An Important Distinction

While a common bruise, or contusion, is caused by bleeding from small capillaries near the skin's surface, a hematoma involves larger, clotted collections of blood. This difference is crucial, as the severity and potential complications vary significantly. A bruise typically fades and resolves on its own within a couple of weeks, but a hematoma creates a firm, often painful, and raised lump that poses a greater risk. The danger increases when the hematoma occurs in a confined space, such as the skull or a muscle compartment, where the accumulated blood can exert damaging pressure on surrounding tissues and organs.

The Risks of Ignoring Intracranial Hematomas

Intracranial hematomas, which occur inside the skull, are among the most dangerous to leave untreated and require immediate medical attention. The enclosed space within the skull allows no room for expansion, meaning any accumulation of blood directly increases pressure on the delicate brain tissue.

Subdural Hematoma

Acute Subdural Hematoma: Often the result of severe head trauma, this involves rapid bleeding that can quickly compress the brain, leading to permanent brain damage, coma, or death if not promptly drained.
Chronic Subdural Hematoma: Seen more frequently in older adults or those on blood thinners, this involves slower bleeding that can go unnoticed for weeks. Untreated, the swelling gradually worsens, causing neurological symptoms like confusion, severe headaches, and speech problems.

Epidural Hematoma

Typically caused by a skull fracture tearing an artery, this type involves rapid, high-pressure bleeding. A person may initially regain consciousness after the injury (the 'lucid interval') before a rapid decline as pressure builds. Left untreated, it can lead to seizures, breathing problems, and death.

Complications of Untreated Muscular and Other Hematomas

While less immediately life-threatening than intracranial bleeds, hematomas in other parts of the body can still cause significant and long-lasting problems if left untreated.

Muscular Hematomas

Restricted Mobility and Chronic Pain: A large hematoma within a muscle can limit range of motion and cause persistent pain. Without proper healing, the affected muscle may develop scar tissue (fibrosis), leading to long-term stiffness.
Myositis Ossificans: In some cases, an untreated intramuscular hematoma can lead to a condition where bone tissue forms within the muscle. This causes significant pain and a permanent, hard mass that limits muscle function.
Compartment Syndrome: This is a serious condition that can occur when a large hematoma increases pressure within a muscle compartment in the limbs. The pressure can restrict blood flow, damaging nerves and muscle tissue. Urgent surgical drainage is required to prevent permanent damage.

Auricular and Septal Hematomas

Auricular Hematoma (Ear): If left undrained, blood collecting in the ear cartilage disrupts its blood supply, leading to tissue death (necrosis) and deformity known as 'cauliflower ear'.
Nasal Septal Hematoma: Blood collecting in the nose can cut off blood flow to the septum. This can lead to a dangerous infection (abscess), tissue necrosis, and even sepsis if it ruptures.

General Risks of Any Untreated Hematoma

Regardless of location, there are several general complications associated with leaving any significant hematoma untreated.

Infection: The pooled blood within a hematoma creates an ideal environment for bacteria to grow. This can lead to an infection that turns into an abscess, or in severe cases, a systemic infection or sepsis.
Chronic Hematoma and Encapsulation: A long-standing hematoma can become encapsulated by fibrous tissue, forming a hard mass that the body cannot easily reabsorb. This can result in persistent pain, pressure, and cosmetic concerns that require surgical removal.
Nerve and Tissue Damage: Expanding hematomas can press on nearby nerves, causing symptoms like numbness, tingling, or weakness. They can also damage surrounding blood vessels, impairing circulation.

Comparison: Untreated Hematoma vs. Minor Bruise


Feature	Minor Bruise (Contusion)	Significant Hematoma (Untreated)
Cause	Small capillaries broken, typically superficial	Larger blood vessels torn, can be deep
Appearance	Flat, discolored area; changes color over time	Raised, firm, and often painful lump
Healing Time	Resolves within a few weeks with no intervention	Can persist for weeks or months, may not resolve
Infection Risk	Very low	Elevated risk, especially if large or deep
Pressure on Organs	None	High risk if in confined areas (e.g., skull, muscle)
Long-Term Damage	Minimal to none	Potential for permanent nerve, tissue, or brain damage
Treatment	Usually responds to RICE method	May require surgical drainage or other intervention

Conclusion: Seek Medical Advice When in Doubt

The ultimate risk of an untreated hematoma is dependent on its location, size, and underlying cause. While many minor superficial hematomas will resolve on their own, the potential for serious or even life-threatening complications should not be underestimated. This is especially true for any hematoma resulting from a head injury, which should always be evaluated by a healthcare professional immediately. For concerning symptoms like increasing pain, swelling, or neurological changes, seeking prompt medical evaluation is the best course of action to ensure a favorable outcome. You can learn more about when to seek medical help for a hematoma from reliable health sources like the Cleveland Clinic.

Frequently Asked Questions

A hematoma may be serious if it is located on the head, is growing in size, causes severe or increasing pain, restricts movement, or is accompanied by neurological symptoms like confusion, weakness, or vision changes. Any signs of infection, such as fever, warmth, or pus, also warrant immediate medical attention.

Yes, many minor and superficial hematomas are gradually reabsorbed by the body and go away on their own over several weeks. However, this is not a guarantee, and larger or deeper hematomas, especially in critical areas, often require medical intervention to prevent complications.

A bruise (contusion) is a discoloration from leaked blood from small, damaged capillaries near the skin's surface. A hematoma is a larger, clotted collection of blood, often from a larger vessel, that forms a raised, firm lump.

Yes, an untreated hematoma is at risk of infection. The pooled blood provides a nutrient-rich environment for bacteria, which can lead to a local abscess or, if left unchecked, a more widespread and potentially life-threatening infection.

An untreated hematoma in the leg can lead to chronic pain, restricted mobility from scar tissue, or nerve damage from pressure. In severe cases, a large leg hematoma can lead to compartment syndrome, a medical emergency requiring urgent drainage to prevent permanent muscle and nerve damage.

Long-term consequences vary by location. In the brain, they can include permanent neurological deficits, memory loss, and seizures. In muscles or limbs, they can cause chronic pain, stiffness, or a hardened mass due to fibrosis. The risk of recurrence is also higher, especially for older adults with chronic subdural hematomas.

Dangerous hematomas are treated based on their location and severity. Treatments can range from needle aspiration to drain the blood to open surgical drainage. In cases involving the brain or other vital organs, emergency surgery may be necessary to relieve life-threatening pressure.