A hemorrhage is a loss of blood from the cardiovascular system. It can happen inside the body, where blood pools in tissues or organs, or outside the body through a wound or natural opening. The severity ranges from minor (a small cut) to life-threatening (major internal bleeding), depending on how much blood is lost and how quickly.
External vs. Internal Hemorrhage
External hemorrhage is bleeding you can see. Blood flows from a cut, scrape, surgical site, or body opening like the nose or mouth. Because it’s visible, it’s usually identified and treated quickly.
Internal hemorrhage is harder to detect. Blood leaks from damaged vessels but stays trapped inside the body, collecting in the chest, abdomen, skull, or around joints. Symptoms depend on where the bleeding occurs:
- Head: Sudden severe headache, vision changes, confusion, weakness on one side of the body
- Chest: Difficulty breathing, chest pain, coughing up blood
- Abdomen: Swelling or fullness, bruising on the belly, blood in vomit, urine, or stool
- Bones, joints, and muscles: Bruising, swelling, and pain at the site
Internal bleeding can progress without obvious outward signs. When it becomes severe, it may cause confusion, pale or cold skin, a fast heart rate, sweating, seizures, or loss of consciousness. These are signs of shock, meaning the body is no longer circulating enough blood to keep organs functioning.
Common Causes
Traumatic injury is the most straightforward cause. Car accidents, falls, stab wounds, and blunt force can rupture blood vessels anywhere in the body. But hemorrhage also happens without trauma. Stomach ulcers can erode into a blood vessel and bleed into the digestive tract. An aneurysm, a weakened balloon-like bulge in an artery, can burst in the brain or abdomen. Uncontrolled high blood pressure is the most common driver of spontaneous bleeding inside the brain.
Clotting disorders, whether inherited or caused by blood-thinning medications, make it harder for the body to seal off damaged vessels. Liver disease, certain cancers, and complications during surgery or childbirth are other well-known triggers. Sometimes multiple factors overlap: a person on blood thinners who takes a fall faces a higher risk of dangerous internal bleeding than someone with normal clotting.
How Severity Is Classified
The average adult has roughly 5 liters of blood. Medical teams classify hemorrhage into four levels based on how much of that total volume has been lost:
- Class 1: Up to 15% lost (about 750 mL). Heart rate and blood pressure stay roughly normal. The body compensates well at this stage.
- Class 2: 15% to 30% lost (750 to 1,500 mL). Heart rate rises noticeably, and the person may feel anxious or restless.
- Class 3: 30% to 40% lost (1,500 to 2,000 mL). Blood pressure drops significantly, mental status changes, and the body struggles to keep up. This is a medical emergency.
- Class 4: Over 40% lost. Blood pressure plummets, the heart races above 120 beats per minute, urine output stops, and consciousness fades. Without immediate intervention, this stage is often fatal.
Brain Hemorrhages
Bleeding inside the skull deserves special attention because even small amounts of blood can compress brain tissue in an enclosed space. There are four main types, distinguished by where the blood collects.
An epidural hemorrhage pools between the skull and its outermost protective layer. It’s typically caused by a head injury that tears an artery near the temple. The classic pattern is a brief loss of consciousness after impact, followed by a period of seeming normalcy (a “lucid interval”), and then rapid deterioration as pressure builds.
A subdural hemorrhage collects just beneath that outer layer. It can develop quickly after trauma or slowly over weeks, especially in older adults. Chronic cases may cause gradual personality changes, confusion, or worsening headaches that don’t seem connected to the original injury.
A subarachnoid hemorrhage bleeds into the fluid-filled space surrounding the brain. Its hallmark is a “thunderclap headache,” often described as the worst headache of a person’s life, reaching maximum intensity within seconds. Ruptured aneurysms are the most common cause.
An intraparenchymal hemorrhage bleeds directly into brain tissue. High blood pressure is the leading cause, and it typically presents with sudden stroke-like symptoms: slurred speech, weakness, dizziness, or loss of coordination.
How Hemorrhage Is Diagnosed
When internal bleeding is suspected, speed matters. In emergency rooms, a bedside ultrasound exam called eFAST (Extended Focused Assessment with Sonography in Trauma) is used at more than 96% of major trauma centers. It takes just minutes and can detect free fluid in the abdomen, chest, and the sac around the heart. The advantage is that it happens right at the bedside without moving an unstable patient.
CT scans remain the gold standard for pinpointing the exact location and extent of bleeding. They can detect as little as 100 mL of fluid in the abdomen and are especially critical for identifying brain hemorrhages. Blood work measuring clotting ability and hemoglobin levels helps the team understand how much blood has been lost and whether the body can form clots effectively.
First Aid for External Bleeding
For visible bleeding, the first step is direct pressure. Press firmly on the wound with a clean cloth or gauze, keeping the injured area supported against a solid surface. Don’t lift the cloth to check whether bleeding has stopped, as this disrupts clot formation. Hold steady pressure continuously.
If direct pressure alone isn’t enough, pack the wound cavity with gauze, feeding material in with one hand while keeping pressure with the other. A tight pressure dressing wrapped around the packing can then free your hands.
Tourniquets are appropriate for severe limb bleeding that won’t stop with pressure. They work by squeezing the entire limb tightly enough to compress the artery upstream of the wound. Place the tourniquet a few inches above the bleeding site, tighten until the bleeding stops, and note the time it was applied. Tourniquets are now widely recommended in emergency guidelines after decades of proven battlefield and civilian use.
What Happens if Bleeding Isn’t Controlled
When enough blood is lost, the heart can no longer pump effectively. This is hypovolemic shock, and it can cause organs to shut down. The kidneys are particularly vulnerable, sometimes requiring dialysis temporarily or permanently. The brain, starved of oxygen, can suffer lasting damage. In the most extreme cases, tissue in the arms or legs dies from lack of blood flow, potentially requiring amputation.
Outcomes depend on how much blood was lost, how fast it happened, and how quickly treatment began. People with mild to moderate blood loss who receive timely care generally recover well. Severe shock, especially in older adults or people with existing heart, lung, or kidney disease, carries a much higher risk of lasting complications or death.
Hospital Treatment
Stopping the source of bleeding is the priority. For surgical bleeding, that means techniques like cauterizing damaged vessels with electrical current, tying off torn arteries with stitches, or applying specialized clotting agents directly to a wound surface. These topical agents are used as a backup to standard surgical methods, not a replacement for them.
For internal bleeding that can’t be reached surgically, doctors sometimes thread a catheter through blood vessels to the bleeding site and block it off from the inside, a procedure called embolization. Blood transfusions replace lost volume, and fluids help maintain blood pressure while the source is addressed. In brain hemorrhages, surgery may be needed to drain pooled blood and relieve pressure on the brain.