A hemorrhage is a loss of blood from a damaged blood vessel. It can happen on the surface of the body, where you can see it, or deep inside organs and tissues where it’s invisible but just as dangerous. The severity ranges from a minor nosebleed to life-threatening internal bleeding that requires emergency surgery. Understanding the differences matters because how a hemorrhage presents, where it occurs, and how much blood is lost all determine what happens next.
External vs. Internal Hemorrhage
External hemorrhage is bleeding you can see: a cut, a puncture wound, or a scalp laceration. The source is usually obvious, and the bleeding can often be controlled with direct pressure. What makes external bleeding dangerous is the speed and volume of blood loss, particularly from deep wounds near major blood vessels.
Internal hemorrhage is harder to recognize because the blood stays trapped inside the body. The most common visible sign is a bruise, which is simply blood leaking from damaged vessels under the skin. But internal bleeding can also occur in places you can’t see at all, like the abdomen, chest, or skull. Even without visible signs, you’ll typically feel something is wrong. Symptoms depend on where the bleeding is happening:
- Head: Sudden severe headache, vision changes, confusion, weakness on one side of the body
- Chest: Difficulty breathing, chest pain, coughing up blood
- Abdomen: Swelling, a feeling of fullness, bruising across the belly, or blood in vomit, urine, or stool
- Muscles and joints: Deep bruising, swelling, and intense pain
General warning signs across all types include weakness, lightheadedness, and pain at the site of bleeding. The severity of symptoms tracks with how much blood has been lost and how quickly.
Common Causes
Trauma is the most straightforward cause. Car accidents, falls, stab wounds, and blunt impacts can rupture blood vessels anywhere in the body. But hemorrhage doesn’t always require an injury. Spontaneous bleeding happens when a blood vessel wall weakens or when the blood itself doesn’t clot properly.
Aneurysms, which are balloon-like bulges in blood vessel walls, account for roughly 85% of spontaneous bleeding in the brain. When an aneurysm ruptures, blood floods the surrounding tissue with no external injury involved. High blood pressure is another major culprit, gradually weakening vessel walls until one gives way. Blood-thinning medications increase the risk of hemorrhage significantly, particularly inside the skull. Even minor head trauma can cause serious bleeding in someone on anticoagulants. Other triggers include blood vessel malformations, clotting disorders, cocaine use, and certain medical procedures.
How Doctors Classify Blood Loss
Not all hemorrhages are equally urgent. The Advanced Trauma Life Support system divides hemorrhagic blood loss into four classes based on how much of the body’s total blood volume has been lost. For a typical adult, total blood volume is roughly 5 liters.
- Class 1 (up to 15%, about 750 mL): Heart rate stays normal or rises slightly. Blood pressure doesn’t change. This is roughly equivalent to donating blood and usually resolves on its own.
- Class 2 (15% to 30%, 750 to 1,500 mL): Heart rate climbs to 100 to 120 beats per minute. Breathing speeds up. Blood pressure may still look normal, but the gap between the upper and lower numbers starts to narrow.
- Class 3 (30% to 40%, 1,500 to 2,000 mL): Blood pressure drops noticeably. Heart rate exceeds 120 beats per minute. Confusion and altered mental status set in. Urine output drops as the body diverts blood to vital organs.
- Class 4 (over 40%, more than 2,000 mL): Dangerously low blood pressure, minimal or no urine output, and a rapidly deteriorating level of consciousness. Without immediate intervention, this stage is fatal.
The earliest signs that blood loss is becoming serious are a rising heart rate, faster breathing, and a narrowing pulse pressure. These changes can appear before blood pressure itself drops, which is why a “normal” blood pressure reading doesn’t always mean the situation is under control.
Bleeding in the Brain
Intracranial hemorrhage is one of the most dangerous forms because the skull leaves no room for expanding blood to go. The pressure builds rapidly, compressing brain tissue and cutting off its blood supply.
There are several types depending on exactly where the blood collects. A subdural hemorrhage occurs when a blood vessel between the brain and skull stretches or tears, usually after a blunt head injury. Subarachnoid hemorrhage involves bleeding into the fluid-filled space surrounding the brain and is most commonly caused by a ruptured aneurysm. Intraparenchymal hemorrhage is bleeding directly into the brain tissue itself, frequently driven by chronic high blood pressure. A non-contrast CT scan of the head is the standard first step for identifying all of these. Fresh blood shows up as a bright white area on the scan.
Bleeding in the Digestive Tract
Gastrointestinal hemorrhage is split into upper and lower based on where the bleeding originates. Upper GI bleeding, from the esophagus, stomach, or upper small intestine, tends to produce vomit that’s bright red or looks like dark coffee grounds. Stool often turns black and tarry because the blood has been partially digested during its trip through the intestines.
Lower GI bleeding, from the colon or rectum, more commonly appears as bright red blood on or mixed with stool. Black, tarry stool can show up with lower GI bleeding too, so the color alone doesn’t always pinpoint the source. Common causes include ulcers, diverticulosis, and inflammatory conditions.
Postpartum Hemorrhage
Hemorrhage after childbirth is defined as cumulative blood loss of 1,000 mL or more, or any blood loss accompanied by signs of low blood volume like dizziness, rapid heart rate, or dropping blood pressure. The older definition set the threshold lower, at 500 mL after vaginal delivery, but the updated criteria focus on clinical impact rather than a fixed number.
The causes are organized around four categories. The most common is poor uterine muscle tone, where the uterus doesn’t contract firmly enough after delivery to compress the blood vessels at the placental site. The other three are physical tears or lacerations during delivery, retained placental tissue or blood clots inside the uterus, and problems with the blood’s ability to clot.
First Aid for External Bleeding
For visible external hemorrhage, the first and most important step is direct pressure. Place your hand firmly on the wound and press. Keep the injured area supported against a solid surface if possible, and don’t release the pressure to check whether the bleeding has stopped. Lifting the dressing resets the clotting process.
If direct pressure alone doesn’t control the bleeding, wound packing can help. This involves filling the wound cavity with gauze, using one hand to feed the material in while the other maintains pressure. Once packed, a pressure dressing, a bulky bandage held tightly in place with a wrap, can free your hands while maintaining compression. For severe bleeding from a limb that won’t respond to these measures, a tourniquet applied above the wound can be lifesaving. For wounds at the junction of the torso and limbs, like the groin or armpit, specialized junctional tourniquets are recommended and should not be delayed even if other methods are being attempted.
How Hemorrhage Is Treated in a Hospital
Once someone with significant hemorrhage reaches a hospital, the priorities are stopping the bleeding and replacing lost blood volume. For internal bleeding that can’t be reached surgically or when surgery would be too invasive, an embolization procedure is a common option. A catheter is threaded through the blood vessels to the site of the bleed, and a substance is injected to block the damaged vessel and stop blood flow through it. This technique works for bleeding from traumatic organ injuries (spleen, liver, lungs), gastrointestinal hemorrhage from ulcers or diverticulosis, tumor-related bleeding, and even severe nosebleeds that won’t respond to simpler treatments.
For hemorrhage with significant blood loss, a medication that helps the body maintain its blood clots can be given intravenously, but it only works within the first three hours after injury. After that window, it becomes less effective and potentially harmful. Surgical options range from tying off or repairing damaged vessels to removing damaged sections of tissue or organs, depending on the source and severity of the bleed.