Haemorrhage is a loss of blood from damaged blood vessels that can occur inside or outside the body, ranging from minor bruises to life-threatening internal bleeding. Understanding the signs of excessive blood loss and knowing when to seek emergency help can make the difference between recovery and serious complications.

What Is a Haemorrhage?

A haemorrhage occurs when blood escapes from blood vessels due to damage or rupture. This bleeding can happen anywhere in the body, since blood vessels are distributed throughout every organ and tissue. The blood may flow visibly outside the body through a wound or opening, a condition called external haemorrhage. Alternatively, it can remain trapped within the body, known as internal haemorrhage, where it pools in tissues or body cavities without being immediately visible.^[1]

The severity of a haemorrhage depends on multiple factors, including how much blood is lost, how quickly the bleeding occurs, and where in the body it takes place. Minor haemorrhages, such as small bruises under the skin, are common and usually harmless. However, major haemorrhages can quickly become medical emergencies that threaten life if not treated promptly. A related term is hematoma, which describes a pooling of blood in the tissues after vessels are damaged.^[1]

Most haemorrhages require urgent medical attention. The body can naturally compensate for small amounts of blood loss, but when bleeding becomes severe, it can lead to a dangerous condition called hypovolemic shock. This occurs when so much blood is lost that the heart, brain, and other vital organs cannot receive enough oxygen to function properly, potentially resulting in organ failure or death.^[1]

Different Types of Haemorrhage

Haemorrhages are classified based on their location in the body and which type of blood vessel is affected. Understanding these different types helps medical professionals respond appropriately to bleeding emergencies.

The three main blood vessel types that can haemorrhage are arteries, veins, and capillaries. Arteries carry oxygen-rich blood from the heart to the rest of the body under high pressure. Arterial haemorrhage is the most dangerous type because blood loss is rapid and difficult to control. The blood typically appears bright red and may spurt with each heartbeat. Veins carry blood back to the heart at lower pressure, so venous haemorrhage involves a steadier flow of dark red blood that is less severe than arterial bleeding but still requires prompt treatment. Capillary haemorrhage involves the tiniest blood vessels and usually produces slow oozing or trickling of blood, often stopping on its own.^[10]

Specific types of haemorrhage are named according to their location in the body. An intracranial haemorrhage or brain bleed involves bleeding inside the skull or within the brain tissue itself. When bleeding occurs specifically within brain tissue, it may cause a haemorrhagic stroke, which is particularly severe and can worsen rapidly. A subarachnoid haemorrhage occurs in the space between the brain and the thin tissues covering it, typically causing sudden and severe headache.^[1]

In the chest area, a hemothorax describes blood collecting between the lungs and rib cage, which can compress the lungs and make breathing difficult. Gastrointestinal haemorrhages involve bleeding in the digestive system, which may result from ulcers, infections, or certain medications. Postpartum haemorrhage refers to severe vaginal bleeding after childbirth, occurring either immediately after delivery or up to 12 weeks later, and represents a serious complication that can be fatal without proper treatment.^[1][13]

One of the few types of haemorrhage that is usually not serious is subconjunctival haemorrhage, which involves bleeding in the white part of the eye. The blood becomes trapped in the conjunctiva but typically resolves without treatment.^[1]

Epidemiology: How Common Are Haemorrhages?

Haemorrhages represent a significant global health burden, particularly when they result from traumatic injury. Worldwide statistics paint a concerning picture of how frequently severe bleeding contributes to death and disability across different populations and age groups.

Haemorrhage secondary to traumatic injury stands as the leading cause of death among Americans aged 1 to 46 years. This statistic highlights the particular vulnerability of younger populations to fatal bleeding from accidents, violence, and other trauma. In 2015, the National Trauma Institute estimated that severe bleeding accounts for more than 35 percent of deaths occurring before patients reach the hospital, and nearly 40 percent of deaths within the first 24 hours after injury.^[2]

On a global scale, the World Health Organization estimated in 2000 that injuries resulted in 9 percent of worldwide deaths and 12 percent of the global disease burden. Severe trauma causes more than 5 million deaths annually around the world, with projections suggesting this number could surpass 8 million deaths per year. Among these traumatic deaths, haemorrhage accounts for approximately 35 percent of mortality, making it the second leading cause of death from trauma after injuries to the central nervous system. Violence represents the primary cause of these injuries, with traffic collisions ranking second.^[2]

Perhaps most concerning is that up to half of all deaths resulting from haemorrhage occur before the injured person reaches definitive medical care. This statistic underscores the critical importance of rapid intervention and proper first aid in haemorrhage situations. The problem is compounded by the fact that coagulopathy, a condition where blood does not clot properly, affects about 25 percent of injured patients, further increasing their risk of fatal bleeding.^[2]

For specific types of haemorrhage, the frequency varies. Postpartum haemorrhage, for example, affects approximately 1 to 5 percent of all deliveries, with rates differing slightly between vaginal deliveries and caesarean sections. While many of these cases are not life-threatening with prompt treatment, postpartum haemorrhage remains a significant cause of maternal death worldwide.^[13]

Haemorrhagic strokes, caused by bleeding in the brain, make up about 13 percent of all stroke cases. Though less common than strokes caused by blocked blood vessels, haemorrhagic strokes tend to be more severe and have higher mortality rates.^[7]

Causes of Haemorrhage

Haemorrhages can result from a wide variety of causes, ranging from physical trauma to underlying medical conditions that affect the blood vessels or the blood’s ability to clot. Understanding what causes bleeding helps in both prevention and treatment.

Traumatic injury represents one of the most common causes of haemorrhage. Physical trauma can damage blood vessels in multiple ways, leading to bleeding of varying severity. Simple abrasions or scrapes typically affect only capillaries near the skin’s surface and cause minor bleeding. Lacerations, or cuts, may damage deeper vessels and result in more significant blood loss. Puncture wounds from needles, nails, or knives can penetrate deeply and damage important blood vessels. Crushing injuries, where tissue is compressed between two hard surfaces, often cause extensive internal bleeding. Gunshot wounds frequently result in severe haemorrhage because bullets can tear through multiple blood vessels and organs.^[5]

Various medical conditions can cause haemorrhage even without obvious injury. Hemophilia is a genetic disorder where the blood lacks certain clotting factors, specifically Factor VIII in Hemophilia A or Factor IX in Hemophilia B, making it difficult for blood to clot normally. Von Willebrand disease, another inherited bleeding disorder, results from deficiency or dysfunction of the Von Willebrand factor, a protein crucial for platelet function and clotting. Thrombocytopenia describes a condition where the blood contains too few platelets, the cell fragments responsible for forming clots.^[5]

Liver disease can lead to haemorrhage because the liver produces many of the proteins necessary for blood clotting. When the liver is damaged or not functioning properly, it cannot manufacture adequate amounts of these clotting factors. Leukemia and other blood cancers can cause bleeding by disrupting normal blood cell production, including the cells needed for clotting.^[5]

Certain infections can weaken blood vessel walls or interfere with clotting mechanisms, potentially leading to haemorrhage. Brain trauma, whether from accidents or other causes, can result in intracranial bleeding. Conditions affecting specific organs, such as lung cancer, acute bronchitis, or colon diverticolosis, may cause bleeding in those particular areas of the body.^[5]

Some haemorrhages occur spontaneously due to weaknesses in blood vessel walls. An aneurysm is a bulging, weakened area in an artery wall that can rupture and cause sudden, severe bleeding. This is particularly dangerous when it occurs in the brain or major blood vessels like the aorta.^[3]

Risk Factors for Developing Haemorrhage

While anyone can experience a haemorrhage, certain factors increase the likelihood of severe bleeding or make it more difficult to control when it occurs. Recognizing these risk factors helps identify individuals who need extra precautions or monitoring.

People with inherited bleeding disorders face a significantly elevated risk of haemorrhage throughout their lives. Those with hemophilia or Von Willebrand disease must be especially careful to avoid injuries and may require preventive treatment before surgeries or dental procedures. Even minor trauma that would be insignificant in most people can cause prolonged bleeding in individuals with these conditions.^[16]

Taking certain medications substantially increases haemorrhage risk. Individuals on blood-thinning medications such as warfarin, heparin, or newer anticoagulants face higher risks of both external and internal bleeding. This is especially true if the medication dose is not carefully monitored and adjusted. People taking multiple medications that affect clotting, such as combining aspirin with prescription anticoagulants, face even greater risk.^[5]

Chronic medical conditions that affect the liver put people at increased risk because the liver manufactures most clotting factors. Advanced liver disease, cirrhosis, or liver failure can severely impair the blood’s ability to clot, making even minor bleeding difficult to stop. Similarly, individuals with kidney disease may have abnormal platelet function and increased bleeding tendency.^[5]

For postpartum haemorrhage specifically, several pregnancy-related factors increase risk. Placental abruption, where the placenta detaches from the uterus early, can cause severe bleeding. Placenta previa, where the placenta covers or is near the cervical opening, increases bleeding risk during delivery. Women carrying multiples, having too much amniotic fluid, or delivering very large babies face higher risks because the uterus becomes overly stretched and may not contract effectively after delivery to stop bleeding. Previous cesarean sections or uterine surgeries can also increase the risk of postpartum haemorrhage.^[13]

High blood pressure represents a significant risk factor for certain types of haemorrhage, particularly brain bleeds and haemorrhagic stroke. Chronic hypertension weakens blood vessel walls over time, making them more likely to rupture. This is especially dangerous in the brain, where even small amounts of bleeding can cause severe damage.^[1]

Age can influence haemorrhage risk in different ways. Older adults often have more fragile blood vessels and are more likely to be taking medications that affect clotting. They may also have multiple chronic conditions that increase bleeding risk. However, younger individuals face higher rates of traumatic haemorrhage due to accidents, violence, and high-risk activities.^[2]

Lifestyle factors and occupational hazards also play a role. People engaged in contact sports, military service, or occupations with high injury risk face greater exposure to traumatic haemorrhage. Excessive alcohol consumption can damage the liver and interfere with clotting factor production. Vitamin K deficiency, whether from poor diet or certain medical conditions, impairs the body’s ability to produce clotting factors.^[5]

Symptoms of Haemorrhage

The symptoms of haemorrhage vary considerably depending on where the bleeding occurs, how much blood is lost, and how rapidly the blood loss happens. Recognizing these warning signs is crucial for seeking timely medical help.

Healthcare providers classify haemorrhages into four classes based on the percentage of total blood volume lost. A Class I haemorrhage involves loss of up to 15 percent of blood volume. Most people with this level of blood loss do not experience noticeable symptoms because the body can compensate effectively for this amount of blood loss.^[1]

A Class II haemorrhage represents loss of 15 to 30 percent of total blood volume. At this level, symptoms begin to appear as the body struggles to maintain normal function. People may experience dizziness or lightheadedness, particularly when standing up, due to dropping blood pressure. Fatigue and weakness become noticeable. Nausea and vomiting may occur. Breathing becomes faster and more labored, a condition called dyspnea. The heart rate increases, known as tachycardia, as the heart tries to pump the remaining blood faster to maintain adequate circulation.^[1]

When blood loss exceeds 30 percent of total volume, classified as Class III or IV haemorrhage, symptoms become severe and life-threatening. Confusion may develop as the brain receives insufficient oxygen. Some people experience seizures. Loss of consciousness can occur rapidly. The most dangerous complication is hypovolemic shock, where blood pressure drops so low that organs begin to fail from lack of oxygen.^[1]

External haemorrhage is usually easier to recognize because bleeding is visible. Blood flows from a wound or body opening, and the amount and speed of blood loss provide clues to severity. However, it can sometimes be difficult to judge how serious the bleeding is, especially if it comes from a major artery. Arterial bleeding typically produces bright red blood that spurts rhythmically with each heartbeat, while venous bleeding produces darker red blood that flows more steadily.^[10]

Internal haemorrhage presents greater challenges for recognition because the bleeding is not visible. Symptoms depend heavily on the location of bleeding. Brain haemorrhages often cause sudden, severe headache described as the worst headache of one’s life. Vision changes, confusion, weakness or numbness on one side of the body, difficulty speaking, seizures, or loss of consciousness may also occur.^[1]

Bleeding in the chest may cause difficulty breathing, chest pain, and coughing up blood. These symptoms can indicate bleeding in the lungs or blood collecting around the lungs. Abdominal haemorrhages may produce swelling or a feeling of fullness in the belly, visible bruising on the abdomen, or blood appearing in vomit, urine, or stool. The blood in stool may appear bright red or black and tarry, depending on where in the digestive tract the bleeding occurs.^[1]

Bleeding in bones, joints, or muscles causes bruising, swelling, and pain at the affected site. When bleeding occurs in a closed space, such as within a muscle compartment, pressure can build up dangerously. This increased pressure can compress nerves and blood vessels, potentially leading to permanent loss of function if not treated urgently.^[1]

People experiencing internal bleeding may develop pale or clammy skin as blood flow to the skin decreases. Extremities may feel cold to the touch. As bleeding continues, the symptoms of shock become more apparent, including rapid, weak pulse, rapid shallow breathing, and altered mental status.^[5]

Prevention of Haemorrhage

While not all haemorrhages can be prevented, many strategies can reduce the risk of serious bleeding or help detect problems early when they are more treatable. Prevention approaches differ depending on whether the focus is on traumatic or medical causes of haemorrhage.

For preventing traumatic haemorrhage, safety measures play a crucial role. Wearing seatbelts in vehicles significantly reduces the risk of severe injuries in traffic accidents, one of the leading causes of traumatic bleeding. Using appropriate protective equipment during sports, work, or other activities can prevent many injuries that lead to haemorrhage. Helmets protect against head injuries that could cause brain bleeds. Proper workplace safety protocols, especially in high-risk occupations, help prevent crushing injuries and other trauma.^[2]

For individuals with bleeding disorders, prevention focuses on avoiding injuries and managing the underlying condition properly. Taking clotting factor replacement medications as prescribed helps prevent spontaneous bleeding episodes. Many people with hemophilia benefit from prophylactic treatment, where they receive regular infusions of clotting factors to prevent bleeding rather than waiting to treat bleeds after they occur. Avoiding contact sports and activities with high injury risk is often recommended. When injuries do occur, prompt treatment can prevent minor bleeds from becoming serious.^[16]

Managing chronic health conditions that increase haemorrhage risk represents an important preventive strategy. Keeping blood pressure well controlled through medication, diet, and lifestyle changes significantly reduces the risk of brain haemorrhage and haemorrhagic stroke. People with liver disease should avoid alcohol and receive appropriate treatment to preserve liver function and maintain adequate clotting factor production.^[1]

For people taking medications that increase bleeding risk, careful management and monitoring are essential. Regular blood tests to check medication levels and clotting function help ensure that anticoagulant doses remain in the safe and effective range. Patients should inform all their healthcare providers, including dentists, about blood-thinning medications before any procedures. Avoiding medications that further increase bleeding risk, such as not taking aspirin or ibuprofen unless specifically directed by a doctor, is important. Maintaining a list of all medications and supplements helps prevent dangerous interactions.^[5]

Nutrition plays a role in preventing certain types of haemorrhage. Adequate vitamin K intake supports normal clotting factor production. Good sources include leafy green vegetables, broccoli, and other vegetables. However, people on blood thinners like warfarin need to maintain consistent vitamin K intake rather than sudden large changes, as this vitamin can affect medication effectiveness. Some individuals with bleeding disorders benefit from dietary adjustments recommended by nutritionists familiar with their condition.^[16]

During pregnancy, receiving proper prenatal care helps identify risk factors for postpartum haemorrhage before delivery occurs. Healthcare providers can plan ahead for high-risk deliveries by having additional staff and resources available. After previous episodes of postpartum haemorrhage, medications may be given during subsequent deliveries to help the uterus contract properly and prevent excessive bleeding.^[13]

Education about recognizing early warning signs of haemorrhage enables people to seek help quickly when problems develop. The “Stop the Bleed” campaign, launched in 2013, teaches laypersons basic techniques for controlling severe bleeding in emergency situations. This type of public education can save lives by reducing the time before proper bleeding control measures are applied.^[2]

Pathophysiology: What Happens in the Body During Haemorrhage

Understanding the physical and biochemical changes that occur during haemorrhage helps explain why blood loss can be so dangerous and why the body sometimes struggles to stop bleeding on its own.

When a blood vessel is damaged, the body normally initiates a complex process called hemostasis to stop the bleeding. This process involves three overlapping stages: blood vessel constriction, platelet plug formation, and blood clotting. First, the damaged blood vessel constricts or narrows to reduce blood flow through the injured area. Next, platelets, which are small cell fragments circulating in blood, stick to the damaged vessel wall and to each other, forming a temporary plug. Finally, a series of chemical reactions involving clotting factors produces threads of a protein called fibrin, which weave through the platelet plug to form a stable clot.^[6]

When haemorrhage occurs, this normal hemostatic process may be overwhelmed or may not function properly. In traumatic injuries, the damage to blood vessels may be so extensive that the body cannot form clots quickly enough to stop the bleeding. Large or major blood vessels, particularly arteries, carry blood under high pressure, making it especially difficult for clots to form and seal the injury.^[1]

As blood loss continues, the volume of blood circulating in the body decreases. The cardiovascular system attempts to compensate for this loss through several mechanisms. The heart beats faster to circulate the remaining blood more quickly. Blood vessels in the skin, digestive system, and other less vital organs constrict to redirect blood flow to the brain, heart, and kidneys. These compensatory mechanisms explain why people experiencing haemorrhage develop rapid heart rate, pale or clammy skin, and cold extremities.^[5]

However, these compensatory mechanisms have limits. When blood loss exceeds about 30 percent of total volume, compensation begins to fail. Blood pressure drops dangerously low, reducing the driving force that pushes blood through small vessels to tissues. Organs and tissues begin to suffer from inadequate oxygen delivery, a condition called tissue hypoxia. Without oxygen, cells cannot produce energy efficiently and begin to malfunction or die.^[1]

The brain is particularly sensitive to oxygen deprivation. Even brief periods of inadequate blood flow can cause confusion, loss of consciousness, and potentially permanent brain damage. The kidneys also suffer quickly from poor blood flow, potentially leading to acute kidney failure. If bleeding continues unchecked, multiple organs may fail, resulting in death.^[2]

Severe haemorrhage can trigger a dangerous condition called coagulopathy, where the blood loses its ability to clot properly. Several factors contribute to this problem. The blood becomes diluted as the body shifts fluid from tissues into blood vessels to maintain volume. This dilution reduces the concentration of platelets and clotting factors available to stop bleeding. Blood loss itself depletes clotting factors and platelets faster than the body can replace them. Hypothermia, or low body temperature, which often occurs with severe blood loss, impairs the chemical reactions necessary for clotting. The buildup of acid in the blood, called acidosis, also interferes with clotting mechanisms. This creates a vicious cycle where bleeding causes coagulopathy, which in turn makes the bleeding worse and harder to control.^[2]

In postpartum haemorrhage, the uterus normally contracts strongly after delivering the placenta, compressing the blood vessels where the placenta was attached. When the uterus fails to contract adequately, a condition called uterine atony, these vessels bleed freely. This is the most common cause of postpartum haemorrhage and explains why medications or other measures to promote uterine contraction are often the first treatment approach.^[13]

Brain haemorrhages create unique problems because the skull is a rigid container with limited space. As blood accumulates inside the skull, pressure builds up, compressing brain tissue. This intracranial pressure can damage the brain directly through compression and can also reduce blood flow to brain tissue, causing additional injury from oxygen deprivation. Different types of brain haemorrhages affect different areas and have varying effects on brain function.^[1]

When blood collects in body cavities, it can interfere with organ function mechanically. Blood in the chest cavity around the lungs can compress the lungs and make breathing difficult. Blood in the abdomen can cause pain and swelling. In compartments surrounded by tough, inelastic tissue like muscles, bleeding can create dangerous pressure that compresses nerves and blood vessels, potentially causing permanent damage if not relieved quickly.^[1]