Bleeding or haemorrhage is the loss of blood due to damage to a blood vessel or organ. In internal bleeding there is leaking of blood inside the body. In external bleeding the loss of blood is through a break in the skin or through mouth, nose, ear, urethra, anus or vagina. Bleeding can occur due to injury, certain medications, bleeding disorders, menorrhagia, radiotherapy, etc. Bleeding that is allowed to continue can cause a huge decrease in blood volume (hypovolemia). The term exsanguination refers to bleeding to death. Haemostasis is stopping or controlling of bleeding.
Blood loss due to bleeding can range from minor to severe. Our body can bear a loss of 10–15% of the total blood volume without any serious complications. A loss of 15-30% of total blood volume can cause pale skin and speedy heartbeat. The lost blood volume needs to be restored. A loss of 30-40% of blood volume can decrease blood pressure, increase heart rate, decrease blood flow to organs, and cause behavioural changes. Fluid restoration and blood transfusion may be necessary. A loss of more than 40% of circulating blood volume can cause serious consequences, even death. It requires aggressive revival treatment.