Internal bleeding happens when a blood vessel (artery or vein) is damaged inside the body, so blood leaks into tissues, organs, or body cavities instead of out through the skin.

Main cause groups

  • Trauma/injury is the most common cause, especially from car crashes, falls, assaults, sports injuries, stab or gunshot wounds, and crush injuries. These can tear organs (like liver or spleen), bones, or major vessels and cause life‑threatening bleeding.
  • Non‑traumatic medical problems can also cause internal bleeding, including ulcers in the stomach or intestines, inflamed bowel conditions, tumors or cancers, and ruptured aneurysms (bulges in arteries such as the aorta or brain).
  • Problems with clotting or blood vessels (genetic disorders like hemophilia, severe liver disease, vitamin K deficiency, or fragile/abnormal vessels) can make even small leaks inside the body bleed a lot.

Common specific causes

  • High‑impact accidents or blunt trauma that injure organs (head, chest, abdomen) and major bones like the pelvis or femur.
  • Penetrating trauma (stab or bullet wounds) that cut through vessels or organs and bleed into the chest or abdomen.
  • Gastrointestinal causes such as peptic ulcers, gastritis, Crohn’s disease, colitis, polyps, esophageal varices, or GI cancers, which can bleed into the digestive tract.
  • Ruptured aneurysm (for example in the aorta or brain) or ruptured ectopic pregnancy, both of which can suddenly cause massive internal bleeding.

Medicines and risk factors

  • Blood thinners (anticoagulants like warfarin, DOACs; antiplatelets like aspirin) and frequent use of NSAIDs (such as ibuprofen) increase the risk or severity of internal bleeding.
  • Long‑term high blood pressure, heavy alcohol use, some antibiotics, steroids, and certain chronic conditions (liver, kidney, or spleen disease, cancers, clotting disorders) also make bleeding more likely or harder to stop.

When to treat it as an emergency

  • Sudden severe pain, dizziness, fainting, confusion, cold or pale skin, rapid heartbeat, vomiting blood, coughing blood, black or bloody stools, or a very swollen/tender abdomen can all signal dangerous internal bleeding and need immediate emergency care.

Information gathered from public forums or data available on the internet and portrayed here.