It depends on the source of the hemorrhage. Exsanguination is the term for bleeding to death. If the bleeding is from an arterial source, death may only take 20 seconds to a couple of minutes. Keep in mind though that the particular artery involved will determine how quickly you bleed out. If the blood vessel is a large one like the abdominal aorta, and if this vessel was lacerated in half, then massive hemorrhage ensues and death comes in literally 20-25 seconds. If the artery is smaller in size, and no first aid was received by the victim, then death will come in 2-3 minutes.

Acute bleeding from a venous source takes a longer period of time to cause damage and death. Here again, it depends on the location of and size of the vein. Damage to larger veins like the superior vena cava will result in death in 4-6 minutes. Bleeding from smaller veins will take longer, assuming of course, that no first aid was received.

The answer to your question depends on the type of injury and the amount of blood loss per minute.  Obviously a more severe injury involving one of the body's major veins or arteries would result in death much quicker than a knife slice to the forehead.  Most people can lose 10-15% of their blood volume before there is a serious medical concern.

Bleeding is technically known as hemorrhaging. Hemorrhaging can be broken down into five classes.

1. Class I Hemorrage-involves losing up to 15% of the body's blood volume. Patient remains okay.
2. Class II Hemorrhage-involves losing up 30% of the body's blood volume. Patient may have a rapid heartbeat, look pale, and be cool to the touch.
3. Class III Hemorrhage-involves losing between 30-40% of the body's blood volume. The patient's blood pressure drops and he/sh goes into shock. A blood transfusion is most likely needed.
4. Class IV Hemorrhage-involves losing more than 40% of the body's blood volume. At this stage, the individual dies if not resuscitated.

Another word for excessive bleeding is called hemorrhaging. Generally, a person can lose 10-15% of their entire blood volume and still survive without any major medical difficulties.

There are different classifications of blood loss:

1. Class 1 Hemorrhage-up to 15% blood loss
2. Class 2 Hemorrhage-up to 15-30% blood loss
3. Class 3 Hemorrhage-up to 30-40% blood loss
4. Class 4 Hemorrhage->40% blood loss

If a person has a major artery severed, death can occur in as little as a few minutes. Others types of bleeding may take longer. It really depends on the injury or complication that we are talking about.

Certain medications, such as blood thinners, can lead to excessive bleeding as well. These people do not have the clotting abilities that normal people do .