There are three different types of bruises depending on their size. A Bruise between 1 to 3 cm in diameter is known as an Ecchymosis, a purpura if it is between 3 mm and 1 cm or a petechia if it is less then 3 mm, however these terms can also refer to trauma causing internal bleeding.
Brusies are categorized according to the following table:
| Harm score | Severity level | Notes |
| 0 | Light bruise | No damage |
| 1 | Less than Moderate bruise | Little damage |
| 2 | Moderate bruise | Some damage |
| 3 | Serious bruise | Dangerous |
| 4 | Extremely serious bruise | Dangerous |
| 5 | Critical bruise | Risk of death |
Bruising that has a harm score between 2 and 3 can be dangerous and without proper attention can cause serious complications. Excessive bleeding can cause a hard lump or hematoma in the body which can cut off circulation to other parts of the body. Requiring strong force to have started there may be other severe or potentially fatal damage to internal organs. Impacts to the head can cause swelling of the brain which can cause coma or death. Treatments for brain injuries usually involve emergency surgery to relieve pressure.
Other injuries may cause broken bones or tendons behind the bruise that may not be noticed at first and only initially appear as simple bruising. If the bruise causes difficulty moving or extending in places such as the knee may indicate a life threatening injury and should be examined by a medical professional.