Self-contained blood withdrawal apparatus and method

A piercing mechanism for piercing the skin to draw blood from a patient comprising:

• a base portion including a wall defining a cavity and an opening into said cavity;
• a resilient, fluid impermeable diaphragm positioned in said cavity opening in a manner preventing said drawn blood from flowing through said opening into said cavity;
• a piercing element capable of piercing movably disposed in said cavity;
• and
• an operating assembly cooperating with said piercing element to move said piercing element, relative said base portion, from a retracted position out of contact with said diaphragm, to a piercing position, extending through a hole in said diaphragm caused by said piercing element to pierce the skin proximate said cavity opening, and wherein said piercing element is capable of moving back to said retracted position, said diaphragm being sufficiently resilient to self-seal said hole and prevent blood from flowing therethrough upon retraction of said piercing element therethrough.