The present invention provides a biological fluid collection device that includes a first end, a second end, and a sidewall extending therebetween defining a tube body. The biological fluid collection device further includes a sample collection portion having a cavity defined by a portion of the sidewall adjacent the first end and a puncturing element adjacent the second end. The cavity has a sample collection bottom surface and an external diameter. The puncturing element is adapted for movement between a pre-actuated position and a puncturing position. The portion of the sidewall surrounding the puncturing element has an external diameter that is substantially the same as the external diameter of the sample collection portion. The biological fluid collection device of the present disclosure can be used to both pierce a patient's skin surface to initiate blood flow and to collect a blood sample within the cavity of the tube.
