The present invention is directed to a coupler for providing fluid connection between a needle holder and an intravenous needle assembly. The coupler includes a coupler housing and a coupler needle cannula. The coupler housing includes a forward end and a rearward end with the forward end having a piercable septum. The coupler housing also includes at least one lug on its external surface. The coupler is capable of forming a blood collection assembly to provide for fluid connection between a conventional needle holder and an intravenous needle assembly which includes guide slots traditionally provided for engagement with lugs on specific specimen tube arrangements.