A protecting mechanism for a blood sampling device contains: a trigger unit and a switching assembly. The trigger unit includes a lancet holder, a triggering shaft, and a resilient element. The lancet holder has a launching portion, a first outer protrusion, a through orifice, and a first inner shoulder, wherein a bottom end of the triggering shaft moves in the through hole, and the triggering shaft has a first outer shoulder for engaging with the first inner shoulder of lancet holder, the resilient element is fitted with the triggering shaft and abuts against the lancet holder by ways of its bottom end. The switching assembly includes a fixing jacket having an abutting portion, a rotating tube having a first inner protrusion and two opposite second inner protrusions, and a driving sheath having two stopping sets, wherein each stopping set has two second outer protrusions.一種用於採血筆之安全保護機構,包含有一擊發單元與一切換開關,擊發單元具有一針頭保持座與一穿設於針頭保持座內之擊發桿,切換開關具有一設於針頭保持座之固定套件、一設於固定套件之旋轉套件,以及一設於擊發桿之連動套件,當旋轉套件位於一待擊發位置時,針頭保持座能帶動擊發桿往上移動,直到與固定套件完成卡接時即完成上膛擊發之準備,此時的連動套件會受到旋轉套件之限制而無法推動擊發桿進行退針,當旋轉套件位於一退針位置時,針頭保持座固定於固定套件內而無法上膛,此時的擊發桿能藉由連動套件之推動而進行退針操作。12‧‧‧筆身124‧‧‧開關14‧‧‧筆蓋16‧‧‧針頭18‧‧‧安全保護機構20‧‧‧擊發單元21‧‧‧針頭保持座211‧‧‧擊發孔213‧‧‧第一外擋止部214‧‧‧缺口215‧‧‧觸發部22‧‧‧擊發桿23‧‧‧擊發彈性件25‧‧‧殼體252‧‧‧套孔254‧‧‧內卡合部26‧‧‧推頂環261‧‧‧環體262‧‧‧第二內肩部263‧‧‧延伸臂264‧‧‧外卡合部27‧‧‧復位彈性件28‧‧‧端蓋30‧‧‧切換開關40‧‧‧固定套件42‧‧‧保持孔44‧‧‧承靠部50‧‧‧旋轉套件51‧‧‧第一內擋止部52‧‧‧第二內擋止部53‧‧‧彈性抵壓部60‧‧‧連動套件64‧‧‧第二外擋止部
