When you swing and jab the EpiPen® into your thigh, the needle and the dose of adrenaline will be released. After removing the EpiPen®, the orange end will extend to cover the needle and the viewing window will go dark. There will still be some adrenaline left in the pen, and this is perfectly normal. You will quickly start to feel that the adrenaline is working. Remember, each EpiPen® can only be used once.