Question for my seasoned IV users

Okay so my usual spots are my wrists and hands. (Bad yes I know) There’s a vein like at the bottom of your hand, like almost at the wrist below your thumb; when I shoot there I can feel it burning up in several spots like up to my elbow, for about three seconds. I’m 100% not missing or losing the vein. Does anyone know why this is happening? (Other than yes I know I’m putting literal poison in my arm)