Dizzy/Faint Feeling When I Get Up?

Hello, umm it seems like if im sitting down and then I get up I get this feeling that I am going to faint, and my vision becomes really blurry and I start seeing stars, and feel like I could fall over. This feeling goes away after like 30 seconds though. It happens almost every-time I get up from sitting. I think it has to do with my blood pressure, but I dont really know. Is this normal or not?