Can Medicare and OASDI tax be deducted out of my check? If part of the OASDI tax goes to medicare why is my employer taking out both taxes from my paycheck. I live in Arizona.

No, you are not being overtaxed. This site explains it: OASDI Tax - What is OASDI Tax, What is OASDI Tax Rate, OASDI Rate, OASDI limit, What is OASDI (http://www.oasdi.net/)