Under the Patient Protection and Affordable Care Act the Medicare tax rate will increase to 2.35% from 1.45% (employee withholding only) on wages paid over $200,000.  This will become effective with the 2013 taxable year.  The IRS has posted questions and answers on their website to help employers.

http://www.irs.gov/businesses/small/article/0,,id=258201,00.html