As of January 1, 2013, The IRS has added an additional medicare tax. For all joint filers, the additional medicare tax is $250,000.00 or more. This is a new tax that you pay (when filing your tax return) in addition to the medicare taxes you pay when you work as an employee.
Additionally, the social security and medicare taxable wage limits for 2014 have been increased to $117,000.000. What this means is that all wages up to 117,000.00 (per year) are taxed with both social security and medicare taxes. Once this limit is reached, the social security taxes are no longer taken out of your wages.