To make your life simpler, the Internal Revenue Service sets a standard mileage rate that you can use to figure your mileage deductions if you drive for medical or charitable purposes. As of 2014, you can deduct 23.5 cents per mile for medical mileage and 14 cents per mile for charitable mileage.
The deductible costs of operating an automobile for charitable and medical purposes are both itemized deductions, which means you can only claim them if you forgo the standard deduction. If you take the standard deduction, you won't get any credit for your mileage. In addition, the IRS website says that for medical expenses, "you may deduct only the amount by which your total medical expenses exceed 10% of your adjusted gross income or 7.5% if you or your spouse is 65 or older." This includes mileage expenses.
Mark Kennan is a writer based in the Kansas City area, specializing in personal finance and business topics. He has been writing since 2009 and has been published by "Quicken," "TurboTax," and "The Motley Fool."