For the year 2013 the IRS allowance is 24 cents per mile.
(Driven miles for medical or moving purposes -
up 1 cent per mile from last year)
Here is another link for 2012 mileage deductions
Each year it has been slightly less than half of the allowance deduction for business miles.
Even though it is a small amount of money it adds up and you should take advantage of every deduction that you can.
Miles driven have to be recorded at the time that they are driven.
(Not while driving the car though)
For any year, you should print the free mileage log on this site.
The Internal Revenue Service will be concerned about the accuracy of these records.
The IRS won't let you just guess and fill it all in at the end of the year they want it to be exact.
Consider a trip from a small town to a bigger city for specialized treatment once a week.
If the medical facility is 50 miles from home you have to drive back as well, so it is a 100 mile trip.
The medical mileage rate allowance would give you a worthwhile deduction per trip.
If you make the trip once a week for 10 weeks, you could take a ten times larger medical mileage deduction.
Again use the mileage log.