Hello tpwyu,
The Medicare taxes will be adjusted on form 8959. If you paid too much medicare tax throughout the year the excess will be applied to your taxes withheld (Line 64 on form 1040 for 2017).
If you had not paid enough Medicare taxes on your wages or self-employment income during the year - the shortage would also be adjusted on form 8959 as an additional tax (on line 62 on form 1040 for 2017).
I hope this Answers your question,
Jack
