When to charge taxes on an independent contractor invoice?

Hi,

I am a new self-employed doctor. I am more specifically a traveling relief doctor and provide medical services seeing patients at various hospitals. I provide invoices to the clinics that hire me and charge an hourly rate as well as a mileage rate. I pay monthly excise tax to my state Dept. of Revenue and pay quarterly self-employment taxes to the IRS. When I work, I only examine, diagnose, prescribe meds, and do occasional minor surgery. I utilize all the equipment and supplies of the clinic I am working at specifically. I do not sell anything or carry any personal inventory of meds, etc. My question is since I need to pay excise tax and self-employment tax do I need to also charge some sort of tax on my invoices in addition to my hourly rate and mileage rate? Thank you!