Does an LLC have to be reported on Schedule C if it is used for investments?

[SusanY1]

Not necessarily.  Schedule C is only used to report income from self-employment.  An LLC can have any number of tax structures, and may or may not lend itself to a Schedule C. 

If you are the sole owner of the LLC, and your investments simply pass through to you as an individual, you can report them on your tax return without regard to the LLC as the IRS will see it as a disregarded entity anyway.