I got the PatchMD vitamin patches, and I'm scheduled for blood work in 2 weeks...

I definitely will  

By all means, try them. But the next two weeks won't tell you anything. You could take new vitamins, or none at all, and your labs won't show the difference. 

If it were me, I would continue taking your old vitamins for until your bloodwork is drawn, then switch to the patch. After 6 months or a year, compare your labs from the patch and regular vitamins and see if there's a difference.

That's a really good idea, I didn't think of that.  I was wondering if 2 weeks of use would be enough to even register on my labwork.

I took your advice, got my labs drawn today, and started my first patch after I got my lab work done.  I'll compare the results with the next round.

Thanks for the idea