My sis went to the endocrinologist to get some blood work done. When they do the blood work do they test for drugs? Like weed or crack? Can that show up in the blood work?

Of course it can show up, if the blood test was job related versus illness related and if they specifically ask for the test to be done. Also if the GP thinks there may be a reason(drug related) for the disease, I think they would do it as well.

Don't you have an "amendment #" covering privacy etc. They may not be entitled to do the drug test without your /sister's consent.