My friend is having a blood test. It checks for cbc, TSH and ft4. Will marihuana and alcohol show up in these test results?

NO. The test you mention would not show drug or alcohol levels.
Unlikely, unless . . If the doctor also orders a screen for specific drugs and alcohol level, these results would show up. If testing only for cbc, tsh, and free t4, they would not. If you're concerned about positive drug & alcohol testing, best to stay away from using those substances -- especially at age 15.