@jamzzy I mean, that was obviously the question. I’m not too familiar with blood tests, but I think it depends on the context of the test. If it’s strictly a health-related blood test, I believe they check the (sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), magnesium, creatinine, glucose, and sometimes calcium) levels. Whether or not any abnormalities in these indicate the use of specific drugs, I do not know.
If they’re doing a drug test via blood analysis, they’re probably going to find anything you’ve done within the last few weeks, if not longer for synthetic drugs like LSD. I’m no expert in this area, so maybe someone else can help me out with whether or not certain drugs do not show evidence in the blood stream.