Some test I am sure can be fooled during those time frames but not the type they are administering, I am not really sure exactly how they look for the substances in the blood stream since I am not a doctor or scientist but I do know that DNA testing for substances can not be hidden, If you have any substance in your body that has been used for a long period of time it is almost impossible to hide once they know exactly what it is they are looking for.

A perfect example would be cocaine or Marijuana. In urine testing I believe one stays visible for a week or two, the other 30-90 days, in the blood it raises up to something like a month for one and a year for the other. In hair testing it can remain for years.

In small biopsies of the skin and it takes just a scratch something like steroids can show up for the duration of your life,

Things are so advanced today it is just about impossible to hide anything even after long periods of time