Drug Testing

When injecting drugs into your body, whether they were inhaled, drank, eaten or injected by needles, drugs show up in your body's system.
Many drugs can be easily detected by a simple drug test.
Drugs can be detected by either a blood sample, saliva sample, urine sample, or breath test.
Usually, alcohol tests are tested by breathalyzers, marijuana[since it's inhaled] is usually in the blood and urine system. So this can easily be tested with a urine sample.
Cocain, ecstasy and angel dust, become part of the blood system and can be easily tested with a blood sample.

Although, one doesn't necessarily need to take a drug test to show that they are not sober.
When drunk on alcohol, one tends to slur their words and wobble as they walk. These are sure signs that someone is drunk.
When someone is under the influence of marijuana their eyes mite turn red and diluted.
When on is on cocain, angel dust, or ecstacy their nose mite turn red and possibly start to bleed and their face will either be very excited or very tired.