Which method of drug testing is the best?

Detection periods

The following chart from LabCorp gives approximate detection periods for each substance by test type.^[1] The ranges depend on amount and frequency of use, metabolic rate, body mass, age, overall health, and urine pH. For ease of use, the detection times of metabolites have been incorporated into each parent drug. For example, heroin and cocaine can only be detected for a few hours after use, but their metabolites can be detected for several days in urine. In this type of situation, we will report the (longer) detection times of the metabolites.

• NOTE 1: Oral fluid or saliva testing results for the most part mimic that of blood. The only exception is THC. Oral fluid will likely detect THC from ingestion up to a maximum period of 18-24 hours
• NOTE 2: Urine can not detect current drug use. It takes approximately 6–8 hours or more post-consumption for drug to be metabolized and excreted in urine. Similarly, hair requires two weeks, and sweat, seven days.

Approximate values for detection periods

Substance	Urine	Hair	Blood
Alcohol	3–5 days via ethyl gluconoride (EtG) metabolite or 10–12 hours via traditional method	lifetime of hair	12 hours
Amphetamines (except meth)	1 to 2 days	up to 90 days	12 hours
Methamphetamine	2 to 4 days	up to 90 days	24 hours
Barbiturates (except phenobarbital)	2 to 3 days	up to 90 days	1 to 2 days
Phenobarbital	7 to 14 days	up to 90 days	4 to 7 days
Benzodiazepines	Therapeutic use: 3 days. Chronic use (over one year): 4 to 6 weeks	up to 90 days	6 to 48 hours
Cannabis	Light use: 2-7 days Prolonged use: 1-3 months	up to 90 days	12 days
Cocaine	3 to 300 days with exceptions for certain kidney disorders	up to 90 days	24 hours
Codeine	1 day	up to 30 days	12 hours
Cotinine (a break-down product of nicotine)	2 to 4 days	up to 90 days	2 to 4 days
Morphine	2 days	up to 90 days	6 hours
Heroin	2 days (single use) 2-5 (chronic)	up to 90 days	6 hours
LSD	2 to 24 hours	up to 3 days	0 to 3 hours
Methadone	3 days	up to 30 days	24 hours
PCP	14 days; up to 30 days in chronic users	up to 90 days	24 hours

This helpful information was provided by wikipedia.

Obviously the drugs remain longer in the hair follicle than they do any where else. American Toxicology recommends that both hair and urine drug testing be used for optimal results.