Highly stable, simple to collect, and easy to ship and store, fingernails provide a test sample at the cutting edge of drug and alcohol testing. Fingernails are made up of keratin, the same material that hair is made of. As the nail grows, substances can pass from the blood vessels below the nail into the keratin fibers, where they become trapped. Fingernails are four times thicker than the typical strand of hair and often capture more substance than hair can. Biomarkers become locked in keratin fibers along the entire nail length and can be detected up to 3-6 months after drug or alcohol use. Environmental exposure to illicit substances can be detected immediately in nail samples. When drugs or alcohol are ingested, biomarkers can be found in nails as early as 1-2 weeks after. The time period during which drug or alcohol ingestion can be detected depends on the substance used, the amount used, and personal metabolism.
 
Fingernail samples are clipped and collected by the donor in front of a trained collection staff member. A clipping of 2-3 mm long (about the width of a quarter) from all ten fingernails will give about 100 mg of sample, the ideal amount for screening and confirmation. Larger profiles may require more.