Nail Testing for Drugs and Alcohol

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Nails, a keratinized protein like hair, are emerging as a popular specimen type, especially for court ordered tests. Fingernail drug tests for toxicological analysis and pharmacokinetic studies have been around for decades.

Nail testing for drugs

When drugs are ingested, biomarkers can be found in nails as early as 1-2 weeks after ingestion. The time during which drugs are ingested can be detected depending on the substance used, the amount used, and personal metabolism.

A nail alcohol test for EtG, a biomarker test that can detect the presence of ethyl glucuronide in a variety of specimen types, promises a much wider window of detection.

Nail clipping tests for drugs are becoming more popular for testing in the criminal justice system and in treatment facilities. This is largely because nail bed testing is much more difficult to fake than urine tests. And also because of how far a nail bed drug test can go back.

Drugs are distributed via the blood supply to the nail cells and the nail bed. Nails grow not only in length but in thickness as well. As the nail grows in thickness, it creates layers of drug history.

There are a limited number of references in the literature that fully describe the window of detection, but the available literature indicates that some drugs wash out as quickly as 3 months, while some can be retained for many more months.

The detection limit depends on the age of the nail material, which for the average person is 5-6 months minus the washout rate. However, some individuals may have slightly faster nail growth while others may have somewhat slower. Also, a major consideration in the detection window is the original drug exposure level.

What we know is that fingernails have a long window of detection: longer in some instances than hair. There are many factors that determine the window of detection.

Nail testing for alcohol

While urine tests track alcohol usage for a short window of time, fingernails and toenails provide a longer window. These tests are often used for individuals on probation to trace their history back several months. If you need a multi-month test for alcohol, nails often make for the best specimen.

Nail Testing FAQ

While urine tests track alcohol usage for a short window of time, fingernails and toenails provide a longer window. These tests are often used for individuals on probation to trace their history back several months. If you need a multi-month test for alcohol, nails often make for the best specimen.
How far back do your nails test for drugs?

Nails are keratinized protein, and nails are porous. Compounds become trapped and bound within the structure of the nail. The entire process takes up to 6 months, depending on the health of the individual.

Compounds are incorporated into the fingernail via four main routes:

  • Environmental exposure…if someone is handling a drug or around someone smoking a drug, the substance gets on the nail and into the pores, and binds to the keratinized protein.
  • Perspiration and skin oil surrounding the nail…causes deposits of the drug and drug metabolite into the nail.
  • Blood flow in the germinal matrix…deposits drug and drug metabolite into the nail when it is formed.
  • Drug and drug metabolite deposits…form on the underside of the nail plate, due to the blood flow to the nail bed.

These four very different routes of incorporation are superimposed in layers, rendering a very complex drug history.

For fingernail drug tests, the detection window is up to 6 months while toenail drug tests have a potential window of detection up to 12 months.

Just like with hair and urine tests, a negative result is not proof of abstinence. It’s only the lack of evidence. A positive fingernail result for most drugs may be explained by drug use at any point during the 6 months prior to the collection. Since the clipping contains the entire drug history in the growth of the nail, a nail scraping is not necessary.

Nail drug tests vs. hair drug tests
Fingernails are often preferred over hair tests because fingernails typically can trace drug use for a longer period of time than hair. Additionally, if the subject removes their hair from their body, hair testing becomes difficult.