When exploring drug testing to ensure a drug-free workforce, you have several modalities to choose from. Urinalysis, the most popular method, offers a quick response time from laboratories but only gives technicians a short window of detection—generally 24 to 72 hours. Saliva testing is minimally invasive, easy to observe, and almost impossible for subjects to circumvent, but it offers an even shorter window. Blood testing, with a brief window of detection and the invasive nature of drawing blood, is far more likely to find use in emergent legal issues than in standard testing as a condition of onboarding or continued employment.

For discreet procurement and detection windows that last months, not hours, two means of drug testing tower above the rest: hair testing and fingernail testing. Similar in some respects, they’re still quite distinct methods of screening for illegal and abused drugs. Today, we’ll examine the difference between hair and fingernail testing to help you decide which approach will best suit your needs.

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How Are They Similar?

Before hair and nail testing diverge, they share an important commonality. Our hair and our nails are made of keratin, a fibrous protein that occurs throughout the fins, fur, feathers, hair, and hooves of the animal kingdom. Drug testing keratin-based samples relies on detecting drug metabolites that become embedded in the fibers, where they reside for 3 to 6 months.

Differences in Detection Windows

Deposits of metabolites settle amid the fibers of hair and nails, but the duration for which they stay there differs between hair and nail specimens. The detection window for most metabolites in hair is generally around 90 days. This makes hair tests particularly useful in identifying long-term patterns of drug abuse that short-window tests of urine and saliva would not indicate. Furthermore, if the specimen donor has long enough hair (longer than 1.5 inches), segmented hair testing can be done to go beyond the estimated 90 days of detection. This is performed in increments of 90 days, and as long as you have the appropriate length, we can order a hair test going back 6 months, 9 months, and even one year and beyond. You will need 1.5 inches of head hair length for every 3 month increment. For example, you will need 6 inches to get a 1-year hair drug test. Body hair collections are also an option, but not for segmented time frames. However, with hair drug testing, ultraviolet light, water, and detergents cause these metabolites to break down—other keratin samples could retain them much longer.

Nail tests effectively double the window thanks to the relative hardiness of nail-based keratin, allowing up to 6 months for lab technicians to look back on a variety of drug uses. Some toenail samples can even offer up to 12 months of insight into potential substance abuse.

Differences in Potential for Contamination

Hair is good at picking up byproducts of drug use—in some cases, perhaps too good. The difference between hair and fingernail testing looms large when it comes to the possibility—however remote—that a hair sample has picked up false positives from environmental exposure. A porous hair shaft can pick up airborne drug metabolites, which then become embedded in the shaft and deliver a false positive. Fingernails and toenails are much less susceptible to this.

Still, the chances of this happening are rare. A hair drug and alcohol test is a highly reliable means of drug testing. Just know that you have the option for a nail test as a very solid backup.