What Are Fentanyl Test Strips?

This resource was initially published in early 2023. We updated this resource in February 2025.

Fentanyl test strips are small strips of specialized paper that inform us of the presence of fentanyl in samples of drugs and urine.

Similar to dipstick pregnancy tests or instant urine drug screens, fentanyl test strips display red lines to show positive or negative readings. Positive results show one line; negative results show two lines.

How do fentanyl test strips (FTS) prevent overdose?

FTS provide people who use drugs with crucial information that can help prevent drug overdose. Drug users who get positive test results are likely to adopt safer drug use behavior.

One International Journal of Drug Policy study shows people who inject drugs who received a positive test result were five times more likely to change their drug use behavior than those with a negative result. Such behavior changes include:

• Trying new batches of drugs with small test doses
• Only using drugs when around a friend with naloxone (e.g., NARCAN^®)
• Disposing of the drugs that tested positive
• Informing suppliers of the positive results, and finding new sources to get uncontaminated drugs from

How to use fentanyl test strips

Here’s how to test for fentanyl in a sample of drugs:

1. Crush drugs into a fine powder.
   • If injecting drugs, prepare your shot as normal and proceed to step two.
2. Mix drugs with water.
   • WARNING: Some substances can cause false positives. To minimize the risk of false positive results, different drugs require different amounts of water (dilution).
     • If using WiseBatch strips, visit their website’s Resource page for dilution instructions.
     • If using DanceSafe strips, visit their website’s “New Fentanyl Test Strips” page for dilution instructions.
     • If using Dosetest strips, visit their website’s “Fentanyl Test Strip App” page for dilution instructions.
     • If using BTNX “Rapid Response” strips, DanceSafe’s “Older Fentanyl Strips” page has dilution instructions.
3. Dip test strip into water.
4. Lay strip aside and await results.

Are fentanyl test strips legal in Tennessee?

Yes, fentanyl test strips are legal in Tennessee — except when used in the manufacture, delivery, or sale of a controlled substance, per Tenn. Code Ann. § 39-17-417.

On March 31, 2022, Tennessee Governor Bill Lee signed HB 2177/SB 2427 into law, removing “narcotic testing equipment used to determine whether a controlled substance contains a synthetic opioid” (like fentanyl test strips) from Tenn. Code Ann. § 39-17-402(12)(B) — the statute that defines “drug paraphernalia.”

What you should know about the FTS market

Brands aren’t manufacturers

Countless brands sell their own fentanyl test strips. These brands don’t actually make their own strips, though. Rather, they pay for private-label manufacturing services.

Private-label manufacturing is where companies pay factories to make products to their specifications. You know how off-brand products

Today, many brands of fentanyl test strips are available to consumers. Although they all promise high degrees of reliability, the truth isn’t as glamorous.

Many show false positives for substances commonly found in illicit drugs and can have high lot-to-lot variability (i.e., two strips from the same brand may not work the same).

When harm reduction organizations began using FTS to test drug samples in the mid-2010s, test strips manufactured by Assure Tech became the industry standard. Initially, Assure Tech strips were only available through BTNX,, a canadian forensic who sells the green “Rapid Response” tests. In recent years, other brands have begun selling Assure Tech strips, including WiseBatch and Dosetest. Assure Tech fentanyl test strips show false positive results for methamphetamine, MDMA, methadone, and common additives found in illicit cocaine.

In 2022, WHPM began manufacturing FTS, different from those made by AssureTech. A WHPM-funded study performance review suggests WHPM’s fentanyl test strips show false positives for none of the same substances as AssureTech. However, both still show positive results for diphenhydramine (Benadryl), a cut sometimes found in illicit powdered opioids (e.g., fentanyl, heroin).

Sadly, the FTS market is shrouded in mystery and misunderstanding. Brands rarely — if ever — manufacture their own strips, usually never disclose who manufactures them, and often fail to include instructions for testing illicit drugs.

That said, we feel compelled to support fentanyl test strip brands that:

1. Are clear about where their test strips come from
2. Have reseach supporting their efficacy
3. Include on-package instructions
4. Make in-depth instructions available on their websites

What brands of FTS are available?

We recommend WHPM’s fentanyl test strips, which can be bought from Grassroots Harm Reduction and DanceSafe. However, AssureTech’s fentanyl test strips are better than nothing. If you can’t get WHPM products, we’d then recommend a few well-known brands of AssureTech FTS: WiseBatch, Dosetest, and BTNX “Rapid Response” fentanyl test strips — the image below summarizes our findings and opinions on each of these brands:

Note: This graphic was made in early 2023. This graphic is outdated in the following ways:
1. DanceSafe is no longer the only brand selling WHPM fentanyl test strips.
2. Dosetest now includes on-package instructions.
3. BTNX offers instructions for use on its website.

Where can I find fentanyl test strips for sale?

While you probably won’t find fentanyl test strips for sale in Walgreens, CVS, or any other brick-and-mortar stores anytime soon, a quick google search will reveal dozens of places to buy fentanyl test strips. Again, we recommend buying WHPM fentanyl test strips, but also recognize Assure Tech FTS are better than nothing.

If possible, buy your strips directly from the brand you’re looking for. Three of our recommended brands sell their strips directly to consumers: DanceSafe, WiseBatch, and Dosetest.

This page no longer tracks pricing for each brand of FTS we’ve discussed; it’s time-consuming and, since brands are free to change prices at will, it’s easy for us to have outdated information. Rather, here’s the lowest price we’ve found each brand of FTS for as of February 2025:

• Assure Tech: $0.385/strip (Dosetest)
• WHPM: $0.89/strip (Grassroots Harm Reduction)

Some brands offer lower pricing for harm reduction projects. You may find lower prices by contacting these brands and asking for discounts.

Where can I find free FTS in Tennessee?

To our knowledge, there are three ways to get free fentanyl test strips in Tennessee:

• Syringe Services Programs
  • This is what the Tennessee Department of Health calls state-approved harm reduction projects. TDH provides SSPs with fentanyl test strips. SSPs must give out supplies for free to maintain state approval.
• Other harm reduction projects
  • This refers to harm reduction projects that aren’t state-approved. Keep in mind harm reduction projects don’t need state approval to be legal, legitimate, or reputable.
• Regional Overdose Prevention Specialists
  • ROPS are state employees who offer overdose response trainings and give out naloxone and FTS.

Beginning in November 2022, TDH began providing test strips to Syringe Services Programs (SSPs) and Regional Overdose Prevention Specialists (ROPS).

To our knowledge, TDH stocked Assure Tech fentanyl test strips as of late 2023. If you ask an SSP or ROPS for fentanyl test strips, ask if they carry WHPM products (DanceSafe, Grassroots Harm Reduction).

Generally, states enter contracts to purchase certain brands of products like FTS or naloxone. These contracts often last for years. As WHPM’s test strips are newer to the market, some states have been slow to adopt this superior product.

For these reasons, tread carefully when sourcing FTS for free in Tennessee. You’re better off buying them from brands known to stock WHPM fentanyl test strips, such as DanceSafe or Grassroots Harm Reduction.

READ MORE: What Do Tennessee’s Regional Overdose Prevention Specialists Do?

Best practices for preventing drug overdose deaths

• Embrace drug checking. Drug checking — commonly confused with drug testing — helps people figure out what substances their drugs contain, reducing the risk of overdose and other adverse reactions. Examples of drug checking tools include fentanyl test strips, drug reagents, and having your drugs lab-tested.
  
• Keep naloxone around. Even if you get a negative result, fentanyl test strips are not a replacement for naloxone. Keep naloxone in your car, at home, and everywhere else you go in a day’s time.
  
• Don’t mix drugs. Most drug-related deaths occur from combined drug intoxication (i.e., mixing two or more drugs). If you use drugs, try your best to only take one substance at a time. If you decide to combine drugs, use this drug combination reference app from TripSit to help you avoid particularly dangerous drug interactions.