WARNING! – You may be using fentanyl testing strips incorrectly!
Last Updated: December 23, 2022
WARNING! You may be using fentanyl testing strips incorrectly
By Emanuel Sferios, DanceSafe founder
Photo: Our new micro scoops – available here – which are meant to improve the safety and efficacy of fentanyl strip testing.
A dangerous set of instructions for using fentanyl testing strips has been making rounds across the internet. For more than three years, I’ve been trying to correct this error whenever it appears, but like a game of Whack-A-Mole, it keeps popping up. It appears in Facebook posts by well-meaning harm reduction advocates, on the websites of reputable harm reduction organizations, and even in printed material distributed to people who use drugs.
I won’t link to these posts and pages, because I don’t want to further spread misinformation that could result in deaths. But I’m going to explain in full detail here what the issue is, how it came about (I’m partially responsible for it), and why we need to fix it immediately.
I ask you to help me fix it by sharing this article with every harm reduction advocate you know, and everyone you know who uses methamphetamine or MDMA. By the end of the article you will understand why.
First, a Precise Summary of the Problem
When testing methamphetamine or MDMA for fentanyl, you must dilute the sample you are testing down to 2mg/ml. This is about one teaspoon of water for every 10mg of powder or crystals. If it’s more concentrated, you may get a false positive result. If it’s more dilute, the strips may not be able to detect fentanyl or its analogues. A set of instructions has been going around telling methamphetamine users to add a few milligrams of meth into half a cup of water. This is way too dilute!
I’m going to explain in great detail why this is the case, as well as the history of how this misinformation came to appear.
Let’s start from the beginning…
Fentanyl Testing Strips as Harm Reduction Tools
By 2016, fentanyl-related deaths had begun to skyrocket. Fentanyl and its various analogues had saturated the heroin market in the US and Canada, and had also started appearing in cocaine, methamphetamine and counterfeit pharmaceutical pills. In December of that year I organized a study at the University of California San Francisco to assess the effectiveness of five fentanyl testing strips currently being sold on the market. Funded by DanceSafe, the goal of the study was 1) to determine if any of these strips were able to detect fentanyl and its various analogues in commonly used drugs; 2) if so, which brand of strips was the most effective; and 3) what the best practices were for using them. In other words, could any of these strips be used effectively for harm reduction purposes?
This was not a simple matter. All of these strips were originally designed for testing urine—not drugs—and so using them required first diluting the drugs in water. But how much water? It wasn’t enough to simply know that the strips could detect a specific fentanyl analogue at some unspecified dilution. We needed to know if they could detect all, or at least most, fentanyl analogues at a practical dilution. And we needed to make sure the strips didn’t produce false positives with other commonly used, non-fentanyl related drugs (and with common cuts added to those drugs) at similar dilutions. Specifically, we needed to know the maximum dilution point for each analogue the strips were capable of detecting (meaning the dilution point beyond which the strips could no longer detect that analogue), and the maximum dilution points for any substances that produced false positives (meaning the dilution point beyond which the strips would no longer produce a false positive).
Only by knowing these things could we determine whether the strips were useful in detecting fentanyl and its analogues when mixed with other drugs (rather than just inside urine).
False Positives with Methamphetamine and MDMA
I’m going to give you the full results of our lab study below, but generally speaking we discovered that the BTNX 20ng strips were the only brand capable of detecting a majority of the analogs at practical dilutions. (These are the strips we now sell, and the only fentanyl strips widely used for harm reduction purposes today.) They also did not produce false positives with most of the commonly used non-fentanyl related drugs and cuts at those same dilutions. However, we did discover that methamphetamine and MDMA can sometimes give false positives at concentrations of 5mg/ml or greater, and possibly even as low as 3mg/ml. (1)
What this means is that to avoid a potential false positive when testing meth or MDMA, one needs to dilute their dose using at least one teaspoon of water for every 10mg of powder or crystals. This is because a teaspoon is about 5ml (4.93), so adding 10mg of powder into one teaspoon of water results in a ratio of approximately 2mg/ml, and this falls below the concentration threshold that could trigger a false positive result.
So far so good, as long as you have a milligram scale and are willing to dilute your drugs in water. It is always recommended that you test everything you intend to consume, dissolving the whole sample in water, and for people who use MDMA this is less of a problem because MDMA is typically ingested orally. You can dissolve, for example, an entire 100mg dose of MDMA into 10 teaspoons of water (resulting in the proper 2mg/ml ratio), test it, and if it doesn’t contain fentanyl, simply drink it. It might taste bad, but you haven’t wasted anything.
People who use meth, on the other hand, typically use other routes of administration like snorting, smoking, or injecting the drug. Diluting any amount of meth in water, therefore, voids the first two options totally, and diluting it down to 2mg/ml also makes it impossible to inject. This is because a standard 1cc syringe holds only about 0.2 teaspoons of water, so if you dissolved 10mg of meth into a full teaspoon of water, you’d have to inject five full syringes to receive the full dose. If you wanted to inject 30mg of meth (not an uncommon dose for many IV meth users), you would need to inject a whopping fifteen times.
Testing the Residue in Your Spoon or Cooker
Although DanceSafe was the first organization to conduct an independent lab study assessing the sensitivity and cross-reactivity of fentanyl testing strips for use in harm reduction (in December of 2016), we were not the first harm reduction organization to begin using the strips, nor the first to develop protocols for how to use them. Organizations around the US and Canada who worked directly with people who inject heroin had been experimenting with fentanyl testing strips for a number of months already, and the method they determined was the best for people who inject heroin was to test the residue in the spoon or cooker used to prepare the shot.
Essentially, after mixing a dose of heroin in a spoon with about 1cc of water and drawing it up into the syringe, you set the syringe down and then add some more water into the spoon. Then you dip the testing strip into that secondary mixture. The idea is that due to the high sensitivity of the strips, if there were a fatal dose of fentanyl in the prepared syringe, there would be enough left in the residue stuck to the spoon that the strips would still be able detect it.
Testing this way each time you inject remains the recommended method for IV opioid users for one very important reason: the chocolate chip cookie effect. The most important thing to know about fentanyl and its analogues is that when they are mixed with other drugs, they are never mixed evenly. A pinch of heroin from one side of a baggie might contain no fentanyl at all, while a spot on the other side might contain a fatal dose. (2) Testing just one random sample from your baggie, therefore, isn’t good enough. You need to test it all, and because you can’t dilute an entire week’s worth of heroin in water and let it sit around, that means you need to test every time you inject. But at least this method allows people who inject heroin to test everything they consume without wasting anything.
The Ideal vs. the Practical
Folks who inject methamphetamine could also test this way, but testing every time you inject is difficult for someone who injects multiple times per day. This isn’t just inconvenient. At $1 – $2 a strip, it could also be a financial burden and accessibility issue. For these reasons, harm reduction workers began suggesting “second best” methods for testing, essentially testing a cross section of each new batch before you use any. Typically, this involves testing the residue inside the baggie the drugs came in, under the assumption that at least some fentanyl will remain in there if it were in the baggie to begin with. But how much should you dilute your baggie residue?
This is where the mistakes enter the picture. Even before we announced in early 2017 that our lab study revealed methamphetamine and MDMA could produce false positives, word was already going around about false positives with meth. And so to avoid false positives, harm reduction workers began advocating that people dilute meth considerably before testing it. They did this without knowing what a proper dilution actually was. Specifically, instructions began to appear telling people who use meth to test the residue in their baggie using an entire half cup of water.
This is far too much water, and I’ll explain exactly why. This section is a bit calculation-dense, so I will include translation-summaries at the bottom of each segment.
The following table is from our lab study. It shows the minimum concentration point (or maximum dilution point) needed for fentanyl and each of its analogues we tested.
[TABLE REMOVED BECAUSE STUDY IS BEING SUBMITTED FOR PEER REVIEW]
As shown by the chart, the strips require differing minimum concentrations depending on the analogue in question. These concentrations vary between 20 nanograms (ng) per milliliter of water for fentanyl itself, all the way up to 10,000ng (10 micrograms) per milliliter for sufentanil. This means that one analogue could require a presence 500 times more concentrated than another in order to be detected. (The only analogue we tested that the strips could not detect at all was alfentanil. They also could not detect U-47700, another non-fentanyl related synthetic opioid.)
Translation: Fentanyl analogues require higher concentrations than regular fentanyl in order to be detected.
So let’s do the math. A half a cup of water is 118ml. Now let’s say that we have a baggie containing 100mg of methamphetamine. Even if we crushed those crystals into a fine powder, put it back in the baggie, shook it up and poured it out, how many milligrams of meth would likely remain stuck to the inside of the baggie? 1mg maybe? Let’s say, being generous, 2mg. So we’re going to test 2mg of meth (out of 100mg total), or 2% of the contents of the baggie.
Now, let’s say there was a fatal dose of fentanyl mixed into that meth, which can be as low as 250 micrograms (mcgs) for an opioid-naive individual. But let’s say there is a high risk of death at 500mcg. Two percent of 500mcg is 10mcg, or 10,000ng. So assuming no chocolate chip cookie effect (probably a poor assumption) we are now about to test 2mg of meth residue containing 10,000ng of fentanyl. If we drop that into half a cup of water, which is about 118ml, we end up with a solution of 84.7 nanograms of fentanyl for each milliliter of water (84.7ng/ml).
As you can see from the table, this is concentrated enough to pick up fentanyl, which can be detected at concentrations as low as 20ng/ml, but at this dilution the strips won’t be able to detect any of the other analogues, all of which require higher concentrations to be detected. Some of those analogues, like acetylfentanyl, may be even more prevalent on the street than fentanyl itself. Not to mention some of them, like carfentanil, can be fatal at significantly lower doses.
Translation: If you only test baggie residue with an entire half-cup of water, you might pick up enough concentrated product to detect fentanyl itself, but not its analogues that require a higher concentration in order to react with the strips – and it’s possible that these analogues might be even more prevalent than fentanyl.
The instructions to dilute methamphetamine by adding baggie residue into half a cup of water is potentially dangerous. But it’s even more tragic because there is no need to dilute it so much to begin with. Below is a partial table from our study showing the cross-reactivity of some non-fentanyl related substances we tested, along with the concentrations needed to trigger a false positive. (3) (Note that “NEG” indicates a negative result with the fentanyl strips, and “POS” equals a positive result.)
As you can see, the D isomer of methamphetamine (symbolized by the plus signs) triggered a false positive at 10mg/ml and 5mg/ml, but not at 2.5mg/ml. What this means is that you only need to dilute meth down to 2.5mg/ml to avoid false positives. In our instructions we recommend 2mg/ml just to be a little extra cautious. And this dilution comes to only one teaspoon for every 10mg of meth, far lower than 118 teaspoons for 2mg of baggie residue. So why the recommendation of such a large dilution?
Where Did the Half a Cup of Water Idea Originate?
The truth is, I am partially responsible for this misinformation. You see, back in 2016 I participated in a harm reduction event in Grass Valley, California, organized by Annie Oak of the Women’s Visionary Council. During the event I demonstrated how to use the fentanyl test strips to test MDMA, and I suggested dissolving an entire dose (say, 100mg) into half a cup of water. This ratio works fine for detecting regular fentanyl, but we hadn’t done our lab study yet and so we hadn’t yet learned that the strips are far less sensitive to fentanyl analogues than they are to regular fentanyl.
My demonstration was video-taped and put on YouTube, where large numbers of harm reduction advocates saw it. (It has subsequently been removed, at my request.) I believe that because of this video, the “half a cup” idea became a sort of meme, spreading through word-of-mouth and social media over the last four years, which is why it keeps popping up. It pains me every time I see it, not just because I know it is wrong and dangerous, but because I feel partially responsible for it. It is my hope that this article finally puts it to rest once and for all. You can help, again, by sharing this article far and wide. Thank you.
(1) Technically, this is only true for D-methamphetamine. L-methamphetamine requires much higher concentrations (about 25mg/ml) to produce false positives. However, since it is impossible to know the ratio of D and L isomers in street meth samples, one should dilute under the assumption that the D isomer is predominant. (Meth made from pseudoephedrine typically results in 100% D-methamphetamine, while meth made from phenylacetone or P2P typically results in a 50-50 “racemic” mixture of each isomer.) As for MDMA, we only saw false positives at concentrations of 25mg/ml or greater in our study, but this was using pharmaceutical-grade MDMA. Since then we have verified that some street samples produce false positives at concentrations as low as 5mg/ml. This is why we now recommend diluting meth and MDMA down to 2mg/ml (one teaspoon of water for every 10mg of powder or crystal).
(3) Although diphenhydramine (a common cut in heroin) and lidocaine (a common cut in cocaine) can produce false positives, the concentrations required to do so are far higher than what would ever be seen in heroin or cocaine, so there’s no real worry about false positives for them.
Last month we updated the instruction sheet for our fentanyl test strips to clarify the importance of proper dilution for various drugs. We also added 10mg micro scoops to our product line, which provide an inexpensive and convenient way to measure out approximately 10mg of crushed powder if you do not have a milligram scale.