There is no single American drug supply. There are at least four — and each one has its own chemistry.
The national overdose conversation tends to talk about “the drug supply” as if it were one thing — a single, uniform market that occasionally shifts under everyone’s feet at once. The samples don’t look like that. When you actually test what people are using, in city after city, the supply splits into regions, each with its own chemistry, its own cuts, its own emerging adulterants.
Of 90 substances we detect routinely, only 20 turn up everywhere at similar rates. The other 70 are concentrated. Some are 80 or 90 percent confined to a single region. The North American supply isn’t one market — it’s four overlapping ones, and the patterns repeat themselves over years of sampling.
If you build national policy on a national average, you will be wrong everywhere at once.
This matters because nearly every tool we have for responding to the overdose crisis is local — local outreach workers, local harm reduction programs, local emergency departments, local drug checking services. The questions those programs ask are not national: what is in our supply right now? What new contaminants should our test strips detect? What should our naloxone training mention? A national figure that says “xylazine is present in 8% of fentanyl samples” collapses a Northeast where it’s closer to half into a West Coast where it’s almost absent. Both of those programs need different things.
The UNC Street Drug Analysis Lab runs an anonymous, mail-in drug checking service. Harm reduction programs, clinics, hospitals, EMS, syringe service programs, FTIR drug checking partners, and community organizations across the United States send us de-identified samples — most often residue from used baggies, cookers, or paraphernalia — and we return a detailed analytical report identifying the substances present. We use gas chromatography–mass spectrometry (GC-MS) for confirmation, with quantification on a subset.
The data shown here cover the period January 2022 through April 2026 — over four years of continuous sampling, comprising tens of thousands of analytical results from samples collected across all four U.S. Census regions. For each of 90 substances we computed two quantities per region: a rate per 1,000 samples (how often the substance appears in that region’s submissions) and a regional share (what fraction of all national detections of that substance came from each region). The bars below show share; the tooltips show both.
A note on the sampling: this is not a random sample of the U.S. drug supply. We see the supply that reaches harm reduction programs and drug checking partners. That coverage is uneven — strong in some states, thin in others — and the populations we serve are not the same as the general population that uses drugs. What we map here is the reachable supply: what reaches the people most likely to be harmed by it. That is, in practice, the supply that public health needs to know about.
Each of the 90 substances has been sorted into one of five groups based on how its national signal is distributed:
A substance is assigned to a regional cluster if a single region holds at least 35% of its national signal. The 20 substances where no region exceeds that threshold are grouped as ubiquitous — they saturate the supply nationwide.
Browse the 90 substances by cluster below. The dominant region’s bar is bold; the other regions are shown lighter so you can still see the full distribution. Hover any tile for the rate per 1,000 samples and the precise share. Use the heatmap toggle for a denser one-screen view, or filter by region or substance name.
The Northeast cluster is dominated by substances you only see in significant quantities where cocaine is widely used and locally processed. Phenacetin and procaine — both at 82% Northeast — are classic cocaine cutting agents. Tetracaine, another local anesthetic used as a cocaine bulker, follows the same pattern. The Northeast also leads on emerging sedatives: medetomidine, the veterinary alpha-2 agonist now spreading through the East Coast fentanyl supply, sits at 62% Northeast in our data. Novel benzodiazepines like N,N-dimethylpentylone and bromazolam show up here too. This is the supply chain that runs through Philadelphia, New York, Boston — old port cities with deep cocaine markets, now sharing distribution networks with newer synthetic adulterants.
The Midwest stands out for a single dramatic anomaly: diphenhydramine (Benadryl) at 89% Midwest. This is not a national trend. Something about supply chains in the Midwest — probably involving specific source materials or cutting practices — concentrates this sedating antihistamine in fentanyl samples here and almost nowhere else. The Midwest also leads on protonitazene (a potent synthetic opioid in the nitazene family) at 64%, and on traditional cuts like quinine, niacinamide, and erythritol. The diphenhydramine signal in particular is a regional drug checking priority that a national average would completely miss.
The Southern cluster is heavy with substances that mark cocaine product as less refined or more heavily adulterated. Norcocaine, tropacocaine, and N-butyl-aniline are byproducts of less-thorough refinement; phenethyl chloride appears at 100% South in our data; sugar cuts dominate. One reading of this pattern is supply-chain economics, not geography: the Northeast cocaine market pays the highest per-gram prices in the country, and higher-purity product gets routed there. Less lucrative regional markets — including much of the South — receive product that has been cut more aggressively, or that wasn’t cleaned up in the first place because the price point didn’t justify it. The chemistry doesn’t tell us where the product was made; it tells us what tier of the market it was destined for.
The West Coast supply has its own distinctive signature. Aniline (84% West) and noramidopyrine (88% West) are markers of a different fentanyl synthesis pathway than what dominates the East. NPP — N-phenethyl-4-piperidone, a key fentanyl precursor — also concentrates here. The West is where you find 2C-B and other classic psychedelics at meaningful rates. And heroin, increasingly rare nationally, still shows up at 59% West — a residual signal from a market that fentanyl has otherwise overrun.
Twenty substances saturate the supply nationwide. Fentanyl and 4-ANPP (its primary synthesis precursor and degradation product) sit at almost exactly 25% in each region — the textbook definition of evenly distributed. Methamphetamine tilts slightly West (33%) but is everywhere. Lidocaine is used as a cut nationwide. These are the substances where national policy actually applies, because the supply really is national. Everything else demands a more local lens.
The substances that dominate a region’s supply often aren’t the substances people are looking for. They are the substances people are getting anyway.
Three implications follow from this map.
One: drug checking infrastructure needs to be regional, not centralized. A single national lab, however well-resourced, will tend to flatten regional signals. We need lab capacity distributed across the country so that emerging adulterants — the next medetomidine, the next nitazene — get caught quickly in the regions where they actually emerge.
Two: harm reduction tools have to be tuned locally. Test strip programs, naloxone formulations, overdose prevention training, and emergency department protocols all benefit from knowing what is actually in the local supply. A program serving rural North Carolina has different priorities than one in Philadelphia or San Francisco, and the data show it.
Three: federal scheduling decisions should weigh regional concentration. When Congress considers scheduling a substance, the national prevalence number is often the headline. But many of these substances are 70 to 90 percent concentrated in a single region, which means their scheduling implications — for diversion, for legitimate medical supply, for downstream replacement adulterants — play out very differently in different parts of the country.
Drug checking, as a method, sees what gets sent in. Samples come from harm reduction partners and people who already have relationships with services, which means our coverage is denser in some places than others, and skewed toward the populations our partners reach. We are also, by design, looking at substances we know to look for — the 90 substances here are the ones our methods reliably detect; new molecules require the analytical work to add them to our panel before we can report on them. And we report regional aggregates here, but inside each region there’s further variation — Philadelphia is not Boston is not Pittsburgh, and the patterns shift block by block in ways this map can’t show.
What we can say with confidence: the supply is not uniform. It hasn’t been for years. And the longer we treat it as if it were, the more we will keep responding to last region’s crisis instead of the one in front of us.