Everyone's worried about fentanyl-tainted methamphetamine supplies, and deservedly so; people taking a stimulant who didn't expect to take an opioid do end up in trouble.
However, research into fentanyl adulteration is starting to reveal that there is a lot of variation on how much it's a problem, based on temporal, ethnographic and geographic factors. Here's an interesting recent paper that showed that geography made a particularly high impact in fentanyl urine positivity in meth users : positivity was nearly twofold as high in New Mexico vs. Nevada (68 vs. 32%). It also showed that fentanyl exposure in this population was disproportionately high in Hispanic users (60% vs. 40% non-Hispanic users), revealing this population to be particularly at-risk of unintentional fentanyl overdose.
The study's main goal was actually to investigate whether methamphetamine users could tell if they were taking fentanyl when taking methamphetamine, and found that they generally did--if the participants said they didn't use fentanyl, they were right 93% of the time; if they said yes, they were right 99% of the time. This is reassuring in that it may reflect increasing familiarity and knowledge of the risks of fentanyl adulterated supplies.