Health Minister Andrew Little conceded in May that the medicinal cannabis regime isn't working, but he's refused to bring forward a review at the end of the year to fix it.
They also can't be sure what they're taking is what they think it is without breaking the law.
Now a bill before Parliament has the potential to reduce drug-related harm for these thousands - or tens of thousands, according to some estimates - of people, even though that isn't the problem the bill was sold as fixing.
A drug-checking law was passed before last summer so that festival-goers could get their drugs tested to see if they were what they were thought to be.
The harm-reduction value from drug-checking service KnowYourStuffNZ is clear.
One-third of what was thought to be MDMA that was tested this past summer was mostly eutylone, a much more dangerous substance; 68 per cent of people said they wouldn't take a substance that was different to what they thought it was.
Drug-checking services also do not increase the use of illegal drugs, according to a November 2020 report by Victoria university Associate Professor Fiona Hutton.
"It does not encourage those who don't use illegal drugs to start using them. Behaviour change is evident when substances are not as sold. Harm-reduction advice is valued and acted upon by young people," Hutton's report said.
The law expires at the end of the year, and the bill replacing it has the potential to step into the medicinal cannabis void that the Government so far has feared to tread.
Legal medicinal cannabis remains too expensive for most patients, costing up to $1000 a month, meaning last year's cannabis referendum has left behind an ongoing black market, supplied by so-called "green fairies".
A recent ESR study that tested 100 green fairy samples found "a wide range of cannabinoid concentrations and the claim that a product was high in CBD was often not correct".
"The proposed dose size was not specified for these products, but few would provide what is considered an effective dose when compared with the administration of commercially purified cannabinoid products available by prescription."
KnowYourStuffNZ uses spectrometers, which cannot check for cannabinoids, but that's where Grant Hoey, an Auckland commercial property businessman, wants to step in.
"You can imagine people who are very ill - they are vulnerable, and they are desperate. We can tell them very accurately if they're taking bad substances," he told the Herald.
"Green fairies are only working on what the seed suppliers told them or what the grower told them, which can be inaccurate. There's a massive need for a patient harm-minimalisation."
Hoey became interested in medicinal cannabis years ago after his wife's mother, suffering from debilitating migraines, was made worse from "mainstream medicines".
"She looked at some of the cannabinoid medicines and, over time, she's got back a much better quality of life."
He says he spent lockdown last year researching different devices before buying a $50,000 high-performance liquid chromatography instrument.
"I can detect and quantify cannabinoids in medicines that are homemade to let patients know what's in them, and also what harmful substances there might be including plant growth regulators, weed sprays and heavy metals.
"And that's what I'm aiming to do."
He has already tested legal Tilray products, and his instrument has shown the same contents as on the products' certificate of authentication.
And the Health Ministry is taking notice.
"I've been invited to Wellington to do a live presentation for Health, Police, Customs, KnowYourStuffNZ, so they can see what an instrument of this type is capable of."
His service would need to be licenced - which would be at the discretion of the director-general of health - following the passage of the bill, which is currently at select committee.
The bill would mean that an individual, such as a green fairy or one of their patients, could pass their medicine over and a licenced service could check it without breaking the law.
The committee should already be aware of the potential of the bill in the medicinal cannabis space.
"Legal drug checking will allow patients to test products for a range of cannabinoids, their relative strengths and any unwanted extras, such as moulds and pesticides," the Drug Foundation's submission on the bill says.
What remains to be seen is whether the Government will want the bill to enable such services in the medicinal cannabis space.
It wouldn't resolve many of the Government's stated goals in drug law reform, including not criminalising drug users unless it's in the public interest, making legal medicinal cannabis affordable for those who need it, and ensuring equitable access to drug-checking services.
But it aligns with Prime Minister Jacinda Ardern's rhetoric about treating drug use as a health issue.
And it would allow her an extra harm-reduction badge on her blazer in an area where the Government has said its hands are effectively tied by the referendum result.