Cannabis use is becoming increasingly common among people with diabetes. A recent US prevalence study estimated that 9% adults with diabetes used cannabis in the last month, a 33.7% increase between 2021 and 2022. Nearly half (48.9%) of users were younger than 50 years.

Cannabis use is also increasing sharply among those aged 65 years or older, many of whom have diabetes and other chronic conditions. In this demographic, the perceived risk surrounding regular cannabis use has dropped significantly, even as the data tell another story — that they are particularly at risk from emergency department visits for cannabis poisoning.

As legalization continues and cannabis products proliferate, endocrinologists will likely face more patients of all ages seeking advice about its use. Yet with few evidence-based resources to turn to, endocrinologists advising patients in this area are mostly left fending for themselves.

Evidence ‘Limited’

“The evidence on cannabis is limited mainly because of its scheduling in the United States,” Jay Shubrook, DO, a professor and diabetologist at College of Osteopathic Medicine, Touro University California, in Vallejo, California, told Medscape Medical News. 

“It was declared to be a schedule I drug in the 1970s, which meant it was ‘dangerous’ and ‘had no medical benefit.’ This made it hard to access and study in human trials.” 

That will likely change soon. On May 16, 2024, the US Department of Justice submitted a proposal to move marijuana from a schedule I to a schedule III drug under the Controlled Substances Act, emphasizing its accepted medical use. If approved, the door will open to more investigators seeking to study the effects of cannabis. 

Yet, even in Canada, where recreational use has been legal since 2018 and cannabis is sold widely with government support, there are little hard data to guide practice. In 2019, Diabetes Canada issued a position statement on recreational cannabis use in people with type 1 diabetes (T1D) and type 2 diabetes (T2D). It sought to evaluate the effects of cannabis on metabolic factors and diabetes complications, as well as self-management behaviors in those aged 13 years or older.

The authors noted that five of the six studies upon which the statement was based did not consider or report the routes of cannabis administration, which have differing risks. In addition, their recommendations were based on Grade D evidence and consensus.

What Patients Are Taking

Cannabis — also known as marijuana, weed, pot, or bud — refers to the dried flowers, leaves, stems, and seeds of the cannabis plant. The plant contains more than 100 compounds, including tetrahydrocannabinol (THC), which is responsible for the euphoric “high,” and other active compounds, including cannabidiol (CBD), which by itself is not mind-altering.

Cannabis can be ingested in several ways. It can be smoked (ie, joints, blunts, pipes, and water pipes), ingested in edible form (mixed or infused into foods), and inhaled using electronic vaporizing devices (ie, e-cigarettes or vape pens).

Compounds in cannabis can also be extracted to make oils and concentrates that can be vaped or inhaled. Smoking oils, concentrates, and extracts from the cannabis plant, known as “dabbing,” are on the rise in the United States.

There are no validated or standard dosage recommendations for cannabis strains and formulations, THC/CBD ratios, or modes of administration. Therefore, the Canadian Pharmacists Association prepared a guide for finding a safe and effective dose for medical purposes. GoodRx, a website with information on prescription drug prices, says that larger doses of THC pose greater risks, noting that the potency of cannabis has increased from 4% in 1995 to about 14% in 2019.

Potential Risks and Benefits: Canadian and US Perspectives

Health and safety risks vary with each of the different ways of using cannabis for individuals with and without diabetes, depending on a host of patient- and product-specific factors.

In a recent article proposing a “THC unit” for Canada’s legal cannabis market, researchers reported that consumers lack familiarity with THC levels, don’t know what constitutes a “low” or “high” THC amount, have trouble dosing, overconsume, and commonly experience adverse health events from cannabis use.

A recent study suggested that most clinicians are similarly uninformed, with “a lack of knowledge of beneficial effects, adverse effects, and of how to advise patients,” even for medical cannabis.

Diabetes Canada takes a stab at summarizing what’s known with respect to cannabis and diabetes, stating that:

“Research on recreational cannabis use suggests it may negatively impact diabetes metabolic factors and self-management behaviors. The safety of recreational cannabis use has not been demonstrated, whereas regular cannabis use is associated with worsening glycemic control, more diabetes-related complications, and poorer self-care behaviors, such as adequate glucose monitoring, adherence to medications, and compliance with dietary and physical activity recommendations for people living with both type 1 and type 2 diabetes.”

The American Diabetes Association’s information on cannabis consists of a patient-oriented article on CBD oil. The article stated:

“There’s a lot of hype surrounding CBD oil and diabetes. There is no noticeable effect on blood glucose (blood sugar) or insulin levels in people with type 2 diabetes. Researchers continue to study the effects of CBD on diabetes in animal studies.”

It concludes that:

“Although many claims continue to be made about CBD oil, there is little evidence of any benefit. It’s certainly not an alternative to traditional diabetes management. The safety of CBD is also unknown — it may have dangerous side effects that we won’t know about unless further research is done.”

A Roundup of Recent Studies

A smattering of recent studies have touched on various aspects of cannabis consumption and diabetes.

Angela Bryan, PhD, professor and co-director of CUChange at the University of Colorado Boulder, has been evaluating cannabis use in young adults (ages 21-40 years) in the SONIC study. Bryan reported at the American Diabetes Association (ADA) 84th Scientific Sessions that cannabis users were more likely to have a lower body mass index and less likely to develop T2D. Furthermore, chronic cannabis users were less likely to have measures of inflammation and no loss of insulin sensitivity.

Another study by Bryan’s group found that CBD-dominant forms of cannabis were associated with acute tension reduction, which might lead to longer-term reductions in anxiety. Bryan said the findings could be relevant in the context of diabetes distress.

Similarly positive results were found in a 15-week, double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD spray for neuropathic pain among treatment-resistant patients. The investigators reported that “clinically important improvements” were seen in pain, sleep quality, and subjective impressions of pain. Another small study of inhaled cannabis in treatment-refractory patients found a dose-dependent reduction in diabetic peripheral neuropathy pain.

Findings from a 9-year longitudinal study of approximately 18,000 Swedish men and women suggested no association between cannabis and subsequent T2D development after controlling for age, although these authors also called for longer follow-up and more detailed information about cannabis use to make “more robust” conclusions.

On the other side of the spectrum, a “rapid” review of recreational cannabis use in people with T1D and T2D found that recreational cannabis use may negatively impact diabetes metabolic factors and self-management behaviors and may increase risks for peripheral arterial occlusion, myocardial infarction, and renal disease. However, the authors cautioned that more robust research is needed to confirm the potential impact of cannabis on diabetes.

How to Advise Patients

When Shubrook was working with patients with diabetes in his family medicine practice in Ohio, cannabis wasn’t legal. 

“‘Don’t ask, don’t tell’ was the way we handled it then,” he said. 

By contrast, in California, where he’s currently located, “it’s pretty well accepted and legal, and patients volunteer information about use, even if it’s recreational,” he said. “Realizing this was something we could talk about was really eye-opening to me.” 

Talking to patients about cannabis use is a “20-minute conversation that details what they’re doing,” he said. He proceeds by asking questions: Are you using for recreational or medicinal purposes? What do you take? What do you take it for? Does it work? 

“People will tell you,” Shubrook said. “They know exactly what it works or doesn’t work for and how it affects their glucose control, which in most cases is only minimally.”

He tells patients he would prefer they don’t inhale cannabis, given the risks posed to the lungs. 

“Edibles may have a slower onset of effect, but depending on what they’re adding it to, glucose might be affected,” he noted. “And I have seen that chronic use can lead to hyperemesis syndrome.”

Overall, he said, “Take the time to talk to your patients about cannabis — it will allow them to be honest with you, and you can improve the specificity and safety of its use. If cannabis is legal in your state, encourage people to go to legal dispensaries, which will reduce the risk of it being laced with another drug that could increase the danger of use.”

A recent US prevalence study found that people with diabetes who use cannabis likely engage in other substance and psychoactive substance use, including tobacco use, binge drinking, and misuse of opioids and stimulants. 

“Use of these additional substances could further exacerbate the health risks associated with diabetes and also emphasizes the importance of addressing polysubstance use among adults with diabetes,” the study’s author Benjamin H. Han, MD, Division of Geriatrics, Gerontology and Palliative Care, Department of Medicine, US San Diego School of Medicine in La Jolla, California, told Medscape Medical News.

“We were surprised at how strong the associations were, especially with use of substances that can increase cardiovascular risk,” Han added. “And given the strong association we found between cannabis use and use of other psychoactive substances in diabetes, clinicians must screen all their patients for psychoactive substance use.” 

Diabetes Canada’s position paper states that despite the limited evidence, “there were sufficient data to begin developing recommendations for type 1 and type 2 diabetes about education, counseling, and management related to recreational cannabis use.” 

Their recommendations include the following:

1. Healthcare professionals should engage their patients in discussions about substance use on a regular basis, with a nonjudgmental approach.
2. The use of recreational cannabis is not recommended for adolescents and adults with diabetes.
3. People with T1D should avoid recreational cannabis use because of the increased risk for diabetic ketoacidosis.
4. For adults with T1D or T2D who intend to use cannabis recreationally, individualized assessment and counseling should be offered to inform them of the general risks of cannabis, with a focus on harm reduction and reduction of the risk for potential adverse effects on diabetes management and complications.
5. People with T1D or T2D should be offered education on and encouraged to read public information available through resources from various Canadian health authorities about the general risks of cannabis use to reduce the risk for nondiabetes-related adverse effects of cannabis consumption.

Of note, in 2018, the Canadian government produced an exhaustive compendium of information on cannabis for healthcare professionals that includes information relevant to managing patients with diabetes. 

Shubrook and Han reported no competing interests.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.