Key safety tips as legal medical and recreational marijuana evolve.

Multicolored graphic squares with icons for canabis products like edibles, topicals, tincture, tea, and prescription bottle

It’s fair to say that society’s views on cannabis have been evolving. Today, adult recreational use is legal in 21 states and medical use is legal in most other states, to varying degrees. The use of cannabis doesn’t seem to be going away. Given that, here is what you need to know to make using cannabis safer.

Buy it legally

If you live in a state with legal cannabis — whether medical or recreational — go through the legal market rather than the illicit market, despite the temptation of lower prices. While many state programs are less than perfect, buying cannabis through the legal market generally offers some advantages and protections:

Some things to watch out for in the legal market:

Pay attention to potency

The most straightforward way to get into trouble with cannabis is by consuming too high a dosage of the main active ingredient, THC. As with any medicine or drug, it is safest to use the lowest effective dose for the shortest time permitted.

Cannabis flower is far more potent than it was back in the 1970s. People who haven’t used cannabis in the modern era may inadvertently overconsume, assuming it is the same weed that they had back in the day.

Taking too much cannabis, or using cannabis that is too strong for you, can cause a severe anxiety attack, possibly landing you in the emergency department. You do not want this! Too high a dosage can also potentially trigger other medical conditions, such as cardiac arrhythmias and syncope.

Some people develop cannabis hyperemesis syndrome — uncontrolled vomiting in response to cannabis use — which can only be treated by ceasing use. Start low, go slow, and stay low is good advice, especially if you’re new to (or newly back to) using cannabis. Be careful with all edibles, especially any you make yourself: licking batter off the spoon means you’re consuming the marijuana.

Concentrates (called wax, shatter, or crumble) feature extremely high levels of THC. They often don’t have other medicinal cannabinoids such as CBD, which can mitigate some of the unwanted effects of THC. It is much easier to overconsume with these concentrates, as the THC content ranges from 40% to 90%.

Who should not use cannabis?

As with all things in medicine (including medical cannabis), there are exceptions to all rules, but generally:

If you are having trouble controlling your cannabis use or if you find it is escalating, seek professional help.

What else to know

About the Author

photo of Peter Grinspoon, MD

Peter Grinspoon, MD, Contributor

Dr. Peter Grinspoon is a primary care physician, educator, and cannabis specialist at Massachusetts General Hospital; an instructor at Harvard Medical School; and a certified health and wellness coach. He is the author of the forthcoming book Seeing … See Full Bio View all posts by Peter Grinspoon, MD

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