DIYers purchase the raw materials, active pharmaceutical ingredients of mysterious origin and unknown safety, online, with no prescription necessary. While these materials carry warning labels -- "for research only" or "not allowed for use in humans" -- that hasn't stopped people like Carlos Alvarez, 58. He moderates an internet forum devoted to the search for sources of tirzepatide, the active ingredient in the blockbuster drug Mounjaro. At his home in Phoenix, Arizona, Alvarez reconstitutes freeze-dried tirzepatide powder with sterile water, creating a solution that he injects under his skin.

Alvarez, who has prediabetes, felt frustrated that his insurer wouldn't cover Mounjaro, the drug that he determined would be the best remedy for his high blood sugar levels. The cost, he says, was "astronomical." Wanting to avoid "the mercy of a medical system that I feel has left me without help … I went the full DIY route. It's in my nature anyway."

But experts say what Alvarez and others are doing poses many risks.

"It's not safe to make it in your kitchen. It's just not safe at all," says Stephanie Young Moss, PharmD. Dr. Young Moss is a trained pharmacist and healthcare consultant. While she acknowledged that "people are desperate" for the game-changing anti-obesity drugs, she expressed suspicion of any vendor who would sell drugs marked "for research only" directly to consumers.