Starring Matthew McConaughey, Jennifer Garner, and Jared Leto. Rated 14A.

For Dallas Buyers Club, Matthew McConaughey lost 40 pounds and turns in a towering performance as Ron Woodroof, a Texas electrician, rodeo rider, and hard-partying stud whose luck ran out in 1985. That’s when he was diagnosed HIV-positive as a result of having unprotected sex. When doctors finally discover his condition, he is given a month to live. The slow burn of spiritual and political transformation that McConaughey gives our cowboy antihero is almost shockingly entertaining, considering the potentially downbeat nature of the material.

The apparent death sentence brings out Woodroof’s bookish side, and (in those pre-Internet days) he begins researching whatever he can find about available meds. He eventually ventures to Mexico, where an unlicensed doctor (Griffin Dunne) turns him on to less toxic—and far less expensive—fare than the AZT—a drug used to delay the onset of AIDS—that big pharm was then pushing. Later, he discovers more good stuff in Japan, China, Canada, and elsewhere, and the film’s title refers to the loose subscription outfit that Woodroof launched, much like other self-starting clubs around the U.S.

The movie is energetically directed by Canada’s versatile Jean-Marc Vallée, who made the landmark C.R.A.Z.Y. before launching international fare as different as The Young Victoria and Café de Flore. He pairs his star with an equally potent, and emaciated, performer: Jared Leto, unrecognizable as a transgender person who calls herself Rayon. A messed-up streetwalker, drug addict, and avid T-Rex fan, Rayon represents everything that is reviled in Ron’s bull-riding world, and she becomes his number-one ally in this strange new world.

Jennifer Garner is also good as a sympathetic doctor, initially paralyzed during a crisis that the medical establishment and the Reagan Administration did little to ameliorate. The film, scripted by Craig Borten and Melisa Wallack, saves its sharpest digs for the U.S. Food and Drug Administration, which dragged its heels while thousands died. This Dallas, actually shot in New Orleans, gives full-blooded faces to those who fought their way out of the shadows.