Lady Gaga hospitalized with altitude sickness

Lady Gaga arrives at her "Cheek to Cheek" taping at Lincoln Center on July 28, 2014, in New York.

Jamie McCarthy/Getty Images

We've seen Lady Gaga with plenty of masks and accessories over the years -- but none quite like this.

The 28-year-old pop star posted a selfie from a hospital bed while donning an oxygen mask late Wednesday, noting that she was hospitalized for altitude sickness after her concert in Denver.

"Altitude Sickness is no Joke!" Gaga wrote in the caption on Instagram. "#hitThatHospitalS--t #artRaveDenver many true ravers crowd tonight."

Gaga's next stop is Friday in Seattle. Let's hope her flight to the state of Washington is a little easier.