Rocky mountain too high!

Lady Gaga fell victim to altitude sickness and had to be hospitalized after her concert in Denver on Wednesday, and she decided to share a selfie while wearing her oxygen mask!

"Altitude Sickness is no Joke! #hitThatHospitalS--t #artRaveDenver many true ravers crowd tonight," she captioned the photo.

Even though she was under the weather, she still looked gorg like a true pop diva!