The Mile-High City took Lady Gaga‘s breath away.
Gaga was hospitalized late Wednesday after her Denver concert at the Pepsi Center due to altitude sickness, People reports.
She posted a selfie on Instagram wearing an oxygen mask and full concert makeup, warning her fans that altitude sickness is for real.
“Altitude Sickness is no Joke! #hitThatHospitalS—t #artRaveDenver many true ravers crowd tonight,” she wrote.
The “Applause” singer is in the middle of The ARTPOP Ball world tour and is scheduled to perform as planned in Seattle on Friday.