Lady Gaga spent some time in a hospital last night following her show in Denver. It turns out the singer had a tough time adjusting to the mile-high altitude of the city and needed to be treated for "altitude sickness."

Gaga posted a selfie on Instagram showing her with an oxygen mask over face. She posted, "Altitude sickness is no joke." It's also not so uncommon for people visiting Colorado. Symptoms of altitude sickness include things like fatigue, shortness of breath and headaches. Her next show, scheduled for tonight in Seattle will go on as scheduled.

 Get well Mother Monster! She wasn't all glammed out like she now. Peep these pics of Throwback Lady Gaga: