The reality TV star is scaling Macchu Picchu in Peru - a 15th century Inca site located in the South American country.
Despite preparing for the climb both mentally and physically, the 25-year-old posted a photo of himself early today (4 March), with the caption: "Finally in Cuzco and I'm not going lie it's hard to breath already!"
Earlier in the day, he posted a map of Peru, with someone from his team writing: "Kirk travels to Cuzco today, altitude is 11,000 ft -1st testing day for Kirk as he deals with altitude changes!"
Until now, Kirk has remained very positive about his challenge, where he is hoping to raise thousands of pounds for the ADHD Foundation.
He posted a photo of himself giving the thumbs up, and wrote: "Lovin Peru!!"
To sponsor Kirk, visit www.virginmoneygiving.com/kirknorcross