I commenced on a walk up into the Himalayan mountains. After 5 hours climbing I began to feel shocking. I spent the night In Rumbak (Ladakh) and in the morning, still feeling lousy, decided not to continue the walk, but to descend. On reaching Leh, I attended the SNM Hospital where I was diagnosed with HACO, treated, released and advised to evacuate to a lower altitude. I have documentation from Leh Hospital, and the CC slip from Malaysian Airlines in Delhi