We were in MP in 2016 and I have asthma. I agree that you should check with your own doctor about any health issues you may have before you go. We were a party of four, two of us had issues and two did not but not bad enough to require medical intervention. We did bring an over the counter Altitude Sickness med which worked for the two of us. We planned for a week to explore not only Machu Picchu (amazing!) but the surrounding countryside. The best thing we did was contract with Kuoda Travel to take care of us for the week. Our fantastic guide Katarina made sure our pace never stressed