Altitude Sickness begin to appear at (aproximately) what altitude??

Question

If someone that lives near or at sea level climb, for example, climb to Munich(1700ft or 520m), Saskatoon(1890ft or 580m), or Oklahoma City(1200ft or 400m), the chances of altitude sickness are very very rare, if nonexistent.In other hand, if this person climb, to La Paz(11940ft or 3640m) or Cuzco(10860ft or 3310m), some form of altitude sickness is surely expected, no??In places like Mexico City(7350ft or 2240m) or Addis Ababa(7725ft or 2355m), through rarer, its not totaly unexpected, and still occurs with some frequency.But...what about someone from below, lets see, 1700ft, that climb to cities between aproximately 3400ft-6800ft, such as Colorado Springs(6030ft, or 1840m), Calgary(3440ft or 1050m), Denver(5280ft or 1609m), Johannesburg(5750ft or 1750m) or Salt Lake City(4230ft or 1290m)???There's some kind of altitude sickness at these "moderately-high" altitudes???At what altitude, aproximately, people from sea level start having trouble in adjusting to the new height??

Answer 1

It differs per person. One person may get it at 6000 feet and another not might get it at all. It just depends who you are, what altitude you're normally at, and what altitude you're at at the moment.

Answer 2

Jackalope is right.  When I go backpacking every year in the Sierra Nevadas, I start feeling affects of altitude sickness at 13,200 feet.  My brother doesn't get it at all, and another buddy starts getting it at about 12,700 feet.  I live at sea level, my brother lives at about 800 feet above, and my buddy lives at 500 above.  I hope this answers your question.