Koons, 23, returned haemoglobin values that slightly exceeded safety limits permitted by the Federation International de Ski (FIS) in a standard pre-competition test yesterday.
Chef de Misson Peter Wardell says Koons has been training at altitude and may have been slightly dehyrated at the time of testing. These factors can increase haemoglobin levels.
Wardell said he felt for Koons. "He has made significant improvements in his performance over recent months and it terribly disappointing for the young athlete. It is important to remember, however, that these rules are made to protect athlete health and well-being."
The ruling was made by FIS. The limit is 17 g/dl and Koons tested above that with a value of 17.2 g/dl. Increased levels of haemoglobin can increase chances of thrombosis and other medical issues.
Koons will miss two of his four Olympic events but, subject to a new test, will compete in the 30km Pursuit on 20 February and the 50km Mass Start on the 28th of Feb. These latter two races are his preferred distances.
The New Zealand Olympic Committee medical team will now work with the athlete to ensure Koons' haemoglobin returns to a safe level.
Two other cross country skiers at Vancouver 2010 have been stood down for exceeding haemoglobin limits.
This stand-down is NOT a sanction but is instituted to protect the health of the athlete.