Union Cycliste Internationale (UCI) will ban the repeated use of carbon monoxide (CO) inhalers from 10 February.
It will only be allowed within a medical facility and under the responsibility of a medical professional. The decision was taken at a UCI executive committee meeting in France on Saturday, alongside the 2025 UCI Cyclo-cross World Championships, which were held in Liévin.
As a reminder, CO is commonly used in sports medicine to measure total haemoglobin (Hb) mass and blood volume, especially to examine the effects of endurance training and altitude exposure on oxygen carrying capacity. However, its repeated inhalation can result in acute and chronic health problems, for example headaches, lethargy, nausea, dizziness, and confusion. Such symptoms can worsen at any time and develop into problems with heart rhythm, seizures, paralysis, and loss of consciousness.
The new regulation forbids the possession, outside a medical facility, of commercially available CO re-breathing systems connected to oxygen and CO cylinders. This ban applies to all licence-holders, teams and/or bodies subject to the UCI Regulations and to anyone else who might possess such equipment on behalf of riders or teams.
The inhalation of CO will remain authorised within a medical facility and under the responsibility of a medical professional experienced in the manipulation of this gas for medical reasons and in line with the following restrictions: only one CO inhalation to measure total Hb mass will be permitted. A second CO inhalation will only be authorised two weeks after the initial Hb measurement.
For riders in UCI WorldTeams, UCI Women’s WorldTeams and UCI ProTeams, any CO inhalation for the purpose of determining total Hb mass must be recorded in the medical file established for each athlete, in compliance with Articles 13.3.020 to 13.3.026 of the UCI Medical Rules.
The UCI’s ban is independent of the World Anti-Doping Code and the UCI Anti-doping Regulations, however the UCI has officially requested the World Anti-Doping Agency (WADA) to take a position on the repeated use of CO in and out of competition.
