A dosing mechanism for fuels, particularly for the input into a chemical reformer to obtain hydrogen, has a metering-in device for metering fuel into a supply line, which opens out at at least one dosing aperture into a transporting line transporting a tempered material flow. A holding device for accommodating the metering-in device has an insulating body which thermally insulates the metering-in device from the transporting line that transports the tempered material flow.