The invention describes an illuminant for a vehicle headlight comprising a carrier and an electrical driver. Mounted on the carrier are a high-beam LED, a low-beam LED and a vehicle light detector. Additionally, a mechanical interface is included for mounting the illuminant in a corresponding socket of the vehicle headlight in a detachable way, and an electrical connector for supplying electrical power to the electrical driver. The electrical driver is arranged to receive vehicle light detection signals from the vehicle light detector to determine vehicle light by means of the vehicle light detection signals, and to provide a drive current to the high-beam LED or the low-beam LED depending on the determined vehicle light. Illuminant is further arranged to detect ambient light other than the vehicle light, such detection of ambient light influencing electrical driver in controlling the LEDs.