On 1 July 2013, it was announced that Carter had been diagnosed with testicular cancer. He had surgery a day later and was advised to rest for a month. On 19 July 2013, he announced on his Twitter page that he had received the all-clear and would resume his career at the Shanghai Masters in September. He stated in April 2014 that he would have chosen to take six months to a year away from snooker, but this had not been possible due to his need to regain his place in the top 16 of the world rankings. A month later, World Snooker announced that Carter had been diagnosed with cancer in his lung and would be taking a break from the sport to receive a course of intensive chemotherapy. In August 2014, he successfully completed treatment for this secondary tumour (metastatic recurrence of the testicular cancer), including surgery, and returned to the World Snooker Tour in October at the General Cup, which he won.