Draco had told Hermione and this had caused both of them to notice the discrepancies in Harry's behaviour and patterns, and when they began noticing several oddities they began to suspect that potions were involved as well. Hermione wanted to take him to the healers in St. Mungos, but Draco suggested taking him to goblin healers, as they wouldn't talk to the media and, most importantly, their results could not be tampered with. He asked Harry for "help" finding something in his vault as a gift for Hermione, as he needed a reason to get him away from the Weasleys, and took him to Gringotts. He had previously procured an appointment for Harry and the procedure took place. 