If Harry Potter turned into a vampire while at Hogwarts in fanfiction, his social life would be turned upside down. The other students would likely be both fascinated and frightened by him. He might be ostracized by some, but also gain a following of those interested in the dark and mysterious. His studies would need to be adjusted as well. He'd have to learn about vampire lore and how it relates to magic. His access to certain areas of the castle might be restricted, especially if the school feared he could lose control. He'd have to constantly battle the urge to feed, which could put him in dangerous situations around his classmates. And his role as 'the boy who lived' would be overshadowed by his new identity as a vampire.
His classes would be a struggle. For example, in Potions, the smell of the ingredients might be overwhelming to his new vampire senses. And in Defense Against the Dark Arts, he might have a new perspective on dark creatures since he is now one of them.
His diet at Hogwarts would be a major change. Instead of eating normal food, he would need blood. He might have to find some discreet way to get it. His sleeping habits could also be different. And he would probably be the center of a lot of rumors and fear among the students.
He'd likely have to keep his vampire identity a secret. He might not be able to participate in some daytime activities or classes that take place outdoors during the day. His diet would be a huge issue, having to find a way to get blood without being discovered.
His relationships would likely be very different. For one, he might be more of an outsider. The other students grew up in the wizarding world in a more common way, while Harry was raised by the Flamels. He could be seen as having an unfair advantage in terms of magic knowledge. But on the other hand, he might also be respected more for his unique upbringing.
In terms of his classes, Defense Against the Dark Arts would be a whole new experience. He could use his Saiyan powers to counter dark magic in ways that no one has ever seen before. He might even develop his own unique spells that are a blend of magic and Saiyan energy, making him a truly formidable wizard - Saiyan hybrid at Hogwarts.
He'd be more in touch with nature. His magic could be centered around life - based spells.
His life would be much quieter. No more noisy Gryffindor common room or bustling Diagon Alley. He could enjoy the peace of nature, listening to the wind in the trees and the calls of magical birds.
His life would be very different. For one, he'd have to deal with the extreme cold. Magic would be used in different ways, like creating warm shelters or finding food in the harsh winter. Also, he'd be far from his friends in Hogwarts, so he'd have to make new friends, maybe among the local magical folk or other outcasts who live in Alaska.
He'd be more technologically inclined. Since Wakanda is known for its advanced technology, Harry might integrate magic with tech more often. For instance, he could use Wakandan communication devices enhanced with magic for long - distance spells.
If Harry had diabetes in fanfiction, his social life might change. He might be more cautious about going on long outings with friends. For example, when they plan a trip to Hogsmeade, he has to make sure he has everything he needs. Also, his confidence could be affected. He might worry about being a burden to his friends during dangerous situations like facing Death Eaters, because his diabetes could potentially slow them down. And his relationships with teachers might become more complex as they try to accommodate his condition while still maintaining the standards of Hogwarts.
His life would be completely different. He'd be part of a vampire society instead of the wizarding one. He'd have to adapt to their nocturnal lifestyle.