I'm a 20-year-old female with bald spots, what should I do to regrow my hair?

I recommend getting a formal evaluation with a hair loss expert to go over your condition and advise you on best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

I'd suggest seeing a physician who can diagnose what exactly is the cause of your bald spots.  Without a photo, it's not possible to diagnose the cause of your hair loss. Biotin, calcium and vitamin D do not have proven benefit is most types of bald spots. Seek advice on the correc diagnosis.

Lichen pilanoplaris, frontal fibrosing alopecia, central centrifugal cicatricial alopecia, psudopelade, chronic cutaneus lupus erythematosis,follicularis decalvans, tufted folliculitis, dissectindg cellulitis, keloidal folliculitis are some types of autoimmune cicatririal alopecias besides fungal diseases that may cause patchy hair loss as alopecia areate.  So you may need to have a full exam with an hair surgeon, dermatologist and skin biopsy to find out reason for hair loss.