For the first session with the doctor, it is strongly recommended to have an appointment face-to-face with them, but after the first appointment, if the doctors agree you can have an online call to talk about the tests, how you feel, if you think the doses have to be increased, your calcium levels, the PTH levels etc. It is what I do with my doctor.

I usually have two appointments per year. It is enough for me because my doctor already gave me the correct Vitamin D3 dose, and the tests I do every six months have been showing I am within safety limits of calcium in blood