Can a test of hair loss caused by vitamin d deficiency be reversed?

In  my opinion, hair loss from vitamin D deficiency may be reversible. There are two types of associated hair loss. Telogen effluvium and alopecia areata. TE is usually reversible. However, If the telogen effluvium unmasks an androgenic alopecia, it may be more difficult to regrow  hair. Limited Alopecia areata is usually reversible with treatment. Find a hair loss expert and establish a diagnosis. Develop a treatment plan. Most likely you should be able to reestablish hair density.
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There is rarely a case of hair loss in my opinion that is truly and solely due to a deficiency of vitamin D. It does occur but it is not very common. Yes, Vitamin D levels can come back low.  In fact, they often do. But there has never ever been a study definitely showing improvement of hair with vitamin D replacement alone - nor do I see it all that often. I see hundreds upon hundreds of patients with vitamin D deficiency. I think it's important to replace it to give other treatments a better chance of working and to possibly slow hair loss. However taking vitamin D alone with the hopes to improves one's hair rarely proves useful.

Hair loss from a Vitamin D deficiency may reverse if you give it at least a year; however, if you have underlying genetic hair loss, then the reversal may not occur