Is It Safe To Take Arachitol And Vitamin D3 Supplement Together?

I was told by a doctor that Arachitol 6L is enough for one year and I need not to take any other D3 supplement for one year and can take again the Arachitol 6L that will be enough for the coming year and so on. Is that correct? Do I still need to take vitamin D3 supplement and in what doses and how long/