Vit d 600 K Injection

So i have been in the range of 25 nmol/L for Vit D and was suggested to take a 600 k injection by the doctor which i have. I have the following questions

1.Is it necessary for me to take Vitamin k now and during maintenance phase with these levels(Doc said not needed)..My Magnesium levels are low so i am taking Magnesium Glycinate daily for 30 days.

2.How long would the injection suffice to keep levels higher?

3.Thereafter what dosage should i take( and what would be better daily or monthly ? I plan to take it for life without stopping as i do not get any sunshine and my levels are of <30 are standard for me.