Hi, a few papers here to read, if you feel your D could be low, do talk to your GP and or main consultant by phone or video, to get their advise on increasing your dose if appropriate, or taking it under the guidance of your specialist or GP if not on it.
ncbi.nlm.nih.gov/pubmed/322...
bmj.com/content/369/bmj.m15...
In addition Vit C has found to be useful, and it appears to be written up that a dose which does not exceed. 1000 mg is ok with Warfarin, but above that can cause a problem. However do still check with the GP and consultant, also a good idea to split the Vit C dose into twice a day rather than all at once. MaryF