I had a random blood test and my Vitamin D level was through the floor. I had high dose Vit D and blood tests to monitor this and and catch any spike in calcium blood levels.
It went back to normal levels and I supplement daily.
I researched this and there is a medical paper on it, some people on warfarin were found to have dramatically low vitamin d, some borderline, some unaffected. The patient study overall suggested that ⅔ of warfarin users vitamin D levels were reduced moderately to severely.
Takeaway is, if on warfarin, request a blood test to check your vitamin levels.
I'm now on a doac but still supplement D3.