My cardio did not hand me a study.  He just determined the dose for my size/weight. Here is one that is 4 days old:  https://www.healthline.com/nutrition/how-much-vitamin-d-is-too-much This is the D study: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108 This is a boring video I'm watching on Celiac.    

Can you link the 2019 JAMA study? When you say "massive doses of D" how large are you talking about? 

Thank you.  I'll run it by him on my next visit.  

Yes, Yaya, it is possible to develop vitamin D toxicity with overdosing since it is a fat soluble vitamin but the dosage needed to get to that point is much larger than was thought years ago. Years ago, doctors were very cautious about D supplementation but more recently the medical community has relaxed their caution as it proved to be overdone. Individual practitioners are not always up to date on everything and sometimes are operating on dated information.