I was diagnosed with both severe (i.e., total) vitamin D deficiency and parathyroidism (they are related) on July 25. I've been taking 25,000 IU of chalecalciferol (vit D3) per week since then and in a few weeks will be checked again to see if my parathyroid is responding, if not I will have to be evaluated for adenoma. But in the meantime, taking the vit D supps and have not noticed any difference either way.

My rosacea had the worst flare-up of my life after taking the second vit D supplement and I took the third one during that flare-up. Since then the flare-up naturally subsided and I am back to my baseline now (still red). I don't think vit D is making a difference either way in the short term (it's only been a few weeks and my level was so low the lab couldn't detect any at all).

I also have very low cholesterol which I think may be associated with the vit D deficiency. The whole system (parathyroid, vit D, cholesterol, and sunlight) is messed up. I think it's too early to tell if any of these things play a role in the rosacea one way or another.