Good article. My ng/ml 25(OH)D blood level a few years ago was 21 when I had breast cancer and subsequent mastectomy, even though I have lived in Greece for decades. I had avoided midday sun due to having a stage 1 melanoma years ago. I started supplementing vit D and my numbers only inched up. It was only when I consistently took daily 5000 IU plus K2 that I've reached 59 ng/ml 25(OH)D blood levels. Another commenter asked about your 10,000 IUs - will you lower when you reach levels you want, or keep up those amounts? I see it's been a couple of years so presumably you've retested.