Mercola has a good article (link below) but he wants your email before you can read it. So: Story at-a-glance If you take supplemental vitamin D3, you also need to be mindful of taking extra vitamin K2 and magnesium It’s important to increase your vitamin K2 intake when taking high-dose supplemental vitamin D to avoid complications associated with excessive arterial calcification You need 146% more vitamin D to achieve a blood level of 40 ng/ml (100 nmol/L) if you do not take supplemental magnesium, compared to taking your vitamin D with at least 400 mg of magnesium per day Vitamin D improves magnesium absorption, but taking large doses of vitamin D can deplete magnesium, as magnesium is required in the conversion of vitamin D into its active form Combined intake of both supplemental magnesium and vitamin K2 has a greater effect on vitamin D levels than either individually. You need 244% more oral vitamin D if you’re not concomitantly taking magnesium and vitamin K2 https://articles.mercola.com/sites/articles/archive/2022/01/11/vitamin-d3-k2-and-magnesium.aspx