I read that if you take more than 4,000 IU D3 daily, you need to also take K2 so that calcium is used correctly and does build up on arteries. The MK-7 type of D3 is recommended.
We take 5,000 in winter and 2,000 in summer with lots of sunshine. However, we’ve also read the skin’s ability to produce D3 decreases in seniors and as people age.
I had to stop taking Calcium supplements many years ago because they found out I have a hyper para-thyroid that produces more calcium than my body needs. My calcium levels are always high in my bloodwork. Other than taking out those glands if it gets worse, there's nothing they can do about it.