Age also has a big effect on serum levels. When you are mid-40s+, you cannot absorb D3 as well, and it takes a significantly higher dose to get your serum levels up. This is why testing is important.
It is also important to take K2 when you are taking higher doses of D3. Even if you have a higher than normal serum level, K2 mediates the metabolism of D3, and prevents issues. I've seen numerous examples of this, verified by CAC tests which consistently score 0 in people taking 10,000 IU of D3 with 100mg K2 for extended periods of time.
It is also important to take K2 when you are taking higher doses of D3. Even if you have a higher than normal serum level, K2 mediates the metabolism of D3, and prevents issues. I've seen numerous examples of this, verified by CAC tests which consistently score 0 in people taking 10,000 IU of D3 with 100mg K2 for extended periods of time.