I stopped all my supplements after I was diagnosed with cancer.
I am so sorry. My prayers are with you.
I take about 7,500 IU daily to maintain a level around 50-60 ng/ml. I used to stop in the summer because I’m outside a lot then, but my level would drop, so now I just take it year round. The older you are, the less able your skin becomes to convert sunlight to D3.
As for the K2, there’s a fairly expensive brand out there, BioTech’s D3 Plus, that has several cofactors believed to work in concert with D3. It has vit K, magnesium, zinc, and boron included in the mix. Because it’s expensive, I mix in a straight vit D3 of a good, but cheaper, brand along with the BioTech product. If cost isn’t an issue, I’d just go with BioTech’s product.
A good source of information is this site: http://www.vitamindcouncil.org
On that page you can sign up for a regular email newsletter. After you’ve browsed several issues, you’ll be convinced to consider D3 supplementation or getting more sun. They cover many of the recent studies as they come out and it’s interesting how many medical issues correlate with D3 deficiency. And it’s not a site that just publishes the pros. If studies are inconclusive, or show a disadvantage, or no effect, they cover those too.
One of the main reasons so many studies are now being done is that the government doubled the Tolerable Upper Limit to 4,000 IU just a few years ago. That enabled scientists to ethically administer those higher doses in studies, and that’s why they’re finding more results. The lower levels wouldn’t get D3 levels high enough to be effective.