Some are saying if we take D3 we must take K2, but many people don’t need K2 if they can produce K2 in the gut and/or eat enough K2 producing foods.
Also, in sunny climates, those who spend enough time outside have high vitamin D blood levels, yet they’re not warned to also take K2. People can get 10,000 iu or more every half hour in strong sun with enough skin showing, and they’re not warned they must take K2.
The microbes in your gut have the ability to make vitamin K2, but fermented foods and fatty foods are also rich in vitamin K2.