Vitamins D3 and K2 work together to aid in calcium absorption and regulation. Vitamin D3 helps the body absorb calcium from the diet. Without adequate vitamin D3, calcium can’t be efficiently absorbed, no matter how much is consumed.

Vitamin K2, on the other hand, helps direct the calcium to the right places—mainly the bones and teeth. It activates certain proteins like osteocalcin, which help bind calcium to the bone matrix.

If there are high levels of calcium in the bloodstream and not enough K2 to direct it to the bones, it can lead to calcium buildup in blood vessels, contributing to arterial calcification and an increased risk of heart disease.

Vitamin D3 and K2 are essential for bone health. Vitamin D3 boosts calcium absorption, and vitamin K2 ensures it is effectively used to build and strengthen bones. Without K2, calcium may end up in the bloodstream or soft tissues like arteries rather than in the bones, leading to weaker bones and a higher risk of osteoporosis and plaque in the blood vessels.

Some other healthy effects of vitamin D3 include supporting the innate and adaptive immune systems. Low D3 levels can be associated with increased autoimmunity and susceptibility to infections.

Taking calcium without sufficient vitamin D3 and K2 can lead to inefficient calcium use, weaker bones, and potential calcification of soft tissues, increasing the risk of cardiovascular disease and other complications. Vitamin D also influences the expression of more than 2,000 genes, including those responsible for the regulation of cellular proliferation, cell differentiation, apoptosis and angiogenesis. The immune-modulating effects of vitamin D are profound, as evidenced by the many conditions associated with vitamin D deficiency.

Knowing vitamin D3 levels is important because vitamin D deficiency has been linked to an increased risk of many common and serious diseases, including some cancers, diabetes, cardiovascular disease and osteoporosis. Deficiency is also prevalent in infants that are solely breastfed and don’t receive vitamin D supplementation. Adults of all ages with darker skin (increased skin melanin) or those that always wear sun protection or limit outdoor activities, such as homebound elderly individuals, are also prone to vitamin D deficits.

Sunlight exposure is a natural source of vitamin D and has been shown to prevent many chronic diseases. Low levels of vitamin D are also linked to seasonal depression, particularly during the winter months with less sunlight exposure. Vitamin D can also be obtained through diet and supplementation, although few food sources (fatty fish, fish liver oil and eggs) contain it naturally. Fortified foods may contain synthetic forms of vitamin D, which are less potent and have a shorter lifespan in the body.

To determine if the right amount of vitamin D3 is being taken, MosaicDX’s Vitamin D Test is a dried blood spot analysis that quantitates 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 metabolites. The metabolite 25-hydroxyvitamin D is the major circulating form of vitamin D in the body and the best indicator of true vitamin status.

This simple blood spot test (a finger prick done at home to determine vitamin D3 levels) can guide individuals as to how much D3/K2 is needed. No blood draw is necessary if a vitamin D level check cannot be done with a healthcare provider.