Vitamin D3 + K2

Most people are deficient. In serious illness, the stakes are higher.

What it is

Vitamin D3 (cholecalciferol) is the active supplemental form of vitamin D, a hormone precursor involved in hundreds of physiological processes. K2 (MK-7 form) is added to direct calcium to bones rather than arteries.

Why it matters

Vitamin D receptors are present in nearly every cell type. Deficiency is associated with immune dysfunction, poor mood, muscle weakness, and worse outcomes across a range of diseases. In oncology, low D3 status correlates with worse prognosis in several cancer types. Dark Slovak winters make deficiency almost guaranteed without supplementation.

The evidence

Serum 25(OH)D levels below 30 ng/mL are considered deficient. Most supplementation studies use 2,000–5,000 IU daily to reach optimal levels (50–80 ng/mL). K2 co-supplementation prevents hypercalcemia risk at higher D3 doses.

This information is for educational purposes and does not constitute medical advice. Always discuss supplement use with your care team, particularly if you are undergoing active cancer treatment.

Dosing

3,000–5,000 IU D3 daily with K2 100–200mcg (MK-7 form). Take with a fatty meal.

Cautions

Get your 25(OH)D levels tested before starting. Toxicity is possible at very high doses over time. Avoid if you have certain granulomatous diseases (sarcoidosis, etc.).