Most premium D3 bottles in South Africa now ship with vitamin K2 included. The marketing is that K2 directs the calcium D3 mobilises to bones, not arteries. The reality is more nuanced — and depends on what you're solving for.
What D3 does
Vitamin D3 increases intestinal calcium absorption. At a 1,000–2,000 IU daily dose it raises serum 25(OH)D into the 75–125 nmol/L range most clinicians target, which supports immune function, mood, and bone density.
What K2 adds
K2 (specifically MK-7) activates two proteins — osteocalcin (which moves calcium into bone) and matrix Gla protein (which keeps calcium out of arterial walls). The headline trial (Knapen et al., 2013) showed 180 mcg MK-7 over 3 years improved bone mineral density and arterial stiffness markers in postmenopausal women.
So is D3+K2 worth the price?
If you're over 50, postmenopausal, or have known low bone density — yes, the combination is supported by the evidence. If you're a healthy 30-year-old supplementing D3 for general immunity, the K2 upside is small and standalone D3 is fine.
Dose notes
- D3 — 1,000–2,000 IU daily for most adults. Higher (4,000 IU) under clinician guidance if labs show deficiency.
- K2 — 90–180 mcg MK-7 daily. MK-7 (long half-life) preferred over MK-4 for daily dosing.
- Take with a meal containing fat — both are fat-soluble.