Do you need vitamin K2 with vitamin D3?
Probably not. The idea that vitamin K2 steers vitamin D-driven calcium into bones rather than arteries is plausible, but human trial evidence is limited and inconsistent, and no health body recommends K2 with D3 routinely. If you take warfarin, do not add K2 without your doctor. In South Africa, D3 and K2 combinations cost about the same as plain D3.
- The NIH says it is unclear whether vitamin K supplements reduce osteoporosis risk, and makes no clinical recommendation for K2 with D.
- One trial of MK-7 at 180 µg a day for three years improved bone strength; most South African D3 and K2 products supply 45 µg.
- As of October 2026, D3 and K2 combinations cost R2.16 to R3.98 a day against R2.67 for plain Dis-Chem Gold D3.
- Warfarin works by opposing vitamin K, so K2 products need medical advice for anyone on it.
Why are D3 and K2 sold together?
Vitamin D raises calcium absorption. Vitamin K-dependent proteins help direct calcium into bone. The theory is that more D without enough K2 could leave calcium in soft tissue. The theory is reasonable, but it is not established in people.
What does the evidence say?
According to the NIH vitamin K fact sheet:
- Bone: one trial of MK-7 at 180 µg a day for three years improved bone strength and reduced vertebral height loss in postmenopausal women. In another trial giving vitamin K with calcium and vitamin D3, bone density did not change. Overall it remains unclear whether vitamin K supplements lower osteoporosis risk.
- Arteries: observational data link dietary menaquinones (K2) with less coronary calcification, but a trial using phylloquinone (K1) with calcium and vitamin D found no significant overall difference.
- Role of different forms: the NIH says the role of each vitamin K form is unclear and makes no clinical recommendation.
Because trials combine nutrients, effects cannot be assigned to K2 itself.
What do South African products contain?
| Product | D3 | K2 per dose | Price per day (October 2026) |
|---|---|---|---|
| New Leaf D3 and K2 | 1 000 IU | MK-7, amount not stated | R2.16 |
| Now Foods D3 and K2 | 1 000 IU | MK-4, 45 µg | R2.31 on special (R3.08 regular) |
| BEET Goodness D3 and K2 | 1 000 IU | MK-7, 45 µg | R2.50 |
| Neogenesis Pure D3 plus K2 | 1 000 IU | MK-7, 100 µg | R3.98 |
| Viridian D3 and K2 | 1 000 IU | MK-7, 45 µg | R8.21 |
| Dis-Chem Gold Vitamin D3 (no K2) | 1 000 IU | none | R2.67 |
Most of these supply 45 µg, a quarter of the dose used in the 180 µg bone trial, so you cannot assume trial benefits transfer. Even so, three of the five K2 versions cost less per day than plain Dis-Chem Gold D3 (R2.67), which makes the choice about preference, not budget. Full comparison: the best vitamin D3 in South Africa.
Who should not take K2?
Warfarin and similar anticoagulants work by opposing vitamin K. Sudden changes in vitamin K intake can alter their effect, so people on warfarin must keep intake consistent and speak to their doctor or anticoagulation clinic before starting or stopping any K2 product. This is the most important safety point. K2 has no established upper intake level because toxicity is low, but that does not remove the warfarin interaction.
What should you do?
- Decide whether you need vitamin D at all. Most healthy adults need the recommended 600 to 800 IU, and the Endocrine Society does not recommend extra for healthy adults under 75 (how much vitamin D to take).
- If you want a D3 product, choose on price, dose clarity and whether you are comfortable with K2.
- If you are on warfarin, choose plain D3 and talk to your clinician.
- If you have osteoporosis, ask your doctor about evidence-based bone treatment rather than relying on a supplement.
Neither D3 nor K2 is banned in sport, but drug-tested athletes should still treat all supplements with caution (strict liability applies). Our October 2026 sources found no third-party certification for these products. See also do South Africans need vitamin D in summer?.
Products mentioned, with dated prices
| Product | Size | Price | Servings | R per serving | Sweeteners |
|---|---|---|---|---|---|
| BEET Goodness Vitamin D3 and K2 60 tablets | 60 tablets | R150Faithful to Nature, Oct 2026 | 60 | R2.50 | not stated |
| Now Foods Vitamin D3 and K2 120 vegicaps | 120 capsules | R276.75-R369 (special vs regular)Faithful to Nature, Oct 2026 | 120 | R2.31 | not stated |
| Neogenesis Pure D3 + K2 (1000 IU + 100 mcg) 60 capsules | 60 capsules | R239Faithful to Nature, Oct 2026 | 60 | R3.98 | not stated |
| Dis-Chem Gold Vitamin D3 1000 IU 60 tablets | 60 tablets | R160Dis-Chem Living Fit, Oct 2026 | 60 | R2.67 | not stated |
Compare the options
- Best Magnesium Supplement in South Africa 2026: 7 Products Compared
- Best Omega-3 Fish Oil in South Africa 2026: 9 Products Compared
- Best Multivitamin in South Africa 2026: 7 Products Compared
Related questions
- What is the best vitamin D3 supplement in South Africa?
- How much vitamin D should I take in South Africa?
- Do South Africans need vitamin D supplements in summer?
- Do women need vitamin D and calcium for bone health?
- Can you overdose on vitamins and minerals?
Sources
- NIH Office of Dietary Supplements: Vitamin K, health professional fact sheet
- NIH Office of Dietary Supplements: Vitamin D, health professional fact sheet
- Endocrine Society 2024 guideline press release: healthy adults should take the recommended daily allowance of vitamin D
- SAIDS (South African Institute for Drug-Free Sport) FAQ: supplements, strict liability, medication check
Educational information only, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease.
Cite this page: Healthnews24, “Do you need vitamin K2 with vitamin D3?”, updated 27 October 2026, https://www.healthnews24.co.za/answers/vitamin-d3-with-k2-do-you-need-it/. Plain-text version: /answers/vitamin-d3-with-k2-do-you-need-it.md