Vitamin D With or Without K2: Do You Need Both?
Yes, you can take vitamin D without K2: plain D3 at 1,000 to 2,000 IU a day is enough for most people. No trial has tested D3 with K2 against D3 alone for broken bones or heart problems, so K2 is optional. If you take warfarin, skip K2 unless your doctor says yes.
By Erin Rose Updated October 20, 2026 How we score
Which should you buy?
Most people: plain vitamin D3
You don’t need K2 for vitamin D to work. A plain 2,000 IU softgel covers most adults; ours is NatureWise, on NSF/ANSI 173.
NatureWise D3 2000 IU
$0.04 a day · 2,000 IU · NSF/ANSI 173
Doctor says 5,000 IU and you want K2: one softgel
Nature Made D3 + K2 puts 5,000 IU of D3 and 100 mcg of K2 (as MK-7) in one softgel, and it is on USP Verified. 5,000 IU is above the 4,000 IU adult upper limit, so take it on a doctor’s advice.
Nature Made D3 + K2
$0.42 a day · 5,000 IU + 100 mcg K2 · USP Verified
Same dose for less: not on a testing list
Sports Research D3 + K2 has the same 5,000 IU and 100 mcg of K2 (MK-7) a softgel. It is not on a testing list we check, and 5,000 IU is above the adult limit.
Sports Research D3 + K2 (30 softgels)
$0.57 a day · 5,000 IU + 100 mcg K2
Want drops?
Thorne Vitamin D + K2 is a liquid: 2 drops give 1,000 IU of D3 and 200 mcg of K2, and it is on NSF/ANSI 173. Its K2 is the MK-4 form; see MK-7 or MK-4 below.
Thorne Vitamin D + K2 Liquid
$0.11 a day · 1,000 IU + 200 mcg K2 a serving · NSF/ANSI 173
Want K2 at 2,000 IU?
We read 6 labels of one-pill D3 + K2 products, and all 6 have 5,000 IU of D3. To get K2 with 2,000 IU, take plain D3 and a separate K2. See the best vitamin K2.
What K2 trials found
K2 helps your body use calcium. Here is what trials found when people took it, most often by itself.
| What they measured | What trials found |
|---|---|
| Bone density, K2 alone | 180 mcg of MK-7 a day for 3 years slowed bone loss in the spine and the top of the thigh bone in 244 women past menopause (Knapen 2013). |
| Bone density, K with vitamin D | Raised bone density a little in 8 trials (Kuang 2020). |
| Broken bones | In the best-run trials, vitamin K did not clearly lower fractures (Mott 2019). |
| Heart artery calcium scores | Two 2026 trials in people who already had calcium in their heart arteries found the scan score rose more slowly on K2 (Vossen 2026, Hasific 2026). These are scan scores, not heart attacks. |
| Heart valve calcium | K2 with vitamin D for 2 years did not slow calcium in the aortic valve (Diederichsen 2022). |
Does vitamin D put calcium in your arteries without K2?
That idea comes from a theory, not a trial. We found no trial showing that a normal dose of D3 alone hardens arteries. In the largest vitamin D trial, 2,000 IU a day for about five years caused no extra cases of high blood calcium (Manson 2019).
MK-7 or MK-4?
If you buy K2, MK-7 is the usual pick. In one study, MK-7 raised K2 in the blood at supplement doses, while MK-4 at small doses did not (Sato 2012). More in MK-7 vs MK-4.
If you take warfarin
K2 can lower the effect of warfarin, a blood thinner. In one study, MK-7 at 50 mcg a day or more was enough to matter (Schurgers 2007). Take plain D3, or ask your doctor before adding any K2.
Questions people ask
How much K2 should you take with vitamin D?
There is no set daily amount for K2. The 3-year bone trial used 180 mcg of MK-7 a day (Knapen 2013), and most D3 + K2 softgels have 100 mcg. More on dose: vitamin K2 dosage.
Can you take K2 without vitamin D?
Yes. K2 is sold on its own, and the bone and heart trials above mostly gave K2 by itself. See the best vitamin K2.
Sources
- Knapen MH, et al. “Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women.” Osteoporos Int. 2013. PubMed 23525894
- Kuang X, et al. “The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials.” Food Funct. 2020. PubMed 32219282
- Mott A, et al. “Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials.” Osteoporos Int. 2019. PubMed 31076817
- Vossen LM, et al. “Two years of menaquinone-7 supplementation and coronary artery calcification: a randomized clinical trial.” JAMA Cardiol. 2026. PubMed 42268593
- Hasific S, et al. “Vitamin K2 and D3 supplementation in patients with severe coronary artery calcification: the DANCODE trial.” Circulation. 2026. PubMed 42661461
- Diederichsen ACP, et al. “Vitamin K2 and D in patients with aortic valve calcification: a randomized double-blinded clinical trial.” Circulation. 2022. PubMed 35465686
- Manson JE, et al. “Vitamin D supplements and prevention of cancer and cardiovascular disease.” N Engl J Med. 2019. PubMed 30415629
- Sato T, et al. “Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women.” Nutr J. 2012. PubMed 23140417
- Schurgers LJ, et al. “Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7.” Blood. 2007. PubMed 17158229
- Labels: NIH Dietary Supplement Label Database (Thorne Vitamin D + K2, label 336339; Nature Made D3 + K2, label 285746). Testing lists: USP Verified and NSF/ANSI 173.