At a glance
- D3 increases how much calcium you absorb. K2 activates the proteins that direct where it goes.
- That division of labour is the reason the two are commonly taken together.
- MK-7 is the longer-lasting form of K2 and the one used in most modern research.
- Vitamin K interacts with warfarin and other anticoagulants. Speak to your doctor first.
- 5000 IU is above the general adult upper intake level. Worth a conversation with your doctor, ideally with a blood test.
Vitamin D is one of the more common nutrient gaps in adults, and most people who supplement take D3 on its own. The argument for adding K2 is not about taking more of something — it is about what happens to the calcium once D3 has done its job.
What each one does
Vitamin D3 (cholecalciferol) is the form your body produces from sunlight, and the more bioavailable of the two dietary forms. Its main role is increasing calcium absorption in the intestine — opening the door for calcium to enter the bloodstream.
Vitamin K2, specifically the MK-7 form, activates two calcium-regulating proteins. Osteocalcin binds calcium into the bone matrix. Matrix Gla protein is involved in regulating where calcium is deposited in soft tissue.
So D3 governs how much calcium arrives. K2 is involved in where it ends up. That is the whole argument for the pairing, and it is a mechanistic one rather than a claim about outcomes.
Why MK-7 specifically
Vitamin K2 comes in several forms. MK-4 is cleared from the bloodstream within hours. MK-7 has a considerably longer half-life, which is why it is the form used in most modern research and why a once-daily dose is practical.
If a label says "vitamin K2" without specifying the form, that is worth noticing.
What the research covers
The biochemistry here is well established. Osteocalcin and matrix Gla protein are both vitamin K–dependent, meaning they require vitamin K to become active. Without adequate K status, both remain partly uncarboxylated — the inactive form.
Much of the clinical research on K2 has been conducted in specific patient populations with diagnosed conditions, examining disease progression. That research is real and it is why the mechanism is taken seriously. It does not translate into claims about what a supplement does for a healthy person, and we are not going to present it as though it does.
What can be said: vitamin K is required for these proteins to function, and adequate status of both nutrients supports normal bone health.
A note on dose
Our formula provides 5000 IU of D3. The National Academies set the tolerable upper intake level for adults at 4,000 IU per day.
Higher doses are commonly used and are widely available, but 5000 IU is above that threshold, and we would rather say so than leave it in the small print. If you are supplementing at this level, it is worth a conversation with your doctor — ideally alongside a blood test, since vitamin D status is one of the few nutrient levels that is straightforward to measure.
Who tends to consider it
- People with limited sun exposure, particularly through winter months
- Anyone with a diagnosed vitamin D deficiency, on medical advice
- Adults already supplementing D3 alone who want the K2 alongside it
- Older adults focused on maintaining normal bone health
Who should be cautious
Anyone taking anticoagulant medication. Vitamin K directly interacts with warfarin and similar drugs. This is not a minor interaction — speak to your doctor before starting.
Anyone with kidney disease or a calcium-related condition. Both nutrients affect calcium handling.
Pregnant or nursing women, without clearing it with a healthcare provider.
Anyone already taking a multivitamin. Check the combined vitamin D total; it is easy to double up without noticing.
Ours provides 5000 IU D3 and 100mcg K2 as MK-7, in a virgin coconut oil base, 300 softgels.
See Cures For Life Vitamin D3 + K2
Frequently asked questions
Why take D3 and K2 together rather than D3 alone?
D3 increases calcium absorption. K2 activates the proteins involved in directing calcium into bone. The two work on different parts of the same process, which is the rationale for combining them.
What is MK-7 and why does it matter?
MK-7 is a form of vitamin K2 with a longer half-life than MK-4, staying active in the bloodstream considerably longer. It is the form used in most modern research and suits once-daily dosing.
Can I take this with blood thinners?
Not without medical advice. Vitamin K interacts directly with warfarin and similar anticoagulants. Speak to your doctor before starting.
Is 5000 IU too much vitamin D?
It is above the 4,000 IU upper intake level set for adults. It is a common supplement dose and widely available, but worth discussing with your doctor, ideally with a blood test to establish your current level.
Should I take it with food?
Yes. Both vitamins are fat-soluble, so a meal containing some fat supports absorption. Ours uses a coconut oil base for the same reason.
Can I get enough from sunlight and diet?
Some people can. It depends on latitude, season, skin tone and how much time you spend outdoors. A blood test is the only way to know where you stand.
References
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press.
- Schurgers LJ, Vermeer C. Determination of phylloquinone and menaquinones in food: effect of food matrix on circulating vitamin K concentrations. Haemostasis. 2000;30(6):298-307.
- Sato T, Schurgers LJ, Uenishi K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J. 2012;11:93.
- Booth SL. Roles for vitamin K beyond coagulation. Annu Rev Nutr. 2009;29:89-110.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Consult your healthcare provider before beginning any new supplement, especially if you take blood-thinning medication.
