Vitamin D3 and K2: Benefits, How Much to Take and When

Vitamin D3 and K2 are often sold together, and for a good reason: they work on the same job. Vitamin D3 helps you absorb calcium, and vitamin K2 activates the proteins that decide where that calcium goes. This guide explains the benefits of taking vitamin D3 with K2, how much to take, when to take them, and who should check with a clinician first.

It is educational, not medical advice.

Key Takeaways

• They are a team. Vitamin D3 raises calcium absorption and tells the body to make calcium-handling proteins; vitamin K2 switches those proteins on.
• Vitamin D3: the adult RDA is 600 IU a day (800 IU over 70), and the upper limit is 4,000 IU a day from all sources unless your clinician advises more.
• Vitamin K2: adequate intake for all vitamin K is 90 mcg a day for women and 120 mcg for men. A 3-year trial used 180 mcg of K2 as MK-7 a day.
• Take them with a meal that has some fat, since both are fat soluble. Morning or midday suits most people; consistency matters more than the hour.
• On a blood thinner such as warfarin? Do not start K2 without your clinician, because vitamin K changes how warfarin works.

What Vitamin D3 and K2 Each Do

	Vitamin D3	Vitamin K2
Main job	Helps the gut absorb calcium and phosphorus	Activates proteins that bind calcium
Key proteins	Signals the body to make osteocalcin (in bone) and matrix Gla protein (in soft tissue)	Switches on (carboxylates) osteocalcin and matrix Gla protein so they can bind calcium
Main forms	D3 (cholecalciferol) and D2 (ergocalciferol)	MK-7 and MK-4 (menaquinones)
Food sources	Fatty fish, egg yolks, fortified foods, plus your skin makes it from sunlight	Natto (fermented soybeans), some cheeses, egg yolks, chicken

Vitamin D3 (cholecalciferol) is the form your skin makes from sunlight. Both D3 and D2 raise blood vitamin D, but D3 may raise it higher and keep it up longer (NIH Office of Dietary Supplements: Vitamin D). Most D3 in supplements comes from lanolin, the wax in sheep’s wool; vegan D3 comes from lichen. More on the basics is on our vitamin D3 ingredient page and in our vitamin D3 supplement guide.

Other nutrients matter for vitamin D too: magnesium is needed to activate it, and boron may help it last longer in the blood. Our Vitamin D Cofactor Capsules combine magnesium, zinc and boron (join the waitlist), and our boron guide covers the evidence.

Vitamin K2 is a family of forms called menaquinones. The two you will see on labels are MK-7, which comes from fermentation and stays in the blood for days, and MK-4, which clears within hours and is usually used at higher amounts. Vitamin K1, from leafy greens, is mostly used by the liver for normal blood clotting. For their chemistry, label forms and the human studies, see our vitamin K2 (MK-4 and MK-7) reference page.

If you are unsure how vitamin D3 differs from D2, our vitamin D vs D3 guide compares the two forms.

What Is Vitamin D3 and K2 Good For?

In short: vitamin D3 helps your body absorb calcium and supports muscles, nerves and the immune system, and vitamin K2 activates the proteins that put calcium to work in bone. Here is what each one does, in the words of the NIH:

• Bones: vitamin D helps your body absorb calcium, one of the main building blocks for strong bones (NIH Office of Dietary Supplements: Vitamin D).
• Muscles and nerves: your muscles need vitamin D to move, and your nerves need it to carry messages between your brain and your body (NIH Office of Dietary Supplements: Vitamin D).
• Immune system: vitamin D supports normal immune function (NIH Office of Dietary Supplements: Vitamin D).
• Calcium-binding proteins: vitamin K activates osteocalcin in bone and matrix Gla protein in soft tissue, and it is needed for normal blood clotting (NIH Office of Dietary Supplements: Vitamin K).

That is why the two are paired: D3 brings calcium in, and K2 helps direct it. The research on the pair is below.

Why Take Vitamin D With K2?

Vitamin D increases the amount of calcium you absorb and prompts the body to make vitamin K-dependent proteins. Those proteins only work once vitamin K has activated them. When vitamin K runs low, more of them stay inactive (van Ballegooijen et al., 2017). Taking the two together covers both steps: D3 brings calcium in and K2 helps put it to work.

• Osteocalcin is made by bone-building cells. Once activated by vitamin K, it binds calcium into the bone matrix.
• Matrix Gla protein is made in soft tissues such as blood vessel walls. Once activated, it helps regulate where calcium is deposited.

Researchers who reviewed the evidence on vitamins D and K together describe them as working in synergy, and note that most human trials so far have tested them in postmenopausal women and focused on bone (van Ballegooijen et al., 2017).

Vitamin D3 and K2 Benefits: What the Research Shows

• Bone density with K2. In a 3-year trial of 244 healthy postmenopausal women, 180 mcg of MK-7 a day improved vitamin K status and slowed the usual age-related decline in bone mineral density at the spine and hip, and improved measures of bone strength compared with placebo (Knapen et al., 2013).
• Calcium absorption with D3. Vitamin D helps your body absorb calcium, one of the main building blocks of bone (NIH Office of Dietary Supplements: Vitamin D).
• Protein activation. Vitamin D raises production of osteocalcin and matrix Gla protein, and vitamin K is what activates them, which is the reason the two are paired (van Ballegooijen et al., 2017).

Benefits build slowly. Blood vitamin D takes weeks of steady intake to reach a new level, and the bone results above were measured over years, not weeks.

For vitamin D from food, see foods high in vitamin D; for vegan sources of D3, see vegan vitamin D3.

Vitamin D3 and K2 for Women and Men

Vitamin D needs are the same for women and men: 600 IU (15 mcg) a day for adults up to 70, 800 IU (20 mcg) after that, and 600 IU during pregnancy and breastfeeding (NIH Office of Dietary Supplements: Vitamin D). Vitamin K needs differ a little, with an adequate intake of 90 mcg a day for women and 120 mcg for men (NIH Office of Dietary Supplements: Vitamin K).

• Women: the longest K2 trial was in women. In 244 healthy postmenopausal women, 180 mcg of MK-7 a day for 3 years slowed the usual age-related decline in bone mineral density at the spine and hip (Knapen et al., 2013). Pregnant or breastfeeding? Use the amounts your clinician recommends.
• Men: the same calcium and bone roles apply. For what K2 research has measured in men, see the men section of vitamin K2: MK-4 vs MK-7.

Women can find the amounts for each life stage in our guide to vitamin D for women. Men can find D3 and K2 amounts in our guide to vitamin D for men.

How Much Vitamin D3 and K2 Should You Take Daily?

	Vitamin D3	Vitamin K2
Official daily target for adults	600 IU (15 mcg) to age 70; 800 IU (20 mcg) over 70	Adequate intake for all vitamin K: 90 mcg women, 120 mcg men
Upper limit	4,000 IU (100 mcg) a day from food and supplements combined	None set; no harm reported from food or supplements in healthy people
Amounts in studies and on labels	Label amounts vary; keep your total from all sources within the upper limit	180 mcg MK-7 a day in the 3-year trial; label amounts vary

Sources: NIH Office of Dietary Supplements: Vitamin D and NIH Office of Dietary Supplements: Vitamin K.

• Follow your product label and stay within 4,000 IU of vitamin D a day unless your clinician recommends more after a blood test.
• IU and mcg: 1 mcg of vitamin D equals 40 IU, so 1,000 IU is 25 mcg and 2,000 IU is 50 mcg.
• Test if unsure. A 25(OH)D blood test shows your vitamin D status; recheck about 3 months after changing your dose.

Calcium is the third partner in this team; see vitamin D and calcium.

When to Take Vitamin D3 and K2

• With food that has some fat. Both are fat soluble, and vitamin D is best absorbed with a meal or snack that includes fat (NIH Office of Dietary Supplements: Vitamin D). Drops made in oil carry some fat of their own; taking them with a meal is still the simplest habit.
• Morning or midday fits most routines. There is no strong evidence that one hour is better than another, so pick a time you will keep.
• Every day, at the same time. MK-7 stays in the blood for about two days after a dose, while MK-4 clears within hours, so daily use keeps levels steady (Sato et al., 2012).
• With other supplements: taking vitamin D and magnesium at the same meal is fine for most people.

If you are choosing between a liquid and a capsule, our guide to vitamin D drops vs pills compares what studies found for each format. Our guide to the best time to take vitamin D covers the studies on meals and timing. If you also take fish oil, see vitamin D3, K2 and omega-3 together.

MK-7 or MK-4?

In a study of healthy women, a single 420 mcg dose of MK-7 peaked in the blood at 6 hours and was still measurable at 48 hours (Sato et al., 2012). MK-4 leaves the blood within hours, so it is used at larger amounts, and it is also the form the body makes from vitamin K1. Some formulas combine both forms.

For a closer look at the two forms and how much of each is used, see vitamin K2: MK-4 vs MK-7.

From Synchronicity: our Vitamin D3 + K2 Drops pair vegan vitamin D3 from lichen with vitamin K2 as MK-4 and MK-7 in a clean MCT oil base, one drop a day. Each bottle holds about 180 drops, about 6 months at one drop a day.

Each drop gives vitamin D3 50 mcg (2,000 IU), within the 4,000 IU adult upper limit, and vitamin K 300 mcg as MK-7 200 mcg and MK-4 100 mcg, in MCT oil from coconut. They are vegan, gluten free, non-GMO, soy free and dairy free.

To get K2 from food, our guide to vitamin K2 foods lists the best MK-4 and MK-7 sources with NIH values.

Who Should Check With a Clinician First

Vitamin K2 itself is very well tolerated; our guide to vitamin K2 side effects covers what trials found. These are the situations to raise with your clinician:

• Blood thinners: if you take warfarin, keep your vitamin K intake steady and do not start K2 without your clinician, because changes in vitamin K can make warfarin work more or less strongly (NIH Office of Dietary Supplements: Vitamin K).
• Medicines that interact with vitamin D: steroids such as prednisone, orlistat, some statins and thiazide diuretics (NIH Office of Dietary Supplements: Vitamin D).
• High calcium or kidney problems: ask your clinician before taking vitamin D.
• Too much vitamin D over time can raise blood calcium, with symptoms such as nausea, weakness, confusion and thirst. Stay within the upper limit unless you are being monitored.
• Pregnancy and breastfeeding: use the amounts your clinician recommends.

Related reading: vitamin D3 benefits, dosage and smart use, how to read a supplement label and what third-party tested means.

Sources

• National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Consumers. NIH ODS
• van Ballegooijen AJ et al. The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review. Int J Endocrinol, 2017. DOI
• Knapen MH et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int, 2013. DOI
• National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. NIH ODS
• Sato T et al. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J, 2012. DOI

Frequently Asked Questions

Should you take vitamin D with K2?

Many people do, because vitamin D raises calcium absorption and makes calcium-binding proteins, and vitamin K2 activates those proteins. If you take a blood thinner such as warfarin, talk with your clinician first.

What are the benefits of vitamin D3 and K2 together?

D3 helps you absorb calcium, and K2 activates osteocalcin in bone and matrix Gla protein in soft tissue. In a 3-year trial, 180 mcg of MK-7 a day slowed the age-related decline in bone density in postmenopausal women.

How much vitamin D3 and K2 should I take daily?

The adult RDA for vitamin D is 600 IU (800 IU over 70), with an upper limit of 4,000 IU. Adequate intake for vitamin K is 90 mcg for women and 120 mcg for men, and the 3-year trial used 180 mcg of MK-7. Follow your product label.

When is the best time to take vitamin D3 and K2?

With a meal or snack that contains some fat, at the same time each day. Morning or midday works well for most people.

Is vitamin K2 a blood thinner?

No. Vitamin K supports normal blood clotting, which is why it can change how warfarin works. If you take warfarin, keep vitamin K intake steady and check with your clinician before starting K2.

What is the difference between MK-4 and MK-7?

Both are forms of vitamin K2. MK-7 stays in the blood for about two days after a dose, while MK-4 clears within hours and is usually used at larger amounts.

Is vitamin D3 vegan?

Most D3 comes from lanolin in sheep’s wool. Vegan D3 is made from lichen, so check the label for the source.

What is vitamin D3 and K2 good for?

Vitamin D3 helps you absorb calcium and supports muscles, nerves and immune function. Vitamin K2 activates osteocalcin and matrix Gla protein, which bind calcium, and vitamin K is needed for normal blood clotting.

Is vitamin D3 and K2 good for women?

Yes, it suits women well. The longest K2 trial, 3 years of 180 mcg MK-7 a day, was in postmenopausal women and slowed the usual decline in bone density. Women need 600 IU of vitamin D a day (800 IU over 70) and 90 mcg of vitamin K.

Can I take vitamin D3 and K2 every day?

Yes, daily use is how they were studied. Keep your total vitamin D within 4,000 IU a day from all sources unless your clinician advises more, and talk with your clinician first if you take warfarin.

How long does it take for vitamin D3 and K2 to work?

Blood vitamin D takes weeks of steady intake to settle at a new level, so a recheck about 3 months after starting is common. The bone results with K2 were measured over years.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.