Can You Take Vitamin D and Vitamin K Together?

Vitamin D and vitamin K are two nutrients your body needs for proper functioning. They are both found naturally in food and are also available as supplements. Vitamins D and K can be taken as individual supplements or through a multivitamin that contains both. Usually it's vitamins D3 and K2 that are in these combination products. 

Although vitamin D has many potential health benefits, its most established is preventing and treating osteoporosis, a disease that causes weakened and brittle bones. Vitamin K is most known for its role in blood clotting. However, researchers are learning more about additional benefits, such as strengthening bones.

The two vitamins may have a synergistic effect when it comes to building bone. For example, at least in animal models, vitamin K may be most effective in increasing bone mass when vitamin D levels are increased.

However, many traditional healthcare providers in the U.S. do not recommend supplemental vitamin K in most situations, and they only recommend taking supplemental vitamin D for some people. 

But if both vitamin D and vitamin K are supplements your healthcare provider has recommended, know that combined products containing the two vitamins are typically safe for most people—especially if taken at lower doses for limited periods. Still, it’s always best to review the benefits and risks with your provider, especially if you have underlying medical conditions.

Benefits of Vitamin D

Vitamin D’s most established role in health is in regulating minerals such as calcium. So if a person is deficient in vitamin D, their calcium levels might not be optimally regulated which means they may be at greater risk for osteoporosis. Because of this, treatment and prevention of osteoporosis is the most common reason a healthcare provider might recommend you take vitamin D.

Vitamin D can help with other areas of bone health too, including treating bone softening (osteomalacia). Evidence is not strong enough to say whether vitamin D has any significant benefit on health measurements unrelated to bone health. Still, research suggests vitamin D might be effective for the following:

• Allergic rhinitis (hay fever): Taking vitamin D may reduce symptoms of hay fever, an allergy to pollen that can cause sneezing and watery, itchy, red eyes.
• Dental decay: Children might be less likely to develop tooth decay if they take vitamin D supplements.
• Heart failure: People who take vitamin D might be less likely to develop heart failure.
• Respiratory tract infections: Children who take vitamin D might be less likely to develop these infections.

Vitamin D might also have benefits for a multitude of other conditions, including depression and cancer, but more research is needed to confirm.

Keep in mind vitamin D may not be helpful unless the levels of vitamin D in your blood are low. 

Benefits of Vitamin K

Compared to vitamin D, the benefits of taking supplemental vitamin K are not as well established. Multiple trials have shown that supplemental vitamin K may help with osteoporosis, but other trials have not replicated these results.

Currently, U.S. medical guidelines don’t recommend testing for vitamin K or using vitamin K as part of osteoporosis treatment or prevention. However, in other parts of the world, vitamin K is commonly used for osteoporosis.

Researchers are also actively exploring whether vitamin K might help prevent some kinds of heart disease and blood vessel disease, potentially by reducing damaging deposits of calcium and other minerals in blood vessels.

Under the care and guidance of a healthcare provider, vitamin K might also be used in the treatment of several bleeding-relating conditions, including excess bleeding from taking too much of the blood thinner warfarin (Coumadin).   

Benefits of Taking Vitamin D and Vitamin K Together

Potentially, taking vitamins D and K together might be more effective in preventing or treating osteoporosis than taking either one alone because they may have a synergistic effect. Researchers still need to learn more to say for sure. 

Early research suggests the supplement combination might modestly improve bone mineral density at the lumbar spine among children with beta-thalassemia, a blood disorder that reduces the production of hemoglobin. The improvements were seen after the children took 50 micrograms (mcg) of the MK-7 form of vitamin K2 per day as well as 5 mcg of vitamin D3 per day for one year. However, researchers aren't sure whether the improvement came from the combination or the vitamin K or D3 alone.

For people already taking vitamin D, adding vitamin K might be protective. Vitamin D can cause increased levels of calcium in the blood, which may lead to mineral deposits in blood vessels that can increase the risk of heart disease. Some supplement manufacturers claim taking vitamin K along with your vitamin D might decrease such risks.

How To Take a Combination of Vitamin D and Vitamin K

Vitamin D is sold as a pill, powder, or liquid, most commonly in the form of D3. It can also be prescribed as an injection for higher doses. 

Similarly, Vitamin K can be taken as a pill, powder, or liquid. K2 is the kind most readily available, but some forms with K1 are also on the market. Newborns, as well as some rare medical circumstances, might require an injection, usually in the form of K1. 

If your healthcare provider has recommended you take both vitamin D and vitamin K, you can use two separate products. However, for convenience, you could opt to take a combination product that contains both vitamins D and K.

Most commonly, combination products use vitamin D3 and the MK-4 or MK-7 forms of vitamin K2, either as a pill or a liquid. Depending on how they are being marketed, such as for bone or heart health, the products might include additional ingredients.

Dosage

It’s not clear whether the dosage for vitamin D or vitamin K should change when the two are taken together. But here's what is known about the dosage for each vitamin:

Vitamin D

Dosing for vitamin D can get a little confusing because two different measurement systems are commonly used. You might get a dose measured in international units (IU) or in micrograms. For reference, 400 IU vitamin D is the same as 10 mcg.

The National Institutes of Health (NIH) recommends people 1-70 years old get around 600 IU (15 mcg) vitamin D a day. This would include intake from dietary and supplement sources. Other medical societies might have different recommendations.

To prevent osteoporosis, a commonly prescribed dose is 800-1000 IU (20-25 mcg) per day. However, some experts recommend higher doses, especially if blood tests have shown that someone is deficient. 

Vitamin K

The NIH notes that 0.12 milligrams (mg), or 120 mcg, daily should provide adequate intake of vitamin K daily for men 19 or older, and 0.09 mg (90 mcg) should do the same for women. This total could include diet and, if needed, supplements.

It’s not clear what the ideal intake should be or if both K1 and K2 might be needed. For instance, these amounts might provide enough vitamin K to prevent bleeds but not for its other potential benefits, like promoting bone health. 

Is It Safe To Take Vitamin D and Vitamin K Together?

There doesn't seem to be any risks from taking the two supplements together. Based on what is know about their physiology, there is no reason to suspect it would be a problem, particularly at lower doses. 

In fact, taking vitamin K along with vitamin D might be safer than taking vitamin D alone. That’s because vitamin K may help guard against some of the problems, like heart disease, that can happen if calcium becomes too high. But that’s not established science yet.

No dietary supplements are totally without risk, though. It’s best to talk with a healthcare provider about possible risks and benefits before starting any new supplements.

Potential Drug Interactions

As with any supplement, vitamin K and D can each interact with certain medications you might already be taking.

The biggest drug interaction for vitamin K would be with warfarin. Vitamin K can make it so that the anticoagulant effect of warfarin is less effective, meaning taking more vitamin K than usual may lead to blood clots. 

Vitamin D is known to interact with several medications, including statins. A high intake of vitamin D can reduce the effectiveness of cholesterol-lowering drugs, such as Lipitor (atorvastatin).

Vitamin D can also interact with thiazide diuretics, drugs that decrease urinary calcium excretion. Because vitamin D supplements increase the amount of calcium your intestines absorb, the combination might cause calcium levels to get too high (hypercalcemia).

It’s best to discuss potential interactions of your full medication list, including over-the-counter medications, with a healthcare provider. They will also know whether any of your medications put you at risk for low vitamin K, vitamin D, or both.

What To Look For

The U.S. Food and Drug Administration doesn’t regulate vitamins and supplements in the same way as drugs. So ideally, pick a supplement with a label saying it has been third-party tested.

This means a group other than the manufacturer has tested the product for its claimed ingredients and any potential contaminants. National Sanitation Foundation (NSF) and the United States Pharmacopeia (USP) are two examples of third-party logos to look for on the product.

Can You Have Too Much Vitamin D3 or Vitamin K?

Vitamin D may be unsafe if taken at very high doses for long periods, especially in people who don't have an underlying deficiency. Very high levels of vitamin D can increase the risks of hypercalcemia, which can be quite dangerous. 

When it occurs, hypercalcemia might cause nausea, constipation, and increased risk of kidney stones. If severe, hypercalcemia can even cause coma or heart rhythm problems.

Although some people might need higher doses for short periods, the NIH recommends 4000 IU (100 mcg) as the maximum amount of vitamin D an adult should take each day through both food and supplements. 

The NIH does not establish an upper limit on the amount of Vitamin K a person should have due to its low potential for toxicity.

Side Effects of Taking a Combination of Vitamins D and K

Researchers haven’t studied much about potential side effects of taking both vitamin D and K. But the combination may have a greater risk of skin rash compared to vitamin D alone.

You should also consider any side effects that either supplement might cause on its own. Both are usually well-tolerated. For some people, vitamin K may cause mild issues like upset stomach, diarrhea, and nausea. 

A Quick Review

Vitamins D and K are two supplements your healthcare provider might say you need. Products that combine the two usually include the D3 and K2 forms of the vitamins. If you need to take both, it is likely safe to do so. In fact, together, the two might be even more beneficial for bone health. Just know the supplements might each interact with medications you are already taking. Before starting vitamin D and vitamin K, talk with a healthcare provider about the potential risks and benefits. They might also be able to recommend the best time of day and dosage to take each supplement.