Can You Take Vitamin K2 With Magnesium?

Quick answer

NIH notes that vitamin K is often sold combined with magnesium, and neither nutrient's fact sheet describes an effect on the other. Magnesium from supplements has an adult limit of 350 mg a day; vitamin K has no limit. People taking warfarin should not start K2 without their doctor.^1,2,3

Key facts

Green leafy vegetables such as spinach provide both magnesium and vitamin K1.^2,3
There is no separate recommended amount for K2. The adequate intake of 90 mcg a day for women and 120 mcg for men covers all forms of vitamin K.³
Half or more of the body's magnesium is in bone, and vitamin K is needed to activate osteocalcin, a protein in bone.^3,4
Long courses of antibiotics can lower vitamin K, and magnesium can keep some antibiotics from being absorbed.^1,2

What is known about the pair

The two often share a capsule. NIH names magnesium, with calcium and vitamin D, among the nutrients most often combined with vitamin K in supplements. Neither NIH fact sheet describes either one changing how the other is absorbed or used, and we found no study that tested the pair.^3,4

Their common ground is bone. Magnesium is part of the structure of bone and takes part in forming it. Vitamin K is the helper for an enzyme that finishes osteocalcin, a bone protein that may be involved in how bone is mineralized and renewed.^3,4

The bone statements, with grades

Both statements are quoted from our ingredient pages and describe roles the nutrients play when intake is adequate. For both, trials of extra amounts on bone density are few or mixed.^3,4

Contributes to the normal structure of bone*^2,4

Moderate evidence

A long-established role of the mineral, described by NIH: half or more of the body's magnesium is held in bone, where it is part of the bone's structure and takes part in bone formation. This is a role of the nutrient. NIH describes the trials of whether extra magnesium changes bone density as few and small, and says more research is needed.

Amount studied: Recommended daily intake from food and supplements

Contributes to the maintenance of normal bones*^3,5

Moderate evidence

Vitamin K is needed to activate osteocalcin, a protein in bone, and NIH reports that the European Food Safety Authority found a cause and effect relationship between dietary vitamin K and the maintenance of normal bone. Supplements beyond a normal intake are another matter: trials are mixed, a 2019 review of 36 randomized trials found no clear effect on bone mineral density in women after menopause once lower quality trials were set aside, and the FDA has not authorized a health claim for vitamin K in the US.

Amount studied: Adequate intake of 90 to 120 mcg a day from food; supplement trials used from 180 mcg of MK-7 to 45 mg of MK-4 a day

K2 forms and amounts

MK-7 is a long-chain menaquinone made by bacteria. Natto, a dish of fermented soybeans, is very rich in it, and MK-7 supplements are often made from natto.^3,6

MK-4 is a short-chain menaquinone. The body makes it from K1 without help from bacteria, and it is found in meat, eggs and dairy foods.³

Both are well absorbed. MK-7 lasts much longer in the blood and, in a head-to-head study, activated more osteocalcin than K1 did.^3,6

No form of K2 has an official target of its own: the adequate intake covers all vitamin K together. Magnesium labels, by contrast, give the elemental magnesium, the mineral itself, and that figure is what counts toward the 350 mg limit for supplements.^2,3,4

Taking them with meals

In a study of five volunteers, blood K1 after spinach eaten with butter was about three times higher than after spinach alone, though still far below the level after a tablet.⁷

A K2 capsule is absorbed the way dietary fat is, so a meal with some fat suits it. Magnesium's share absorbed rises when it is taken in several smaller amounts. Nothing in our sources says the two must be taken at the same time, or apart.^3,8

Legumes, nuts, seeds, whole grains and green leafy vegetables such as spinach provide magnesium, as do fortified breakfast cereals, milk and yogurt.²

Green leafy vegetables are the richest sources of K1. Half a cup of boiled frozen collards has 530 mcg, a cup of raw spinach 145 mcg, a cup of raw kale 113 mcg and half a cup of boiled broccoli 110 mcg.³

What's in ours

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

None of our products contains vitamin K.

Warfarin, antibiotics and other cautions

Warfarin and similar blood thinners work against vitamin K. Do not start, stop or change a K2 supplement, or a multivitamin that contains it, without your doctor, because a change in vitamin K intake changes how well the medicine works.^1,9

Your doctor may want to check on you

Antibiotics can kill the gut bacteria that make vitamin K. Courses longer than a few weeks may lower the amount available to the body, and cephalosporin antibiotics such as cefoperazone might also block vitamin K's action. NIH says vitamin K supplements are usually not needed unless antibiotic use is prolonged and intake is poor.^1,3

Expected from how the two work, not shown in studies

Ask your pharmacist how far apart to take them

Magnesium can bind quinolone antibiotics such as ciprofloxacin and levofloxacin in the gut, so less of the antibiotic is absorbed. The ciprofloxacin label lists magnesium and aluminum antacids, multivitamins and other products with minerals such as calcium, iron or zinc among those that lower its absorption.^4,10

On the medicine's label

Antibiotics touch this pair from two sides: magnesium can keep some antibiotics from being absorbed, and a long course of antibiotics can lower the vitamin K that gut bacteria make. Ask your pharmacist how to fit both supplements around an antibiotic.^3,4

Ask first if you take another blood thinner, such as apixaban, rivaroxaban, clopidogrel or daily aspirin.
Ask first if you take a bile acid sequestrant or orlistat, which lower vitamin K absorption, or a bisphosphonate, a diuretic, an acid reflux medicine, gabapentin or levothyroxine, which magnesium can affect.^1,2
Ask first if you have kidney disease, have had a blood clot, or have a bleeding or clotting disorder.
Ask first if you are pregnant or nursing.

Questions people ask

Can you take vitamin K2, D3 and magnesium together?

Vitamin K is often combined with magnesium or vitamin D, and sometimes both. Our sources describe no effect among the three on each other's absorption, apart from laboratory work in which vitamins D and K competed for uptake. Check each amount: supplemental magnesium has a 350 mg limit, vitamin D a 100 mcg limit, and K2 none.^2,3,11,12

Does K2 with magnesium matter if I take apixaban or rivaroxaban?

Ask your doctor or pharmacist. NIH's interaction warning names warfarin and similar medicines, and the apixaban and rivaroxaban labels mention vitamin K only to say it is not expected to affect how those medicines work in a bleed.^3,13,14

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Sources

*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.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.