Vitamin D3 + K2 Is Everywhere. Do You Actually Need 5,000 IU?

Vitamin D3 with K2 and MK-7 Metagenics Nutritional Supplement

Before you take a high-potency vitamin D supplement every day, know why you’re taking it

Vitamin D has become one of those supplements people take almost automatically. Somebody tells you it helps your bones, your immune system, your mood, your muscles and possibly everything else, and before long there is a bottle of 5,000 IU vitamin D sitting next to the coffee maker.

Vitamin D really is important. Your body needs it to absorb calcium and maintain healthy bones, and it also plays roles in muscle, nerve and immune function. But vitamin D is fat-soluble, and that matters. This isn't a vitamin where I think the sensible approach is, Well, if 1,000 IU is good, 5,000 must be five times better.

It doesn't work that way.

The Metagenics product I carry contains 5,000 IU of vitamin D3 in each softgel, along with vitamin K1 and vitamin K2 as MK-7. That is a substantial amount of vitamin D, so before I recommend it — or before you decide to take it — I want to know the answer to the same question I've been asking throughout this series:

What are we trying to accomplish?

First, let's straighten out D2, D3, K2 and MK-7

Supplement labels can make this unnecessarily confusing.

Vitamin D comes primarily in two supplemental forms. Vitamin D2 is ergocalciferol. Vitamin D3 is cholecalciferol.Both can raise vitamin D levels, although D3 generally produces a greater and more sustained increase in circulating 25-hydroxyvitamin D.

The Metagenics product I'm discussing uses vitamin D3.

Vitamin K has its own alphabet soup. Vitamin K1 is phylloquinone, the form found largely in leafy green vegetables. Vitamin K2 refers to a group of compounds called menaquinones.

And this is where people understandably get tripped up: MK-7 is not vitamin K7. It is a form of vitamin K2 called menaquinone-7.

So the shorthand for this product is really D3 + K2, with the K2 supplied as MK-7.

What does vitamin D actually do?

Its best-established role is in calcium metabolism and bone health. Vitamin D helps your intestines absorb calcium and helps maintain the calcium and phosphate concentrations needed for normal bone mineralization. It also has established roles in neuromuscular and immune function.

That is quite enough to make vitamin D important without turning it into a cure for everything.

This is something I think gets lost in supplement marketing. A nutrient can have an essential role in a biological process without supplemental megadoses of that nutrient producing additional benefit. Those are two very different ideas.

How much vitamin D do we actually need?

For most healthy adults through age 70, the Recommended Dietary Allowance is 600 IU a day. After age 70, it rises to 800 IU a day. Those recommendations assume relatively little sun exposure.

Vitamin D is unusual because your body can make it when UVB radiation reaches your skin. How much you make varies with season, latitude, age, skin pigmentation, time outdoors and how much skin is exposed.

Food provides some vitamin D too, particularly fatty fish and fortified foods, but there aren't nearly as many naturally rich food sources of vitamin D as there are for some other nutrients.

So yes, supplementation can make sense.

That still doesn't tell us that everybody needs 5,000 IU every day.

This is one nutrient we actually can measure

Unlike magnesium, where assessing total-body status can be surprisingly murky, vitamin D gives us a useful blood marker.

The test generally used to evaluate vitamin D status is 25-hydroxyvitamin D, written as 25(OH)D. That is the main circulating form and the standard starting point when there is a clinical reason to evaluate vitamin D status.

The NIH considers a 25(OH)D level of about 20 ng/mL or higher adequate for most people for bone and overall health, while very low levels are associated with deficiency. It is also worth knowing that there is no universally agreed-upon magical “optimal” level that everybody should chase.

In 2024, the Endocrine Society changed its guidance and recommended against routinely testing vitamin D in otherwise healthy adults who have no particular reason to be tested. It also recommended against routinely taking vitamin D above established dietary recommendations in healthy adults under 75 simply in hopes of preventing disease.

I agree with the principle behind that: don't order a test just because a test exists.

But a person taking a high-potency 5,000 IU daily supplement is a different question. Metagenics itself states on this product that the vitamin D dose exceeds the adult tolerable upper intake level and recommends laboratory monitoring during regular use.

If there is a reason for you to check your vitamin D, the test you generally want is Vitamin D, 25-Hydroxy, Total. You can order that blood test directly through my Ulta Lab Tests practitioner link.

If you order through my Ulta Lab Tests link, I may earn a commission on the test. That helps support the time I spend researching, reviewing and writing about these topics, without adding anything to the price you pay.

Why combine vitamin D with vitamin K?

This combination isn't arbitrary.

Vitamin D helps your body absorb calcium. Vitamin K is needed to activate proteins involved in blood clotting, bone metabolism and calcium-related processes in the body. Vitamin K2, including MK-7, has attracted particular interest because several vitamin K-dependent proteins are involved in bone mineralization and regulation of calcification.

There is real physiology behind combining the two nutrients. What I don't like is the oversimplified sales version that says K2 simply grabs calcium from your arteries and escorts it directly into your bones.

Human physiology isn't a valet-parking service.

Research into vitamin K2 and its effects on bone and cardiovascular outcomes continues. That is different from saying every person who takes vitamin D therefore needs a large dose of K2.

What is MK-7?

Vitamin K2 comes in several forms, including MK-4 and MK-7. MK-7 has a relatively long half-life, which is one reason it is commonly used in supplements.

Dietary sources of K2 are not necessarily foods most Americans eat regularly. Fermented foods can contain menaquinones, and natto — fermented soybeans commonly eaten in Japan — is especially rich in MK-7.

You can probably see why putting it in a softgel has more consumer appeal than telling everyone to develop a taste for natto.

The D3 + K product I carry

The product I carry through my practitioner store is Metagenics Vitamin D3 5000 + K.

Each softgel currently provides 5,000 IU of vitamin D3, 20 mcg of vitamin K1 and 90 mcg of vitamin K2 as MK-7. Metagenics describes the product as supporting bone, cardiovascular and immune health.

What interests me just as much as the front of the label is the warning on the back. Metagenics explicitly states that this product contains vitamin D at a level above the adult tolerable upper intake level and highly recommends monitoring vitamin D levels every 60 to 90 days while consuming it.

That is worth paying attention to.

I carry this product because there are circumstances in which a higher-potency vitamin D supplement makes sense. I don't carry it because I think everyone walking past my website should take 5,000 IU of vitamin D.

I sell the Metagenics products I recommend through my practitioner store and earn the retail margin on those purchases. That helps support the time I spend researching products, reviewing the evidence, developing supplement protocols and writing these articles so you can make more informed decisions, without adding a separate fee for that work.

You can browse my Metagenics practitioner store.

Five thousand IU is a dose worth noticing

The adult tolerable upper intake level for vitamin D is 4,000 IU per day.

That doesn't mean 4,001 IU suddenly becomes toxic. An upper limit is not a cliff you fall off; it is the amount considered unlikely to cause adverse effects in almost everyone in the general population.

There can be legitimate reasons for a healthcare professional to recommend more. But if one softgel contains 5,000 IU, you've already exceeded that general upper limit before counting the vitamin D in a multivitamin, calcium supplement, fortified drink or anything else you happen to be taking.

That's why this isn't a product I would swallow every morning on autopilot.

More vitamin D is not automatically better

Vitamin D toxicity is unusual, but when it happens it generally comes from excessive supplementation rather than food or ordinary sun exposure.

Too much vitamin D can drive calcium levels too high. In serious cases that can cause nausea, weakness, excessive thirst and urination, kidney stones, kidney injury and other complications.

There is an important difference between saying vitamin D is essential and saying therefore I should take as much as possible.

The first is nutrition. The second is lousy logic.

Vitamin K makes one medication issue especially important

If you take warfarin or another vitamin K-antagonist anticoagulant, don't casually add a K2 supplement.

Vitamin K is directly involved in the clotting pathways these drugs are designed to affect. That doesn't mean people using warfarin should eliminate vitamin K from their diets. In fact, maintaining a consistent intake is important. It does mean adding a concentrated vitamin K supplement is something to discuss with the clinician managing your anticoagulation.

Metagenics also advises people who are pregnant or nursing, taking medications or taking anticoagulants to consult their healthcare provider before using this product.

And please look at everything else you're taking

I said this in the magnesium article, and I'm going to keep saying it because it matters.

Your multivitamin may contain vitamin D. Your calcium supplement may contain it. An immune formula may contain it. A protein or meal-replacement drink may contain it. Then you add a 5,000 IU softgel and think you're taking one vitamin D supplement.

You're not. You've created a supplement protocol, whether you intended to or not.

Read the labels and add it up.

So, do you need D3 + K2?

Maybe. A higher-potency D3 + K2 supplement can make sense for the right person and the right reason, but “vitamin D is good for me” isn't enough information to make that decision.

I want to know what you're already taking, why you're considering supplementation, whether there's a reason for the higher dose, whether you're using medications that matter and, when testing is appropriate, what your vitamin D status actually looks like.

That's the point of this whole series. I'm not interested in building you a cabinet full of bottles. I'm interested in helping you understand what is in those bottles and whether there is a reason for you to take them.

What are we trying to accomplish?

Answer that first. Then choose the supplement.

Joyce Strong, RN, BSN
TotalWellCoach.com

Sources

National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals.

National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals.

Endocrine Society. Vitamin D for the Prevention of Disease: Clinical Practice Guideline, 2024.

Metagenics. Vitamin D3 5000 + K — Supplement Facts, Directions and Warnings.

This article is for general educational purposes and is not a substitute for individualized medical advice. Supplements can interact with medications and may not be appropriate for everyone. Discuss supplement use with your physician, pharmacist or another qualified healthcare professional when appropriate, particularly if you take warfarin or another anticoagulant, have kidney disease or disorders of calcium metabolism, take prescription medications, are pregnant or are being treated for a medical condition.

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.