By Ladd McNamara, M.D.

Everything on this website is for informational purposes only.  Consult your physician before using nutritional supplements.  Please read full medical disclaimer via the link in the footer below.

Most multi-vitamins provide a low daily dose of 400 IU (10 mcg) of vitamin D3, but a quality vitamin-antioxidant supplement will provide you at least 2000 IU (50 mcg).  I consider 2000 IU of vitamin D3 the base dose that every adult should be taking to maintain a good, but not necessarily ideal, vitamin D blood level. So, what is the ideal dose for you?  Well, that depends.

The most optimal dose of vitamin D would be based upon your individual vitamin D blood level, which in turn will depend upon your genetics, your health circumstances, your diet, your lifestyle, and the season, among several other factors.

Vitamin D Blood Level Variables

Your genetics determine vitamin D metabolism in your body, which is why your blood level may differ from another healthy person who weighs about the same as you, despite taking the same dose.  In addition, diseases, medications (particularly statin drugs), stress, and an imbalance of beneficial intestinal bacteria (probiotics), can all lower your vitamin D blood level.

Sources of vitamin D include the sun, food, and supplements.  Barring supplementation, nearly 80% of vitamin D is generated in the skin by stimulation by the sun’s UV-B waves.  With UV-B waves and heat, the skin produces vitamin D3 (cholecalciferol), which is the form found in beef, liver, cheese, and egg yolks; and it is the preferred form of vitamin D that we get in our supplements.  However, vitamin D3 is not the form that is analyzed on a blood test, nor is it the active form used by our cells.

Vitamin D Metabolism and Benefits

Vitamin D3, whether produced by the skin or consumed in food or supplements, is converted by the liver into calcifediol (25-OH-vit D).  This is the most abundant form of vitamin D found in the blood, and the one that is tested to check your vitamin D level.  Yet, calcifediol (25-OH-vit D) is still not the active form of vitamin D.

The kidneys convert calcifediol (25-OH-vit D) into the active form of vitamin D, calcitriol.  Calcitriol is the form of vitamin D that stimulates absorption of calcium from the intestine, and regulates calcium and phosphorus mineralization in the bones.  Vitamin D is important for maintaining strong bones, and avoiding osteoporosis.

The bottom line — supplemental vitamin D3 is ultimately converted into the active form, calcitriol, which has numerous beneficial effects throughout the body, including helping to reduce the risk of diabetes, cancer, heart disease, influenza, asthma, and complications of pregnancy. (For references, and to read more about this, please see my article on the benefits of vitamin D by CLICKING HERE.)

Optimal Vitamin D Blood Levels

The Vitamin D Council recommends maintaining vitamin D levels (calcifediol, 25-OH-vit D) at 50 ng/ml (equivalent to 150 nmol/L).  However, I and many other advanced nutraceutical physicians, consider that to be the very low end of normal, and to help support optimal health, it is important to keep your vitamin D level at higher levels.

Through studying the literature and seeing the results within my medical practice, I have concluded that not only is it quite safe, it is quite clear in my opinion, that the greatest health benefits are obtained by maintaining a vitamin D level between 80 ng/ml – 100 ng/ml (equivalent to 200 – 250 nmol/L).  It is highly advised not to exceed 150 ng/ml (375 nmol/L), as one risks potential vitamin D toxicity.  Therefore, it is best to play it safe, and stick with a maximum acceptable level of 100 ng/ml (250 nmol/L).

Since two people can take the same dose of vitamin D and have  different blood levels, no one can tell you what your blood level will be by a specific dose you take.  Therefore, it is important to check your vitamin D blood level (serum 25-OH vitamin D) a few months after starting vitamin D supplementation, and then annually thereafter.  Consider maintaining your vitamin D level between 75  – 85 ng/ml (188 – 212 nmol/L).

Vitamin D Dose and Blood Levels

A dose of 1,000 IU (25 mcg) of vitamin D3 per day will help 50% of people to maintain a vitamin D blood level of 33 ng/ml (82.4 nmol/L).  Whereas a dose of 2,000 IU (50 mcg) per day will help almost everyone to maintain a blood level of 33 ng/ml (82.4 nmol/L). (1)  This is the dose found in a high quality vitamin/mineral supplement, and why most people need to take an additional stand-alone vitamin D dose.  However, it is not necessarily your ideal target dose.

As a rule of thumb, increasing your vitamin D dosage by 1000 IU (25 mcg) per day, will increase your vitamin D blood level by 10 ng/ml (25 nmol/L).

Increasing your vitamin D dose by 2000 IU (50 mcg) per day, will increase your vitamin D blood level by 20 ng/ml (50 nmol/L).

Depending on the results of your vitamin D blood test, you can increase (or decrease) your daily dose of vitamin D to reach your target level.   It is clear that everyone needs to take at least 4000 IU (100 mcg) per day to maintain the suggested minimum of 50 ng/ml (125 nmol/L).

Optimal Vitamin D Dose

If you are not sure what vitamin D dose is optimal for you, you should consult with your personal physician, and consider starting with a total dose of 6000 IU/day (equivalent to 150 micrograms/day).  Be sure to have your doctor check your vitamin D blood level 2 to 3 months after starting these doses.

If you are currently taking a high quality vitamin-antioxidant supplement, it is providing 2000 IU (50 mcg) of vitamin D3 per day.  Therefore, you could take an additional 4000 IU (100 mcg), to obtain a total of 6000 IU (150 mcg) of vitamin D3 per day.  After two – three months, have your doctor check your vitamin D level. Adjust your dose accordingly.

As a rule of thumb, increasing your vitamin D dosage by 1000 IU (25 mcg) per day, will increase your vitamin D blood level by 10 ng/ml (25 nmol/L).  Increasing your vitamin D dose by 2000 IU (50 mcg) per day, will increase your vitamin D blood level by 20 ng/ml (50 nmol/L).  Results will vary.

If your doctor agrees for your personal health situation, consider maintaining your vitamin D level between 75  – 85 ng/ml (188 – 212 nmol/L), and do not be concerned if your level goes as high as 100 ng/ml (250 nmol/L).

Vitamin K2 Supplementation With Vitamin D

When supplementing with high-dose vitamin D (> 4000 IU, or 100 mcg per day), some doctors have expressed concern that it could be harmful, mostly due to causing hypercalcemia,  high blood calcium. Although there is a very remote risk that very high-dose vitamin D supplementation could cause hypercalcemia, doses as high as 50,000 IU per day have not been shown to cause that problem.  And to further avoid such a concern, vitamin K2 can be added to one’s daily regimen, which would only provide further health benefits.

In a 2019 study, over 4700 hospitalized vitamin D-deficient patients were supplemented with doses of vitamin D, with doses between 5,000 to 50,000 IU (125 mcg to 1,250 mcg) per day.  After vitamin D supplementation, the patients’ vitamin D blood levels ranged from 74 ng/ml to 385 ng/ml (185 to 963 nmol/L).  Among those taking vitamin D supplementation, even the patients taking 50,000 IU (1,250 mcg) day, with the highest blood levels of vitamin D, did not display hypercalcemia.  They had the same calcium blood levels as those taking the lowest doses of vitamin D, which were all within normal range.

Although the concern for taking high-dose vitamin D is mostly unfounded, it still would be a good idea to take additional vitamin K2, not only for how vitamin K2 interplays with vitamin D, but also for the direct benefits of vitamin K2.

One of the main functions of vitamin D is to maintain an adequate and stable calcium blood level. Vitamin D helps stabilize calcium blood levels in at least two ways–

• Vitamin D enhances intestinal absorption of calcium.
• When blood calcium is low, vitamin D assist in mobilizing calcium from your bones.

Although vitamin D helps with absorption of calcium, it does not control where it ends up; and that’s where vitamin K2 comes in.  Vitamin K2 regulates calcium in at least two ways–

• Vitamin K2 activates osteocalcin, a protein that promotes the accumulation of calcium in your bones and teeth.
• Vitamin K2 activates matrix GLA protein, which prevents calcium from accumulating in soft tissues, such as the kidneys and blood vessels.

Given that people with increased vitamin K2 intake have reduced arterial calcification (plaque), it is very likely that vitamin K2 may reduce the risk of cardiovascular disease. Most simply stated, vitamin K2 helps remove calcium from the arteries and deposits it into the bones where it belongs. The dance between vitamin D and K2 is starting to prove to do more to help reduce cardiovascular disease than once was thought.

There is no strong evidence that proves that high-dose (10,000 – 20,000 IU, or 250 – 500 mcg, per day), let alone moderate doses (5000 – 10,000 IU, 125 – 250 mcg) of vitamin D are harmful without an adequate intake of vitamin K2, I think it is wise to take vitamin K2 merely for the benefits that vitamin K2 has to offer.  And should high-dose vitamin D ever show to be a health risk, by you already taking additional vitamin K2, you would be well protected.

If you are taking a high-quality vitamin-antioxidant supplement, you are most likely getting 2000 IU (50 mcg) of vitamin D3 and 60 mcg of vitamin K2.

Consider taking additional 2000 IU (50 mcg) of vitamin D3, and with that, an additional 180 mcg of vitamin K2.

For every 1000 – 2000 IU above this, consider another 180 mcg of vitamin K2.

For example, if you decide to take 6,000 IU (150 mcg) of vitamin D per day, consider taking an additional 360 mcg per day of vitamin K2.  That would be a total of 420 mcg (60 mcg of that from a daily dose of the vitamin-antioxidant tablets).

If you decide to take 8,000 IU (200 mcg) of vitamin D per day, consider an additional 420 mcg per day of vitamin K2.  (That would be a daily total of 480 mcg.)

If you decide to take 10,000 IU (250 mcg) of vitamin D per day, consider taking additional 600 mcg per day of vitamin K2.  (That would be a daily total of 660 mcg.)

Vitamin K2 is perfectly safe at super high doses; well above 10,000 mcg, if not over 50,000 mcg per day.  Many doctors suggest taking 1,000 to 2,000 mcg per day of vitamin K2. The point, taking up to 1,000 mcg per day of vitamin K2 is perfectly safe.

If you are taking warfarin (Coumadin) blood thinner, do not take more than 180 mcg per day of vitamin K2 without consulting your doctor; as the dose of warfarin would most certainly need to be increased to maintain an INR in a therapeutic range.  As long as the daily dose of vitamin K1 and K2 are kept consistent, the dosing of warfarin can be adjusted to maintain a therapeutic INR.

Can I Take Too Much Vitamin D?

Although it is possible to take too much of anything, including vitamin D, taking high doses of vitamin D are not as problematic as once thought.(2) Studies have shown that a daily dose of vitamin D up to 10,000 IU (250 mcg) per day will not cause side effects or toxicity.(3, 4)  To reach toxic blood levels of vitamin D, you would need to take up to 50,000 IU (1,250 mcg) or more per day for a long period of time.(5)

Conclusion

Vitamin D is a very important hormone supplement, one that has not been adequately appreciated until the last ten years or so. Vitamin K2 is emerging to be just as important as vitamin D, and a “health partner” to vitamin D for all the health benefits, not just that to bone and teeth, but to reduce cardiovascular disease as well.

Taking adequate doses of both vitamin D and K2 is a critical component of a broad-spectrum supplement program for reducing the risk of many chronic diseases and maintaining optimal health. Most people are vitamin D and K2 deficient, and taking a generous dose of both vitamin D3 and K2 is required for maintaining optimal vitamin D and K2 blood levels.

Enjoy that bottle of sunshine!

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Everything on this website is for informational purposes only.  Consult your physician before using nutritional supplements.  Please read full medical disclaimer via the link in the footer below.

References

1.  Bischoff-Ferrari HA, et a. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006 Jul;84(1):18-28.
2. Malihi Z, et al. Adverse events from large dose vitamin D supplementation taken for one year or longer.   J Steroid Biochem Mol Biol. 2018 Dec 6. [Epub ahead of print].
3. Glade MJ. A 21st century evaluation of the safety of oral vitamin D. Nutrition. 2012 Apr;28(4):344-56.
4. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999 May;69(5):842-56.
5. Holick MF. Vitamin D Is Not as Toxic as Was Once Thought: A Historical and an Up-to-Date Perspective. Mayo Clin Proc. 2015 May;90(5):561-4.
6. McCullough PJ, et al. Daily oral dosing of vitamin D3 using 5000 TO 50,000 international units a day in long-term hospitalized patients: Insights from a seven year experience.  J Steroid Biochem Mol Biol. 2019 Jan 4. pii: S0960-0760(18)30622-8.
7. Theuwissen E, et al. The role of vitamin K in soft-tissue calcification. Adv Nutr. 2012 Mar 1;3(2):166-73.
8. Hartley L, et al. Vitamin K for the primary prevention of cardiovascular disease.  Cochrane Database Syst Rev. 2015 Sep 21;(9):CD011148.
9. Vossen LM, et al. Menaquinone-7 Supplementation to Reduce Vascular Calcification in Patients with Coronary Artery Disease: Rationale and Study Protocol (VitaK-CAC Trial). Nutrients. 2015 Oct 28;7(11):8905-15.
10. Scheiber D, et al. High-Dose Menaquinone-7 Supplementation Reduces Cardiovascular Calcification in a Murine Model of Extraosseous Calcification.  Nutrients. 2015 Aug 18;7(8):6991-7011.
11. Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study.  J Nutr. 2004 Nov;134(11):3100-5.
12. Beulens JW, et al. High dietary menaquinone intake is associated with reduced coronary calcification.  Atherosclerosis. 2009 Apr;203(2):489-93.
13. Knapen MH, et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial.  Thromb Haemost. 2015 May;113(5):1135-44.

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