The Holick Protocol: High-Dose Vitamin D Supplements for Quick Recovery

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50,000 IU Weekly for 8 Weeks to Resolve Vitamin D Deficiency

The Holick Protocol is named after Dr. Michael Holick. He is the world-leading expert on vitamin D. Dr. Holick is a pioneer in medicine having conducted the most important scientific research on vitamin D ever after it was discovered. He has a long career in the specialized field, starting in the late 1960s, and has more important articles on the subject than anyone else. He is a prolific writer and the most cited author on vitamin D. Holick also has a few books on the subject, including: The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem.

Dr. Holick is a professor but he is not just a scientist. He is a doctor and endocrinologist who has treated many people for vitamin D deficiency–possibly more than anyone else. So his protocol is based not only on proven science but also decades of experience.

What is the protocol?

The Holick Protocol is short-term, high-dose supplementation of vitamin D. It is 50,000 IU once a week for 8 weeks. It was formalized in 2011 by Holick et al. in Guidelines on Vitamin D Deficiency:

We suggest that all adults who are vitamin D deficient be treated with 50,000 IU of vitamin D2 or vitamin D3 once a week for 8 wks or its equivalent of 6000 IU of vitamin D2 or vitamin D3 daily to achieve a blood level of 25(OH)D above 30 ng/ml.

How popular is it?

As early as 2010, the New York Times reported, “People with a serious vitamin D deficiency are often prescribed weekly doses of 50,000 units until the problem is corrected.”

“Adults are commonly prescribed” this dose for this duration, says the National Kidney Foundation.

It may indeed be the most popular vitamin D recovery protocol in the world. Doctors who were taught by Dr. Holick choose it for their patients. Because many people are tested and classified as deficient, and it is the most tested and well-known protocol, it is the one that is most widely used. You can find questions about it online frequently.

(Screen captures: examples of search engine results for the Holick Protocol)

Is it safe?

After being used regularly for ten years it is basically considered safe when patients are deficient and don’t have contraindications.

Why so much?

Patients who have very low vitamin D levels cannot (typically) recover quickly by taking low amounts of vitamin D supplements. For example, anyone with a level of 5 could take months or years to raise their level if they only took 1,000 IU. But that amount might not even raise the level. It is a simple solution to a common problem.

50,000 per week averages at 7143 per day. Some people take more than this much as a daily amount for maintenance. “50,000” sounds like a lot or much more than typical vitamin daily amounts (e.g., vitamin C, 500 mg).  


Sometimes doctors modify the protocol slightly, e.g., make it 50,000 IU for 6 weeks or 12 weeks instead of 8 weeks. Or they adjust the dose amount to 60,000 IU instead of 50,000 IU.

D3 vs D2

Dr. Holick says his protocol is D2, but he was asked if there’s a difference between D2 and D3.

“We have done several studies,” he said, “demonstrating that vitamin D2 is as effective as vitamin D3 in maintaining blood levels of 25-hydroxyvitamin D.”


Is this protocol safe to follow on your own? Well, most people don’t know they are deficient until their doctor advises them to get a vitamin D test. But you can test on your own with a kit that you can send to a lab. You should have the supervision of a doctor, especially if you are unfamiliar with the toxicity risks.


The main benefit of the high-dose protocol is speed. If you aren’t in pain or don’t have an obvious problem, you could reach the same goal; it would just take longer.

Courtesy Dr. Holick, The Vitamin D Solution

Is it a one-time only protocol?

It depends if you stick with the program. 50K can get you to a good level, but then you need to keep it there. You will have to figure out, e.g., in consultation with your doctor, how much to take regularly (daily or weekly). Here is an example of a woman who had to repeat the process after her level dropped to 8:

Tomorrow I will pick up the 8-week prescription for 50,000 IU to be taken once a week. I can’t wait to get started on it. Here we go again. This is the second time this has happened to me. I need to figure out how to keep my level up there once I get back up there.  

Doctors with experience can estimate, based on your lifestyle, how much vitamin D your body will require for a consistent, healthy level. It could be 2000 IU daily or 5000 IU (or higher). Or you could take a weekly supplement. There are multiple factors to consider, including, of course, sun exposure.


Sometimes patients mishear or misremember the frequency. It is WEEKLY, not daily. 50,000 IU weekly would be considered generally safe short-term. 50,000 IU daily would be risky, especially if indefinitely; unless there was some issue, e.g., absorption, which required higher doses.

In one reported case,1 a woman was prescribed 60,000 IU weekly, but she mistakenly thought the doctor said daily. So she took 60,000 IU daily for four months. Her vitamin D level skyrocketed to 746 ng/mL.

What are the contraindications?

It’s good to get your calcium checked before and after a high-dose protocol. The biggest risk of high-dosing on vitamin D is calcium level rising beyond the normal range. Anyone with hyperparathyroidism especially should be under direct supervision of a doctor or specialist.

“Be careful not to overdose on vitamin D! Have  a doctor check you first to make sure you are not hyperparathyroid. This was the cause of my low vitamin D. Taking too much vitamin D when you are hyperparathyroid can be very dangerous! I started taking 5000 IU a day and almost ended up stroking out. Not to mention, I became extremely dehydrated and constipated (two clear signs of overdose). Just be careful!” (Source: Gina, Amazon book review, May 29, 2017. [Oct. 30, 2021].)

The blogger at the Evolution Psychiatrist also has a word of caution:

Four of my patients have developed high calcium with adequate D supplementation to bring the levels above 20 ng/ml. Three of them were found to be hyperparathyroid, and parathyroid tumors were found and later removed…

I measure calcium along with vitamin D, and if the calcium pops above 10.2 with supplementation, I’m very quick to refer the patient back to the primary care doctor for further work-up. Having seen so many cases so recently, I wouldn’t recommend supplementing [anyone with] super-low D (particularly below 20, which is low enough that hyperparathyroidism can be masked by the low D level) aggressively without measuring calcium along with it.

If you have normal levels (say 30 or above) moderate supplementation of 1000-2000 IU daily is probably fine, because if you had hyperparathyroidism, you would already know it, but keep measuring.

Dr. Soram Khalsa

“If my patients’ blood test shows their 25D level to be below 20 ng/ml,” says Dr. Soram Khalsa, author of The Vitamin D Revolution, “this is obviously extremely low. I treat these patients in the way that Dr. Michael Holick has described in his writings and lectures. 

“Specifically, I will prescribe 50,000 IU of vitamin D per week for eight weeks. In my office, I will do this by giving patients one prescription-strength vitamin D3 pill containing 50,000 units per week.

“When my patients tell their friends or any other doctor they may know that I am giving them 50,000 IU a week, their eyes bug out! Those who are not familiar with the current medical literature fear that such a large dose will be toxic.

“In fact, it actually averages out to less than 8000 IU per day, which will never make an otherwise healthy person with vitamin D deficiency toxic over eight weeks.

“Because vitamin D is fat soluble and stored in the body—and specifically 25-hydroxyvitamin D has a half-life of approximately two weeks in the body—this once-a-week dose is very effective but not always easy for my patients to remember.

“However, an equally good way to take 50,000 units a week would be to take 5000 IU of vitamin D per day for eight weeks; and also take an extra 5000 IU pill every Monday, Wednesday, and Friday (so you would take a total of 10,000 units on those three days).”2

Dr. Caroline Fife

Dr. Caroline Fife is an expert at treating wounds. She tells the story (warning: graphic) about one of her patients who had a wound that would not heal. She suspected a deficiency.

“So I drew a vitamin D level,” she said.

It was only 17 ng/mL.

“I prescribed 50,000 units once a week for 12 weeks,” she recalled. “Check out this photo of the wound after only THREE WEEKS of vitamin D supplementation. It’s a different wound entirely! After two failed operations, in three weeks he is healing, with only one small intervention.”3


The speed of the 50K plan is documented. Here is an example showing level changes of children after eight weeks on the protocol from a trial4 testing vitamin D with magnesium:

(Courtesy BMC Pediatrics)

After eight weeks

The term limit of the protocol needs to be taken seriously. The high dosage of 50,000 IU should not continue indefinitely. People have been known to get into routines with daily supplements and stick with them. 

For example, there’s a reported case5 of a 74-year-old woman who took 50,000 IU weekly for two weeks and did not stop; she continued to take it weekly for 4 years.

What happened? She got calciphylaxis. Her calcium was “only mildly elevated (10.8 mg/dL),” doctors noted, “and her serum 25-hydroxyvitamin D was only 43 ng/mL.”

They blamed the calciphylaxis on the supplements, “as it has been shown to be a risk factor in calciphylaxis.”

“She did not have any underlying renal disease,” they explained, “which is often the case with calciphylaxis.” Besides her obesity, her only other risk factor they identified was the weekly dosage of D3.

After it ends, then what?

The expectation after 50,000 IU for eight weeks is the patient will have no longer be deficient. Typically a blood test is done to confirm the success. Then the goal is to keep the level from falling back into deficiency using a regular dose, either weekly or daily.

(Graph courtesy Texas Tech University Health Sciences Center)

Just as levels can be raised fairly quickly, they can also fall quite quickly. Above is an example of a dropoff after a patient stopped taking her supplements.

The maintenance dose initially is an estimate based on the target level as well as the patient’s health, age, weight and lifestyle. Typically it would be a dose between 1000 IU and 10,000 IU.

Additional tests would follow weeks or months later to determine if the maintenance dose was good or needed to be adjusted.

Next: The Optimal Vitamin D Maintenance Dose

  1. Chakraborty, S., Sarkar, A. K., Bhattacharya, C., Krishnan, P., & Chakraborty, S. (2015). A nontoxic case of vitamin D toxicity. Laboratory medicine, 46(2), 146–e31.
  2. Soram Khalsa, The Vitamin D Revolution: How the Power of This Amazing Vitamin Can Change Your Life, 2010, p. 143.
  3. Caroline Fife, “The Vitamin D Deficiency Epidemic (… and, yes, that is a pulsating Dorsalis Pedis artery),” Jan. 23, 2018. [Oct. 30, 2021].
  4. Hemamy, M., Pahlavani, N., Amanollahi, A., Islam, S., McVicar, J., Askari, G., & Malekahmadi, M. (2021). The effect of vitamin D and magnesium supplementation on the mental health status of attention-deficit hyperactive children: a randomized controlled trial. BMC pediatrics, 21(1), 178.
  5. Gorris, M. A., Arora, H., Lieb, D. C., & Aloi, J. A. (2017). A Word of Caution When Prescribing High-Dose Vitamin D. The American journal of medicine, 130(4), e129–e130.

“She was started on a vitamin D supplementation at 50,000 units once per week (IV) and within 2 weeks she started to see a decrease in her sleepiness and fatigue.” Michel Breus, “Vitamin D: Daytime Energy the Old Fashioned Way,” Jan. 20, 2011. [Nov. 5, 2021].

Jetty, V., Glueck, C. J., Wang, P., Shah, P., Prince, M., Lee, K., Goldenberg, M., & Kumar, A. (2016). Safety of 50,000-100,000 Units of Vitamin D3/Week in Vitamin D-Deficient, Hypercholesterolemic Patients with Reversible Statin Intolerance. North American journal of medical sciences, 8(3), 156–162. 

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