How Much Vitamin D Should You Take?

March 24, 2023

The last blog, “Vit D Reference Ranges and How They Were Determined,” reviewed how “normal” ranges of vitamin D were determined, the ranges reported to support basic human physiology, the upper limit of dosing and the call from experts to raise the upper limit.

The initial idea to investigate vitamin D sounded straightforward and was to bring clear scientific evidence on the topic.  What has been uncovered is far from clear with confusion, misconceptions, and myths reigning the literature.  Minimal scientific data supports the decades long thought form believed by the medical establishment and lay people that vitamin D is one of the most toxic fat-soluble vitamins and one should be careful not to take too much vitamin D.

What is clear, and is based on credible scientific literature is: Vitamin D is one of the least toxic fat-soluble vitamins and high doses can be used to help prevent and treat disease.

As there is no absolute consensus on the normal reference ranges of vitamin D, you may be wondering how much you should take.

Are Serum Levels Meaningless?

As mentioned in the previous blog, the serum range to support basic human physiology is reported to be 40-60 ng/mL.  Once you know your vitamin D level, you can individualize your dose, but should we base supplementation dosages on serum values at all?

The first question when determining your vitamin D dosage should likely be the goal:

  • Are you aiming to meet basic physiological needs of the body?
  • Are you aiming to prevent disease?
  • Are you aiming to treat disease?

Higher dosages are required to prevent and treat disease. At the very least, if using the reported range to support basic human physiology, once you are in that range, your maintenance dose can be adjusted accordingly. The optimal daily dose is highly individualized.

Problems with aiming for a specific serum level are:

  • There is no specific serum level target to prevent disease
  • There is no specific serum level target to treat disease
  • Each individual’s target level is different depending on genetics and how vitamin D is metabolized and used by the body. For example:
    • Patient A may reverse their autoimmune disease by taking high doses of vitamin D with a resultant serum level of 200 ng/mL
    • Patient B may reverse the same autoimmune disease by taking high doses of vitamin D but have a resultant serum level of 100 ng/mL

In this regard, serum levels are essentially meaningless. The patient’s individual clinical response to vitamin D should dictate the dose.

Vitamin D Dosage Based on Parathyroid Hormone (PTH) Levels?

In a 2013 study, a high dose vitamin D protocol termed the Coimbra protocol in which daily therapeutic doses ranged from 35,000 – 300,000 IU taken long term has shown to be clinically effective in the treatment of autoimmune diseases.   While serum vitamin D levels were monitored, the authors state in a 2022 study of the protocol, “…the degree of the increase in 25(OH)D serum levels during the treatment was not used for evaluation of both efficacy and side effects…”

Vitamin D levels were not used to monitor response or for dosage adjustments. The patients got better with high dosages.   Their improvement was not based on patient’s serum levels.

Dosage was adjusted according to parathyroid hormone (PTH) activity because as vitamin D goes up, PTH goes down.  For vitamin D to work at maximum potential according to the protocol, it requires PTH levels to be kept at the lowest normal limit.  This is an example of one of the high dose protocols based on parathyroid hormone (PTH) activity

In this regard, the optimal dosage per individual should not be dependent on serum values of vitamin D but should be dependent on parathyroid function, clinical goals and clinical improvement.

Dosing Based on Serum Levels

Though the amount of supplementation required to raise your serum levels are dependent on different factors, the following table estimates the expected increase in serum levels per dosage after 2-3 months:

The problem with such low doses is how long it takes to raise serum levels. Anecdotally at RMC, patients taking 50,000 IU once a week leads to achievement of vitamin D serum levels between 50-100 ng/mL. This coincides with the following from a recent review:

  • A healthy, 70 kg adult would require 4,000-7,000 IU per day or 50,000 IU weekly to maintain a serum level above 50 ng/mL
  • For people with low BMI or low body fat, 50,000 IU once in two weeks is required to maintain a serum level above 50 ng/mL
  • Elderly, overweight and obese individuals require 2-4-fold higher amounts
  • Those with comorbidities and immunocompromise require much higher doses
  • High loading doses exceeding between 100,000 – 500,000 IU take 3-4 days to raise serum levels and maintain a higher level for up to 3 months

At this point, there is no evidence to answer the following question: Is it better to give lower daily doses of vitamin D vs. higher doses once per week?

Tips for Supplementing vitamin D

When supplementing, be sure to take high quality vitamin D3 as studies show it to be more efficacious than vitamin D2. There are other important factors to consider:

Conclusion

  • High dose vitamin D supplementation is required to prevent and treat disease versus lower maintenance doses.
  • Rather than aiming for a particular serum value,  optimal dosage per individual should be dependent on clinical goals, clinical improvement and consideration of parathyroid function.
  • Once your individual goal or improvement is achieved, a maintenance dose should be considered.

Is Toxicity A Concern with High-Dose Vitamin D?

As we need higher doses to treat disease, the fear is we may become toxic from too much vitamin D.    What defines vitamin D toxicity?  Why are doctors telling their patients to reduce their intake? The next blog will dive into the research on vitamin D toxicity.

Have an Awesome Day,   Dr D

Posted in Vitamin D