Published on September 8, 2021

64% of moderate COVID-19 cases compared to 84% of severe cases had vitamin D levels below 20 ng/ml

Vitamin D is necessary for proper immune function. Multiple studies have shown greater protection against viral infections and upper respiratory diseases with higher vitamin D levels. It is also known that the demand for vitamin D can be increased during times of acute infection, making it even more important to ensure continued adequate intake for the maintenance of vitamin D levels during these times.

With this in mind, findings that higher vitamin D levels are related to greater protection and better outcomes from diseases such as COVID-19 should come as no surprise.

Another Study Shows Low Vitamin D Related to Worse Prognosis

A recent study by Karanova et al., and co-authored by GrassrootsHealth scientist panel member Dr. William Grant, found a significant relationship between low vitamin D levels and severity and death among patients hospitalized with COVID-19. This study included 133 patients whose vitamin D levels at hospital admission ranged from 3 ng/ml to 97 ng/ml. The patients were grouped according to vitamin D level, with 90 patients diagnosed with vitamin D deficiency (less than 20 ng/ml or 50 nmol/L), 37 of which had severe deficiency (less than 10 ng/ml or 25 nmol/L). Normal vitamin D levels were defined as at least 30 ng/ml (75 nmol/L) and were found among only 12 (9%) of the participants in this study. It is important to note that the GrassrootsHealth panel of vitamin D scientists recommends a level of 40-60 ng/ml (100-150 nmol/L).

A further grouping was done based on whether patients were suffering a moderate or severe course of COVID-19 disease. 81% of the patients had a moderate course of disease. Of those suffering a severe course of COVID-19, 35% were severely vitamin D deficient and 15% were mildly vitamin D deficient.

Only one of the 18 patients (6%) who died from COVID-19 had a vitamin D level greater than 20 ng/ml (50 nmol/L).

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Of note, those with severe COVID-19 tended to be older and more often had obesity, diabetes mellitus, and cardiovascular disease (especially coronary artery disease). In fact, this study showed that obesity alone worsened disease prognosis by at least 6 times, and vitamin D deficiency was found to contribute to a greater increase in risk of severity and death than a concurrent diabetes diagnosis.

In Conclusion

Overall, this study concludes that COVID-19 disease severity and death due to COVID-19 were both associated with vitamin D deficiency (levels below 20 ng/ml or 50 nmol/L), with increased significance among those whose vitamin D level was severely deficient, below 10 ng/ml (25 nmol/L). Those with vitamin D levels less than 10 ng/ml had more than 4 times the risk of severe disease and almost 6 times the risk of dying from COVID-19 compared to those 10 ng/ml and higher, after adjusting for age, sex, and comorbidities.

These findings are consistent with previous findings on vitamin D and COVID-19 outcomes, including those from a meta-analysis of 43 studies on vitamin D and COVID-19 that found

  • overall risk of severe COVID-19, defined as the need for intensive care and/or mechanical ventilation, was 160% higher among those with vitamin D levels below 20 ng/ml (50 nmol/L) compared to those whose levels were 20 ng/ml or higher (P<.01).

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  • overall risk of death due to COVID-19 was 22% higher among those with vitamin D levels below 20 ng/ml (50 nmol/L) compared to those whose levels were 20 ng/ml or higher (P<.01).

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For a summary of studies on vitamin D, COVID-19, respiratory infections, and immune function, visit this page.

Are Your Vitamin D Levels OK?

Let us know what your daily vitamin D routine is while testing your levels. Contribute your data as a citizen scientistwhat other discoveries can we make together?

Having and maintaining healthy vitamin D levels and other nutrient levels can help improve your health now and for your future. Choose which to measure, such as your vitamin D, omega-3s, and essential minerals including magnesium and zinc, by creating your custom home test kit today. Take steps to improve the status of each of these measurements to benefit your overall health. You can also track your own intakes, symptoms and results to see what works best for YOU.

Enroll and test your levels today, learn what steps to take to improve your status of vitamin D (see below) and other nutrients and blood markers, and take action! By enrolling in the GrassrootsHealth projects, you are not only contributing valuable information to everyone, you are also gaining knowledge about how you could improve your own health through measuring and tracking your nutrient status, and educating yourself on how to improve it.

Help everyone Move Research into Practice with vitamin D and other nutrients! As a special birthday gift to everyone, in honor of the science, we have created a special scholarship fund for anyone to donate to that will go towards helping others participate. Your donation will allow anyone to get help with funding their participation when they need it.

Text-to-give: Text Daction to 44321 to add to our Scholarship Fund.

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 - Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you're interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!