How to interpret your vitamin D result, common questions, and next steps to take

Vitamin D is essential for the proper functioning of all major systems within our body, including how our cells read and express our DNA. The most accurate measurement of vitamin D status is determined by measuring the amount of 25(OH)D in your blood – this is the measurement received when participants test through the GrassrootsHealth Vitamin D*action project. 

How to read your results

Your latest vitamin D result [total 25(OH)D] is located in the middle of the circle on the left side of the Vitamin D tab on your “my Test Results” page. Next to that is a chart displaying each of your vitamin D results plotted over time. Vitamin D results are posted in ng/ml by default; to switch to nmol/L, click the green button below the chart.

NOTE: The images below are for demonstration only and do not reflect your personal results.

Below this you will find a table your latest and past vitamin D results, including your total 25(OH)D, 25(OH)D2 and 25(OH)D3. The latest results will be at the top.

Are you within your target range?

Our panel of 48 International Scientists recommends a vitamin D level of 40-60 ng/ml (100-150 nmol/L) for the general population, however, some individuals may benefit from levels above 60 ng/ml (see below).

What vitamin D level do you want to aim for?

Different health concerns benefit from different target levels; learn more about differing optimal levels of vitamin D for the prevention of several diseases known as major causes of death here.

Are you below your target vitamin D level?

After getting your vitamin D result, compare where you are at now to where you would like to be. If you are below your target, try using the Vitamin D*calculator to see how much vitamin D might be needed to help you achieve and maintain your target level.

Use the Vitamin D*calculator here

Learn more about how to use the Vitamin D*calculator here

Are vitamin D levels above 60 ng/ml safe?

The recommended range above is for general health and is based on overwhelming evidence on the association between vitamin D and the reduced risk of many diseases including bone diseases (rickets, osteomalacia, and osteoporosis), multiple sclerosis, diabetes, cancer, and many others.

There is evidence that levels above 60 ng/ml may provide additional benefit, especially for breast cancer prevention and treatment of autoimmune diseases. GrassrootsHealth considers levels between 60 and 100 ng/ml (150-250 nmol/L) to be safe and in the high end of a normal range.

Did your level come back higher than expected?

Before changing your daily dose, consider whether a recent change in intake, such as an extra-large dose during a sickness or a recent vacation to a sunny location, may have caused a temporary high level. If this is the case, the vitamin D level will naturally decline back to its baseline or maintenance level.

Learn more about what vitamin D level could be considered “too high,” what can cause a vitamin D result to be higher than expected, and how can you effectively lower your vitamin D level when needed here.

More information on vitamin D toxicity can be found here.

Did your vitamin D result come back lower than you expected with no change in supplement dose?

Learn more about some possible reasons why this could happen and questions to ask if it happened to you here.

Why is your level different from someone else who is taking the same dose?

One of the most important things to understand with vitamin D, and why measurement and re-testing is so important, is the variability in individual dose-response. Learn about several key factors that can influence how your vitamin D level responds to intake, and why it is different for everyone, here.

What is the meaning of the vitamin D2 result?

Vitamin D2 is also known as “ergocalciferol.” It is created by radiating a compound (ergosterol) from the mold ergot. Vitamin D2 is found in mushrooms, in some supplements, and in some fortified foods (such as rice milk and soy milk).

As part of the vitamin D test results reported by GrassrootsHealth, 25(OH) vitamin D2 is an indication of how much vitamin D2 has been ingested or taken. A quick look at the GrassrootsHealth data shows that, of a total of 12,387 latest participant vitamin D test results, only 3% have detectable levels of 25(OH)D2 in their blood.

Learn more about the differences between vitamin D3 and vitamin D2 here.

Interested in utilizing sun exposure to help increase your vitamin D level?

Depending on the circumstances, the body is able to produce enough vitamin D from sunshine to reach levels of 40-60 ng/ml (100-150 nmol/L) – however, doing so is difficult for most. Learn more about how you can utilize the sun for vitamin D production here.

You can also choose indoor UVB devices as an alternative option. Learn more here.

How long should you wait to re-test your level?

Find answers to questions such as “How long will it take to see a change in my vitamin D level?” and “How often should I take my supplement?” along with differences in expectations when taking daily versus bolus doses, here.

Why should you re-test your vitamin D level?

Supplementation does not always provide the expected change in vitamin D level. For example, an analysis of 5,442 GrassrootsHealth participants who completed at least two vitamin D tests showed that two-thirds (67%) reached a vitamin D level of at least 40 ng/ml on their second test – leaving 1/3 of those who re-tested still below the 40 ng/ml target level. It is vital to TEST, ADJUST, RE-TEST and REPEAT to make sure that the daily dose or vitamin D routine is effective at achieving and maintaining the desired target vitamin D level.

What are vitamin D levels of other participants?

A preliminary analysis of the GrassrootsHealth data from 2022 and 2023 (through the middle of December, 2023) shows that

  • in 2022, 20% of the vitamin D results were below 40 ng/ml (100 nmol/L), and 45% were above 60 ng/ml (150 nmol/L), with an average result of 61 ng/ml (152 nmol/L)
  • in 2023 (for results posted through mid-December), 22% of the vitamin D results were below 40 ng/ml and 42% were above 60 ng/ml, with an average result of 59 ng/ml (147 nmol/L)
  • looking at first-time vitamin D test results only, for 2022 and 2023 combined, 38% of the vitamin D results were below 40 ng/ml and 29% were above 60 ng/ml, with an average result of 51 ng/ml (127 nmol/L)

What are vitamin D levels of the general population?

Anywhere between 40-75% of the world’s population is vitamin D deficient. The pie charts below illustrate vitamin D levels in the general US population compared to participants in the GrassroostHealth cohort.

These charts clearly show the difference in distribution of vitamin D levels among adults. Almost 90% of U.S. adults in the NHANES data set had a vitamin D level below the recommended range of 40-60 ng/ml! Those in the GrassrootsHealth cohort have significantly higher levels than those in the NHANES cohort; yet approximately 42% of GrassrootsHealth participants were also below that range.


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