Scientists in Korea discovered a better way to measure vitamin D in people’s blood. They tested over 11,000 Koreans and found a special form of vitamin D called 3-epi-25-OH-D3 that hadn’t been measured before in large studies. This new measurement method is more accurate and helps doctors understand vitamin D levels better. The study shows that this special form of vitamin D is connected to regular vitamin D levels, and it’s important to measure it correctly when checking if people have enough vitamin D.

The Quick Take

  • What they studied: Whether a new, more accurate method can measure all forms of vitamin D in Korean people’s blood, including a special form scientists hadn’t measured before in large groups
  • Who participated: 11,744 Korean people (5,193 men and 6,551 women) ranging from age 10 to 80 years old, with an average age of 53, as part of a national health survey
  • Key finding: Scientists found a special form of vitamin D (3-epi-25-OH-D3) in Korean people’s blood for the first time in a large study. This form made up about 2-24% of total vitamin D, depending on how much vitamin D people had overall. The new measurement method was accurate and reliable.
  • What it means for you: Doctors may now get more accurate vitamin D test results when they use this new measurement method. This could help them better understand if you have enough vitamin D, though more research is needed to know if this changes how doctors treat low vitamin D.

The Research Details

Researchers used a special laboratory technique called ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to measure vitamin D in blood samples from thousands of Korean people. This technique is like a super-precise scale that can separate and identify different forms of vitamin D that regular tests might miss. The study included people of different ages and genders from a national health survey that happened between 2022 and 2024.

The scientists measured three different forms of vitamin D in each person’s blood: the special form (3-epi-25-OH-D3), the main form (25-OH-D3), and another form (25-OH-D2). They then compared the amounts of each form between men and women, and between different age groups, to see if there were any patterns.

This research matters because vitamin D tests are very common, and doctors use them to decide if people need vitamin D supplements. If the old measurement methods were missing this special form of vitamin D, the test results might have been incomplete or misleading. By measuring all forms of vitamin D accurately, doctors can get a clearer picture of people’s vitamin D status and make better decisions about treatment.

This study is strong because it included a very large number of people (over 11,000) from a national health survey, which means the results likely represent the Korean population well. The laboratory method used is one of the most accurate available for measuring vitamin D. However, this study only looked at Korean people, so the results might be different in other populations. The study was descriptive, meaning it showed what vitamin D levels look like in Korea, but it didn’t test whether measuring this special form of vitamin D actually changes how doctors treat patients.

What the Results Show

The special form of vitamin D (3-epi-25-OH-D3) was found in all Korean people tested, with amounts ranging from very small (0.50 ng/mL) to 15.66 ng/mL, with an average of 1.15 ng/mL. This special form made up about 2% of total vitamin D in people with low vitamin D levels, but jumped to about 24% in people with high vitamin D levels.

The amount of this special form was very similar between men and women, showing that gender doesn’t affect how much of this form people have. However, vitamin D levels did change with age, suggesting that older or younger people might have different vitamin D patterns.

There was a strong connection between the special form and the main form of vitamin D (they moved together about 77% of the time), which makes sense because they’re related forms. This strong connection helps prove that the new measurement method is working correctly.

The study found that the percentage of the special form of vitamin D increased as people’s total vitamin D levels increased. People with the highest vitamin D levels had the highest percentage of this special form. This pattern was very clear and statistically significant, meaning it’s unlikely to be due to chance. The study also showed that the new measurement technique was reliable and consistent when measuring the same samples multiple times.

This is the first large-scale study to measure this special form of vitamin D (3-epi-25-OH-D3) in Korean people. Previous studies in other countries have found this form exists, but this is the first time it’s been included in a major national health survey. The findings are consistent with smaller studies from other countries that showed this special form exists and is connected to regular vitamin D levels.

This study only looked at Korean people, so the results might not apply to other ethnic groups who may have different vitamin D patterns. The study measured vitamin D at one point in time, so we don’t know how these levels change in the same person over months or years. The study didn’t look at whether measuring this special form of vitamin D actually helps doctors treat patients better or improves health outcomes. Additionally, the study didn’t examine why this special form increases with higher vitamin D levels or what it means for people’s health.

The Bottom Line

If you’re getting a vitamin D test, ask your doctor if they’re using the newer, more accurate measurement method (UPLC-MS/MS). This method may give more complete results. However, the current recommendations for vitamin D levels from health organizations haven’t changed based on this research, so talk to your doctor about what your vitamin D level means for your health. (Confidence: Moderate - this is new research that needs more study)

This research is most important for doctors and laboratories that measure vitamin D, as it shows them a better way to test. People who have had vitamin D tests or are concerned about vitamin D deficiency should know that more accurate testing methods are becoming available. This is especially relevant for people in Korea, but the findings may eventually apply to other populations. People with conditions that affect vitamin D absorption (like celiac disease or cystic fibrosis) should be aware of improved testing methods.

This research doesn’t directly affect how quickly you’d see benefits from vitamin D supplements, as it’s about measurement accuracy rather than treatment. However, more accurate testing might help doctors identify vitamin D problems sooner, which could speed up treatment. If your doctor recommends vitamin D supplements based on these more accurate tests, you might notice improvements in energy, bone health, or mood within weeks to months, depending on how deficient you were.

Want to Apply This Research?

  • Track your vitamin D test results over time, noting the date, the lab that performed the test, and the total vitamin D level reported. If your lab uses the newer UPLC-MS/MS method, note that as well. This helps you and your doctor see trends in your vitamin D status.
  • If you’re taking vitamin D supplements based on test results, use the app to log your daily supplement dose and any symptoms you notice (energy levels, mood, bone or muscle aches). This helps you track whether supplementation is working for you.
  • Set reminders to get your vitamin D tested annually or as recommended by your doctor. Track the results in the app and compare them year-to-year. If you’re supplementing, monitor whether your levels are improving over time. Share these trends with your doctor to adjust your supplement dose if needed.

This research describes a new laboratory measurement method for vitamin D and does not establish new clinical guidelines for vitamin D treatment or supplementation. The findings are specific to the Korean population and may not apply to other groups. If you have concerns about your vitamin D levels or are considering vitamin D supplementation, consult with your healthcare provider. Do not change your vitamin D supplementation or treatment based solely on this research. Your doctor should interpret your vitamin D test results in the context of your individual health situation, symptoms, and medical history.