Researchers studied 65 children with POTS (a condition that causes dizziness and fast heartbeat when standing) and compared them to 102 healthy children. They found that children with POTS had lower vitamin D levels. The study discovered that a specific heart rhythm measurement called VLF (very low frequency power) might help doctors predict whether vitamin D treatment will work for each child. When vitamin D was given for 2 months, children with higher VLF readings were more likely to feel better. This finding could help doctors personalize treatment and know which kids will benefit most from vitamin D supplements.

The Quick Take

  • What they studied: Can doctors use a heart rhythm test to predict whether vitamin D will help children with POTS (a condition causing dizziness and rapid heartbeat when standing up)?
  • Who participated: 65 children with POTS (average age 10.6 years) and 102 healthy children (average age 11.2 years) from a hospital in China between November 2023 and May 2024.
  • Key finding: Children with POTS had significantly lower vitamin D levels than healthy children. A heart rhythm measurement called VLF appeared to predict whether vitamin D treatment would work—kids with higher VLF readings were more likely to improve after 2 months of vitamin D treatment.
  • What it means for you: If your child has POTS, doctors may be able to use a simple heart test to predict whether vitamin D supplements will help. However, this is early research, and more studies are needed before this becomes standard practice. Talk to your doctor about whether vitamin D testing makes sense for your child.

The Research Details

This was a case-control study, which means researchers compared a group of children with POTS to a group of healthy children to find differences. They measured vitamin D levels in both groups and looked at heart rhythm patterns using a test called heart rate variability (HRV). The children with POTS were then given vitamin D supplements (800 units per day) for 2 months, and researchers tracked whether their symptoms improved. They used a special heart test that measures how much the heart rate changes at different speeds—the VLF measurement focuses on very slow changes in heart rate.

Understanding which children will respond to vitamin D treatment is important because it could help doctors give the right treatment to the right kids. Instead of trying vitamin D for everyone and hoping it works, doctors could use the VLF test to predict who will benefit. This approach, called personalized medicine, can save time and help children feel better faster.

This study has some strengths: it compared POTS children to healthy controls, used objective measurements (blood tests and heart monitors), and followed children over time to see if treatment worked. However, the sample size was relatively small (65 children with POTS), and it was conducted at a single hospital in China, so results may not apply everywhere. The study was also retrospective, meaning researchers looked back at past data rather than planning the study in advance. More research with larger groups is needed to confirm these findings.

What the Results Show

Children with POTS had significantly lower vitamin D levels (37 nmol/L) compared to healthy children (61 nmol/L). This difference was statistically significant, meaning it wasn’t due to chance. When researchers looked at which factors predicted whether vitamin D treatment would work, they found that the VLF measurement was one of the most important predictors. Children with VLF readings above 1,272 ms² (a specific measurement unit) were more likely to respond well to vitamin D treatment. The test correctly identified 70% of children who would respond to vitamin D and 70% of those who wouldn’t—which is moderately helpful but not perfect.

The study also found that another heart rhythm measurement called SDNN was related to treatment response. Children with POTS reported eight common symptoms including heart palpitations, headaches, cold sweats, blurred vision, chest tightness, dizziness, fainting, and digestive problems. These symptoms improved more in children who had higher VLF readings and received vitamin D treatment. The vitamin D deficiency in POTS children was consistent across the group, suggesting this may be a common feature of the condition.

Previous research has shown that vitamin D deficiency is common in children with POTS, and some studies suggest vitamin D supplements may help. This study adds to that knowledge by suggesting that not all children with POTS will respond equally to vitamin D—some will improve significantly while others won’t. The idea of using heart rhythm measurements to predict treatment response is relatively new and represents a personalized medicine approach that’s gaining attention in pediatric care.

The study was conducted at only one hospital in China, so results may not apply to children in other countries or populations. The sample size of 65 children with POTS is relatively small, which means the findings need to be confirmed in larger studies. The study didn’t include a group that received a placebo (fake treatment), so we can’t be completely sure the improvement was due to vitamin D rather than other factors like time or attention. The VLF test’s 70% accuracy rate means it misses some children who would benefit and incorrectly predicts benefit for others. More research is needed before doctors can confidently use this test in everyday practice.

The Bottom Line

If your child has POTS and low vitamin D levels, vitamin D supplementation may help, especially if a heart rhythm test shows higher VLF readings. However, this research is preliminary, and you should discuss vitamin D treatment with your child’s doctor. The standard recommendation is to correct vitamin D deficiency regardless of the VLF test, but the test might help predict how much improvement to expect. Confidence level: Moderate—this is promising research but needs confirmation in larger studies.

This research is most relevant for children diagnosed with POTS who have low vitamin D levels. Parents of children with POTS symptoms (dizziness when standing, rapid heartbeat, fainting) should discuss vitamin D testing with their pediatrician. This research is less relevant for children without POTS or those with normal vitamin D levels. Adults with POTS should consult their own doctors, as this study focused specifically on children.

In this study, children showed measurable improvement within 2 months of starting vitamin D treatment. However, individual responses vary—some children may improve faster while others take longer. It typically takes 4-8 weeks to see meaningful changes in POTS symptoms with vitamin D supplementation. If your child doesn’t improve after 2-3 months, talk to your doctor about other treatment options.

Want to Apply This Research?

  • Track your child’s POTS symptoms daily using a simple scoring system: rate palpitations, dizziness, and fatigue on a scale of 0-10. Record this weekly in the app to monitor improvement over the first 2 months of vitamin D treatment. Compare scores before and after treatment to see if there’s meaningful change (improvement of 2 points or more suggests the treatment is working).
  • If your child is prescribed vitamin D for POTS, set a daily reminder in the app to take the supplement at the same time each day (consistency improves absorption). Also track water intake and salt consumption, as these affect POTS symptoms. Use the app to log when symptoms are worst (usually when standing up) and best (usually when lying down) to identify patterns.
  • Use the app to create a monthly symptom report comparing the current month to the previous month. Track not just the main symptoms but also secondary effects like energy levels and school attendance. If using the VLF heart test, note the date and result in the app, then monitor whether children with higher VLF readings show better improvement over time. Share these reports with your child’s doctor at follow-up appointments to guide treatment decisions.

This research is preliminary and should not replace professional medical advice. POTS is a serious condition that requires diagnosis and monitoring by a qualified healthcare provider. Do not start, stop, or change any vitamin D treatment without consulting your child’s doctor. The VLF test mentioned in this study is not yet standard clinical practice and should only be used as recommended by your healthcare provider. This study was conducted in China and may not apply to all populations. If your child experiences severe symptoms like fainting, chest pain, or difficulty breathing, seek immediate medical attention.