Researchers studied 148 women trying to conceive and found that those with uterine fibroids (non-cancerous growths in the uterus) had significantly lower vitamin D levels than women without fibroids. The study compared 74 women with fibroids to 74 women without them and measured their vitamin D levels. Women with fibroids had vitamin D levels that were about one-third lower than the control group. This connection remained even after accounting for body weight and season. While this suggests vitamin D deficiency may play a role in fibroid development, researchers emphasize that more studies are needed to prove this relationship and understand what it means for treatment.

The Quick Take

  • What they studied: Whether women with uterine fibroids have lower vitamin D levels compared to women without fibroids, especially in those struggling to get pregnant
  • Who participated: 148 women aged 18-45 years visiting an infertility clinic. Half had confirmed fibroids (non-cancerous growths in the uterus), and half did not. Both groups were similar in age and weight.
  • Key finding: Women with fibroids had vitamin D levels about 33% lower than women without fibroids (41.4 vs 62.0 nmol/L). This difference was statistically significant and remained true even when researchers adjusted for weight and season.
  • What it means for you: If you’re struggling to get pregnant and have fibroids, getting your vitamin D levels checked may be worth discussing with your doctor. However, this study shows an association, not proof that low vitamin D causes fibroids. More research is needed before making treatment decisions based solely on this finding.

The Research Details

This was a case-control study, which means researchers compared two groups of women: those with fibroids and those without. They looked backward at medical records from July 2019 to February 2024 at a fertility clinic in Turkey. All participants were women aged 18-45 trying to conceive. The researchers measured vitamin D levels in blood samples and compared them between groups using statistical tests. They also adjusted their analysis to account for body weight and the season when blood was drawn, since vitamin D levels naturally vary by season due to sun exposure.

This research approach is useful because it allows researchers to compare vitamin D levels between women with and without fibroids relatively quickly and affordably. By adjusting for factors like weight and season, the researchers could isolate the relationship between vitamin D and fibroids more clearly. However, because this is a case-control study looking backward in time, it can show association but not definitively prove that low vitamin D causes fibroids.

The study had equal-sized groups (74 in each), which is good for comparison. The groups were similar in age and weight, reducing confounding factors. The researchers used appropriate statistical tests and adjusted for important variables. However, the sample size is moderate, and the study was conducted at a single clinic in one country, which may limit how broadly the findings apply. The study is recent (2024-2025) and published in a peer-reviewed journal, suggesting it met scientific standards for publication.

What the Results Show

The main finding was striking: women with fibroids had significantly lower vitamin D levels than women without fibroids. The average vitamin D level in the fibroid group was 41.4 nmol/L compared to 62.0 nmol/L in the control group—a difference of about 20.6 nmol/L. This difference was highly statistically significant (p < 0.001), meaning there’s less than a 0.1% chance this difference occurred by random chance. When researchers adjusted their analysis for body weight and season (factors known to affect vitamin D), the difference remained significant, suggesting the vitamin D-fibroid connection is real and not just explained by these other factors.

Interestingly, vitamin D levels did not differ based on fibroid characteristics. Women with a single fibroid had similar vitamin D levels to those with multiple fibroids. Vitamin D levels also didn’t vary based on where the fibroids were located in the uterus (inside the muscle wall versus on the outer surface). Additionally, vitamin D levels showed no correlation with fibroid size. These findings suggest that if vitamin D plays a role in fibroids, it may be more important in their initial development rather than their growth or multiplication.

This study adds to growing evidence that vitamin D may be involved in fibroid development. Previous research has suggested links between vitamin D deficiency and various reproductive health issues. This study is one of the first to specifically examine this relationship in women with unexplained infertility, filling a gap in the research. The findings align with biological research showing that vitamin D plays roles in cell growth regulation and inflammation, both of which are implicated in fibroid formation.

The study has several important limitations. First, it’s relatively small (148 women total) and conducted at a single clinic, so results may not apply to all populations. Second, it’s a case-control study looking backward, so it can’t prove that low vitamin D causes fibroids—only that they’re associated. Third, the study didn’t measure vitamin D supplementation history or sun exposure directly, which could affect results. Fourth, all participants were women trying to conceive, so findings may not apply to women with fibroids who aren’t trying to get pregnant. Finally, the study is observational, meaning researchers didn’t randomly assign people to vitamin D levels; they just measured what was already there.

The Bottom Line

Based on this research, if you have fibroids and are trying to conceive, discussing vitamin D testing with your doctor is reasonable (moderate confidence). General vitamin D supplementation to normal levels is already recommended for overall health by many health organizations. However, don’t assume that correcting vitamin D deficiency will resolve fibroids or infertility—this study shows association, not causation. Any decisions about supplementation should be made with your healthcare provider based on your individual situation.

This research is most relevant to women aged 18-45 trying to get pregnant who have been diagnosed with fibroids. It may also interest women with fibroids who are experiencing infertility. Women without fibroids or those not trying to conceive should not assume these findings apply to them. Anyone considering vitamin D supplementation should consult their doctor first.

If vitamin D deficiency is contributing to fibroids, correcting it would likely take months to show effects, not weeks. Vitamin D supplementation typically takes 2-3 months to significantly raise blood levels. Any effects on fibroid development or fertility would likely take even longer to observe. This is a long-term consideration, not a quick fix.

Want to Apply This Research?

  • Track your vitamin D supplementation (if recommended by your doctor) and your vitamin D blood test results over time. Record the date, dosage, and any symptoms related to fertility or fibroid-related issues monthly.
  • If your doctor recommends vitamin D supplementation, set up a daily reminder in your app to take your supplement at the same time each day. Log your intake to maintain consistency, which is important for raising vitamin D levels effectively.
  • Plan to retest vitamin D levels every 3-6 months if supplementing, and track any changes in symptoms or fertility markers. Note seasonal variations and sun exposure patterns, as these naturally affect vitamin D levels. Share this data with your healthcare provider during follow-up appointments.

This research shows an association between low vitamin D and fibroids in women trying to conceive, but does not prove that vitamin D deficiency causes fibroids. This summary is for educational purposes only and should not replace professional medical advice. Do not start, stop, or change any vitamin D supplementation without consulting your doctor first. If you have fibroids or are struggling to conceive, work with a qualified healthcare provider to develop an appropriate treatment plan tailored to your individual situation. This study was conducted in a specific population and may not apply to all women.