Vitamin D & Fertility

Although the evidence is suggestive rather than definitive, several studies support an association between higher vitamin D levels and improved fertility, increased live birth, and reduced pregnancy loss.

Background

Lately, several articles about vitamin D have been posted on social media. For example, an article published by EatingWell on August 9, 2026, explains that vitamin D deficiency is common, affecting an estimated 1 billion people worldwide and making it one of the most common nutrient deficiencies. In agreement with many scientific studies, the article suggests that for those at increased risk of deficiency, taking a vitamin D supplement year-round may be the simplest way to help maintain healthy vitamin D levels. Another article published by Health on August 5, 2026, discusses some of the benefits of vitamin D. In addition to mentioning well-known benefits, such as helping with calcium absorption, strengthening bones, lowering inflammation, regulating both the innate and adaptive immune responses, and improving mood, the article also mentions that vitamin D may help lower total cholesterol and low-density lipoprotein (LDL) levels. However, what these articles fail to mention is the important role vitamin D plays in regulating female hormones and, consequently, its potential importance in fertility.

Introduction

One could extrapolate that if inflammation is high, mood is low, and the immune system is weakened—all symptoms associated with vitamin D deficiency—it might be more difficult for a woman to conceive. However, several studies have shown that vitamin D deficiency may directly affect fertility. For example, a prospective cohort study found that women with 25(OH)D levels ≥50 ng/mL had an estimated 35% increase in pregnancy rate compared with those with levels of 30–40 ng/mL, while those with levels <20 ng/mL had a 45% reduction. A randomized controlled trial published in Fertility and Sterility in 2025 examined 2,370 couples seeking infertility treatment. The researchers found that 19.5% of females and 29.9% of males were vitamin D deficient. The trial concluded that “preconception vitamin D status and bioavailability impact fertility among couples seeking infertility therapy.”

“Preconception vitamin D status and bioavailability impact fertility among couples seeking infertility therapy.”

Forms of vitamin D

Vitamin D obtained from sources such as sunlight, foods, and supplements is biologically inactive and it must undergo two hydroxylation steps (a chemical reactions where a hydroxyl group is added) to form its major circulating and active metabolites. The first hydroxylation occurs primarily in the liver, where vitamin D is converted to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second hydroxylation occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol. Although 1,25(OH)2D is the biologically active form of vitamin D, 25(OH)D is the form used to assess a person’s vitamin D status. The primary reason for this is that 1,25(OH)2D has a very short half-life of approximately 4 to 6 hours and is rapidly broken down in the body. In contrast, 25(OH)D has a much longer half-life of approximately 2 to 3 weeks, making it a more reliable indicator of vitamin D stores derived from dietary intake and cutaneous production.

D3 vs D2

According to the Mayo Clinic, there are four main ways to obtain vitamin D: through exposure of the skin to sunlight, by eating foods that naturally contain vitamin D, by consuming foods fortified with vitamin D, and by taking vitamin D supplements. Vitamin D supplements contain two forms: vitamin D2 and vitamin D3.

Although both D2 and D3 increase vitamin D levels in the body, the main difference between them is their source. Vitamin D2 comes primarily from plants and fungi, as well as fortified foods and supplements. Mushrooms, particularly those exposed to ultraviolet (UV) light, can contain significant amounts of D2. Vitamin D3 comes from animal sources and is also produced naturally by human skin in response to sunlight. Vitamin D3 supplements are commonly made from a compound derived from lanolin, a natural, waxy substance produced by the sebaceous glands of sheep and obtained from their sheared wool. Overall, both D2 and D3 can increase vitamin D levels, although D3 generally raises and maintains vitamin D levels more effectively than D2. For those who wish to avoid animal-derived products, vitamin D2 is a suitable alternative.

Adequate levels for fertility and healthy pregnancy

While the National Institutes of Health (NIH) states that a vitamin D blood level of 20 nanograms per milliliter (ng/mL) or higher, measured as 25-hydroxyvitamin D [25(OH)D], is adequate for bone and overall health, several studies suggest that higher levels may be associated with healthier conception and pregnancy outcomes. For example, a 2019 prospective cohort study published in Human Reproduction examined 522 women between the ages of 30 and 44 to determine whether preconception vitamin D levels were associated with the likelihood of becoming pregnant. The study found that women with preconception 25(OH)D levels of at least 50 ng/mL had increased fecundability, while those with levels below 20 ng/mL had reduced fecundability. The researchers also found that for every 10 ng/mL increase in 25(OH)D, fecundability increased by approximately 10%.

A meta-analysis of 12 studies (n=2,352) found that vitamin D supplementation significantly increased clinical pregnancy rates among infertile women, particularly with moderate daily dosing (1,000–10,000 IU) for 30–60 days in women with levels <30 ng/mL.

Pregnancy loss and vitamin D

A 2018 study published in The Lancet Diabetes & Endocrinology investigated the association between preconception serum 25(OH)D concentrations and pregnancy outcomes. The study found that sufficient preconception 25(OH)D levels (≥30 ng/mL) were associated with a greater likelihood of achieving pregnancy and live birth. Among women who became pregnant, higher preconception 25(OH)D concentrations were also associated with a reduced risk of pregnancy loss. Interestingly, 25(OH)D concentrations measured at 8 weeks of pregnancy were not associated with pregnancy loss.

IVF and vitamin D

There is also evidence of an association between vitamin D status and reproductive outcomes in women undergoing assisted reproductive technology (ART). A 2018 systematic review and meta-analysis published in Human Reproduction analyzed 11 cohort studies involving approximately 2,700 women. The researchers found that women with higher or sufficient vitamin D levels, according to the definitions used in the individual studies, were more likely to achieve a positive pregnancy test and live birth than women classified as vitamin D deficient or insufficient.

In another study published in 2014 in the Journal of Clinical Endocrinology & Metabolism, researchers investigated IVF outcomes in women with deficient serum 25(OH)D levels (<20 ng/mL). The study found that women with 25(OH)D levels below 20 ng/mL had a clinical pregnancy rate of 20%, compared with 31% among women with levels of 20 ng/mL or higher. Interestingly, the subgroup of women with 25(OH)D levels above 30 ng/mL had the highest chances of achieving pregnancy.

Acupuncture and vitamin D

While acupuncture cannot directly create or increase vitamin D levels in the body, it may support some of the physiological processes involved in nutrient digestion and absorption. For example, a 2024 study suggests that acupuncture may influence gastrointestinal function and the gut microbiome, potentially supporting overall digestive health.

This may be relevant to vitamin D because vitamin D is a fat-soluble nutrient that requires proper fat digestion and absorption in the small intestine. As noted in a 2025 review published in Frontiers in Cellular and Infection Microbiology, vitamin D absorption is substantially dependent on gastrointestinal health. Conditions that impair fat digestion, intestinal mucosal integrity, or bile-acid function can reduce vitamin D bioavailability and contribute to deficiency.

Because adequate vitamin D status has been associated with reproductive outcomes, supporting the body's ability to properly digest and absorb nutrients may be relevant to fertility. While acupuncture has not been shown to directly increase vitamin D levels or improve vitamin D absorption, its potential effects on gastrointestinal function and the gut microbiome may provide an indirect pathway through which acupuncture could support overall nutritional status and reproductive health.

Conclusion

Vitamin D receptors are found in nearly all cells and tissues of the human body, highlighting the important role this vitamin plays in numerous physiological processes. Vitamin D deficiency may negatively affect the body in multiple ways, including reproductive function. While animal studies have demonstrated a clear association between vitamin D deficiency and impaired fertility, the evidence in humans remains less definitive. Nevertheless, a growing body of human research has found an association between vitamin D status and reproductive outcomes, including pregnancy and live birth rates, both naturally and among women undergoing assisted reproductive treatments.