Vitamin D and Fertility

By CNY Fertility Updated on

How do vitamin D and fertility relate?  To start, the vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in the reproductive tissues of both men and women. 

Vitamin D, also known as the sunshine vitamin, is produced by the body in response to sunlight.  It can also be consumed through different foods and supplements.  

Recently, research has emerged showing that vitamin D can positively affect both male and female fertility and one’s chances of getting pregnant

This article will review how vitamin D impacts fertility and how low vitamin D or vitamin D deficiency can decrease the chance of conception.  

Fast Facts

  • People are considered at risk of vitamin D deficiency if their serum 25(OH)D concentration is less than 30 nmol/L. 
  • Around 40% of the U.S. population is considered vitamin D deficient.
  • Many studies have shown that vitamin D deficiency is related to reduced fertility and various adverse pregnancy outcomes.
  • Supplementing vitamin D has been linked to improved female fertility and pregnancy outcomes.
  • Studies have shown that infertile men with vitamin D deficiency had significantly lower sperm production and motility compared with men having normal vitamin D status.
  • Vitamin D supplementation can help to increase testosterone levels by up to 25% in one year.

What is Vitamin D

Vitamin D is a fat-soluble vitamin that can be obtained from foods, supplements, and sun exposure .

Vitamin D has many positive biological effects on the body, including reducing inflammation, stimulating the immune system, increasing the absorption of nutrients, and is associated with positive reproductive measurements and outcomes . 

What Is a Normal Vitamin D Level?

Researchers don’t agree on a “normal” or “standard” vitamin D level.  However, they have established a range between vitamin D deficiency and sufficiency.  

People are considered at risk of vitamin D deficiency if their serum 25(OH)D concentration is less than 30 nmol/L.  A level of 50 nmol/L or more is sufficient for most people. The most accurate way to measure vitamin D levels is a 25-hydroxy vitamin D test performed on a blood sample. .  

Research shows that up to 42% of the U.S. population is vitamin D deficient

Check out the chart below to see how different serum 25-hydroxyvitamin D [25(OH)D] concentrations relate to your health as provided by The National Institutes of Health :

nmol/L ng/mL Health Status
<30 <12 Associated with Vitamin D deficiency
30 – <50 12 – <20 Considered inadequate for overall health
≥50 ≥20 Considered adequate for overall health
>125 >50 Linked to potential adverse effects

During an initial fertility screening, a woman’s vitamin D level is usually checked.  A vitamin D test is a basic part of female fertility testing.  Men can also undergo a vitamin D test anytime they complete bloodwork.  A vitamin D test is not as common during male fertility testing.  

The official recommended daily intake levels for vitamin D are relatively consistent across gender, age, and pregnancy status. 

That said, studies show and many doctors recommend that women who are trying to get pregnant, are pregnant, or are lactating should consume higher levels of vitamin D (between 50-100 mcg daily) This is largely due to the fact that vitamin D levels have been shown to be positively associated with many fertility and pregnancy measures and nearly 40% of the population is deficient and must take more to build their vitamin D stores .

Similarly, women who are lactating may also look to increase their vitamin D because a newborn baby’s vitamin D level is largely dependent on the vitamin D status of its mother. 

Other factors can also influence a person’s recommended daily intake and vitamin D level, like their geographic location, which could determine sunlight exposure.  

Check out the figure below to see recommended dietary allowances for vitamin D as published by the National Institute of Health .  :

Age Male Female Pregnancy Lactation
0-12 months 10 mcg (400 IU) 10 mcg (400 IU)    
1-13 years 15 mcg (500 IU) 15 mcg (500 IU)    
14-19 years 15 mcg (500 IU) 15 mcg (500 IU) 15 mcg (500 IU) 15 mcg (500 IU)
19-50 years 15 mcg (500 IU) 15 mcg (500 IU) 15 mcg (500 IU) 15 mcg (500 IU)
51-70 years 15 mcg (500 IU) 15 mcg (500 IU)    
>70 years 20 mcg (800 IU) 20 mcg (800 IU)    

As previously mentioned, these recommended dietary allowances for vitamin D can be achieved by eating certain foods or taking vitamin D supplements.  Keep reading this article for more information on food and supplements.  But for now, let’s dive into how vitamin D and fertility are related!

How Low Vitamin D Effects Female Fertility

Vitamin D deficiency has been associated with a number of female fertility problems, including PCOS, endometriosis, and uterine fibroids . Research suggests that vitamin D impacts several polycystic ovary syndrome (PCOS) symptoms known to negatively affect fertility, like ovulatory dysfunction, insulin resistance, and hyperandrogenism.   Researchers believe that Vitamin D deficiency may also contribute to the pathogenesis of endometriosis due to its anti-inflammatory properties.

Many studies have shown that vitamin D deficiency is related to reduced fertility and various adverse pregnancy outcomes .  Research shows that up to 42% of the U.S. population is vitamin D deficient .  As such, most fertility clinics include vitamin D testing as part of their initial screening process.  If a patient’s results indicate they have low vitamin D or are vitamin D deficient, most doctors will immediately recommend a vitamin D supplement. 

Some research has shown that vitamin D deficiency is associated with lower pregnancy rates, especially for women undergoing in-vitro fertilization treatment (IVF) . This particular study found a significant relationship between vitamin D and implantation, clinical pregnancy, and live birth rates.  Other studies have produced conflicting results, but there appears to be no downside to ensuring appropriate vitamin D levels while trying to get pregnant.  

Supplementing vitamin D has been linked to improved female fertility and pregnancy outcomes.  Research has shown that vitamin D supplementation might improve menstrual frequency and metabolic disturbances in women with PCOS . Vitamin D supplementation has also been shown to improve IVF outcomes, especially for women with PCOS.  In one study, researchers concluded that vitamin D supplementation leads to an improvement in the quality of embryos and a significantly higher clinical pregnancy rate .  

Please note there are also many other supplements that can help to improve the fertility of PCOS patients!

Vitamin D and Male Fertility

The simplest way to measure a man’s fertility is through a semen analysis.  A semen analysis measures several different parameters of sperm to determine its overall quality. Research has shown that low vitamin D status has been associated with impaired semen quality .  This is likely caused by vitamin D’s influence on the testis.  Vitamin D influences hormone production and spermatogenesis (development of sperm) .  

Studies have shown that infertile men with vitamin D deficiency had significantly lower sperm production and motility compared with men having normal vitamin D status . On the flip side, high vitamin D levels have been linked to greater sperm motility .  In addition to supporting sperm motility, vitamin D has also been shown to have a positive effect on overall semen quality .

But semen quality isn’t the only thing that affects male fertility.  Male fertility is also greatly impacted by the primary male sex hormone, testosterone.  Testosterone plays a vital role in the development of male reproductive tissues like the testis.  Unfortunately, men suffering from vitamin D deficiency have been shown to have lower testosterone levels . The good news is that research has shown that supplementing vitamin D can increase testosterone levels.

In one study, researchers treated patients with either a vitamin D supplement or a placebo.  The placebo group saw no change in mean testosterone levels from their baseline measurement to their after-treatment results.  The vitamin D supplementation group saw a significant increase in total testosterone levels from 10.3 nmol/l to 13.4 nmol/m, bioactive testosterone levels from 5.21 nmol/l to 6.25 nmol/l, and free testosterone levels from 0.222 nmol/l to 0.267 nmol/l.  

Mean circulating 25(OH)D concentrations also increased significantly by 53.5 nmol/l in the vitamin D group.  This study showed that vitamin D supplementation could help to increase testosterone levels by up to 25% in one year .  

Vitamin D and Pregnancy

As previously mentioned, babies get their vitamin D from their mothers during both pregnancy and lactation.  Maternal vitamin D insufficiency is associated with childhood rickets and longer-term problems, including schizophrenia and type 1 diabetes.  As such, it is important to ensure that mother’s vitamin D levels are adequate both during pregnancy and while they are breastfeeding. 

In one longitudinal study, researchers looked to measure vitamin D status in healthy pregnant women compared to non-pregnant women of the same age.  Researchers found that pregnant women had lower vitamin D concentrations when compared to non-pregnant women.  They also found that vitamin D status was higher in pregnant women who reported taking multivitamin supplements .  This study showed that vitamin D supplementation can improve vitamin D levels for pregnant women, but is it safe?

In another study, researchers measured the safety of vitamin D supplementation during pregnancy.  For the 350 women in the pregnancy, not a single adverse event was attributed to vitamin D supplementation.  Researchers conclude that vitamin D supplementation is both safe and effective for women throughout pregnancy .  

It is worth emphasizing that vitamin D intake and vitamin D deficiency in pregnant and lactating women are very common worldwide .  At CNY Fertility, we highly recommend supplementing vitamin D, especially if you are trying to get pregnant and your vitamin D levels are low or insufficient. 

Most fertility supplements only contain about 400 IU of vitamin D.  While this may be enough for some women, it may not be enough for others to ensure their vitamin D levels are in a healthy range.  Some research indicates that taking 2000-4000 IU of vitamin D daily is not only safe, but is recommended for women, especially those who are pregnant .  

How to Increase Your Vitamin D Levels

Now that you know how common vitamin D deficiency is and all of the benefits of vitamin D for fertility, let’s discuss how you can get more!

Get Some Sun

Your doctor or parents may have told you to go out and get some sun.  The sun is a wonderful energizing force that is great for many reasons, but the main one is that it helps our bodies produce vitamin D.  When exposed to sunlight, our skin produces vitamin D from cholesterol.  Vitamin D synthesis occurs when UVB rays from the sun hit the cholesterol in our skin cells. The sun provides our skin cells with energy so that the synthesis can occur.  

Although the sun is a great natural source of vitamin D, it can be difficult to ensure adequate levels through sun exposure alone.  Sunlight can be scarce during the winter months depending on where you live. It is also important to note that people with darker skin have more melanin in the epidermal layer of their skin.  Melanin reduces the skin’s ability to produce vitamin D from sunlight.  This explains why people with darker skin are more likely to be vitamin D deficient than people with lighter skin .


Believe it or not, only a handful of foods contain significant amounts of vitamin D.  Most of the foods included in the chart below are fish and are not common fixtures in western diets.  

Food  Quantity Vitamin D content
Salmon 0.5 filet (155g) 815 IU
Herring 1.0 filet (143 g) 306 IU
Canned Tuna 3.5 ounce (100 g) 268 IU
Egg Yolks 1 large (17g) 37 IU

As you can see from the chart above, relying solely on diet to achieve the recommended daily amount of vitamin D from diet alone is extremely difficult.  That is why most fertility specialists recommend vitamin D supplements.  

Take a Vitamin D Supplement

As mentioned throughout this article, vitamin D supplementation has been shown to have many positive effects on both male and female fertility.  Recent studies have also indicated that supplementing vitamin D can increase the chances of pregnancy in couples using fertility treatments .  Other research suggests that vitamin D supplementation may be beneficial for metabolic, endocrine, and fertility aspects specifically for patients with PCOS .  Taking supplements is the easiest and most effective way to ensure you are getting enough vitamin D.

Vitamin D can be taken as its own individual supplement or in combination with other vitamins and nutrients in a fertility supplement. When it comes to finding the best fertility supplements, diversity is key. The ideal fertility supplement contains an extensive blend of ingredients that all work together to maximize fertility.

Choosing A Vitamin D Supplement

The supplements we recommend at CNY Fertility are backed by peer-reviewed journals and clinical fertility care experience and formulated by Board Certified Reproductive Endocrinologists. In addition to containing diverse blends of ingredients shown to improve fertility, Molecular Fertility supplements also contain the most absorbable and bioavailable form of each nutrient.  

For these reasons, and we believe Molecular Fertility vitamins to be the best fertility and vitamin D supplements. 

Vitamin D is included in several of the molecular fertility multivitamins and also as a stand-alone product. See below for more details and recommendations.

The Best Fertility Centric Multivitamins with Vitamin D for Women 

Vitamin D for Female Fertility Supplement

For women who are trying to get pregnant and are looking to increase their vitamin D levels, we recommend Molecular Fertility’s Peak Prenatal and Ovarian Boom.  Each supplement contains 50 mcg or 2000 IU of vitamin D for a combined total of 4000IUs and a host of other nutrients to increase the odds of conception.  

Once pregnancy is achieved, we recommend women continue to take the Peak Prenatal throughout pregnancy and nursing to sustain their vitamin D level and ensure proper mother, fetal and baby health. 

The Best Vitamin D Fertility Supplement for Men

Vitamins to Increase Sperm Motility

For men looking to increase their vitamin D levels, we recommend Molecular Fertility’s Male Preconception+.  This supplement is loaded with vitamin D and other nutrients and antioxidants that are near impossible to obtain from diet alone.  All of the ingredients included in this supplement are known to promote sperm health and overall male fertility.  Male Preconception+ contains 50 mcg of 2000 IU of vitamin D which is enough to support the fertility of most men.  

The Best Vitamin D Supplement

If you have been diagnosed as vitamin D deficient or your vitamin D levels are extremely low, you may wish to consider a stand-alone vitamin D supplement.  We recommend Molecular Fertility’s VESIsorb® Vitamin D3.  

This supplement contain a technologically advanced VESIsorb® delivery system which significantly increases the absorbability and bioavailability of vitamin D. VESIsorb® Vitamin D3 has been clinically shown to have 600% better absorption than traditional Vitamin D supplements. By increasing the absorption and bioavailability of vitamin D, these supplements produce faster and better results .  

The Bottom Line and Vitamin D, Fertility and Pregnancy

Vitamin D is an essential nutrient for many of our body’s biological processes, including fertility. 

Unfortunately, it can be extremely difficult to ensure appropriate vitamin D levels through diet and sun exposure alone.  Nearly 40% of the U.S. population is vitamin D deficient, and women who are pregnant/lactating may need to consume even more vitamin D per day to ensure appropriate levels. 

Supplementing vitamin D is a safe and effective way to get your daily dose of vitamin D to improve both male and female fertility and to improve pregnancy outcomes.  


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