Vitamin D and Fertility

We discuss various nutrients and dietary supplements in this article that may or may not be helpful. If you purchase recommended products, services, or treatments, it may benefit CNY Fertility financially. Read more about our financial relationships here. The supplements discussed in this article are not intended to treat, cure, or prevent any disease. If you are pregnant, take any medications, or have been diagnosed with a medical condition, consult with a healthcare provider before taking any dietary supplement.

Vitamin D and Fertility

How do vitamin D and fertility relate?  To start, 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 levels are highly associated with 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 levels or vitamin D deficiency may 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 levels are associated with female fertility and healthy pregnancy outcomes.
  • Supplementing vitamin D has been shown to improve female fertility and pregnancy outcomes.
  • Studies have shown that vitamin D levels are correlated with sperm production and motility.

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 levels of 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 level for vitamin D is 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.  Nearly 40% of the population is deficient and it takes time to restore 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 levels have been positively correlated with many aspects of female fertility and pregnancy outcomes.   

Significantly, research also shows that up to 42% of the U.S. population is vitamin D deficient   As such, vitamin D levels are often measured during an assessment of female fertility.

But don’t worry if you are like one of the millions of Americans who are Vitamin D deficient. Supplementing vitamin D is an effective way to raise Vitamin D levels and has been shown to support female fertility, embryo quality, and pregnancy outcomes when a deficiency is present.   

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 measures of several semen parameters, including sperm count and motility.   This is likely caused by vitamin D’s influence on the testis.  Vitamin D influences hormone production and spermatogenesis (development of sperm).

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 other aspects of sperm quality.

One way in which Vitamin D may support healthy sperm is through assisting in the production of Testosterone and supporting healthy testosterone levels. In one study, men supplemented with Vitamin D or a placebo.  The placebo group saw no change in mean testosterone levels from their baseline measurement to their after-supplementation 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 levels are associated with a variety of childhood health outomes.  As such, it is important to ensure that a 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 help support healthy vitamin D levels for pregnant women.

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 many 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. 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 possibly the 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

Choosing A Vitamin D Supplement

At CNY Fertility, we created Molecular Fertility our own line of supplements designed to help support fertility. 

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 support healthy 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 support egg health and female fertility.  

Once pregnancy is achieved, we recommend women continue to take the Peak Prenatal throughout pregnancy and nursing to sustain vitamin D levels and to encourage 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 support healthy sperm quality and male fertility. The Male Preconception+ contains 50 mcg of 2000 IU of vitamin D.

The Best Stand Alone Vitamin D Supplement

If you prefer a stand-alone vitamin D supplement, we recommend Molecular Fertility’s VESIsorb® Vitamin D3.  

This supplement contains a technologically advanced VESIsorb® delivery system which has been demonstrated to significantly increase the absorbability and bioavailability of difficult-to-absorb fat-soluble nutrients like vitamin D.

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 and support male and female fertility.  


Article Sources