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Should you take vitamin D when trying to conceive?

Should you take vitamin D when trying to conceive?

Nicole Knight, AHCJ | May 29, 2020 | Getting Pregnant

Vitamin D is called the sunshine vitamin because you can reap its benefits by soaking up just a few minutes of sun each week. Despite how easy it is to get a healthy dose of this vitamin, up to half of women of child-bearing age are deficient. Many of us are shortchanging our bodies — and fertility — of this essential vitamin (1, 2). 

If you’re curious about taking vitamin D when trying to get pregnant, we’re here to help. Read on for evidence-based answers on the role of this vitamin in conception and pregnancy, and the low-down on whether standard prenatal vitamins contain enough vitamin D.

What is vitamin D?

Vitamin D is essential for strong bones but also takes on other roles. It comes in two forms: D2 and D3. D2, called ergocalciferol, is found in most multivitamins. D3, or cholecalciferol, is produced by your skin when you’re basking in the sun. Fortified cereals, fish liver oils, and egg yolks all contain this form of vitamin D (3).

Is a lack of vitamin D bad for my reproductive health?

Vitamin D deficiency may make it harder to conceive and have a healthy pregnancy. Getting too little of this vitamin is also linked to conditions that affect fertility, including polycystic ovary syndrome (PCOS), endometriosis, and uterine fibroids (2).

A lack of vitamin D in pregnancy can increase the risk of pregnancy complications like gestational diabetes and preterm birth. The deficiency can pass to newborns, making them more susceptible to broken bones as babies (1, 2). 

Who has low vitamin D?

Nearly anyone can be low in vitamin D. The deficiency is so widespread in women that many fertility clinics routinely screen for it and recommend supplements to those who need the vitamin (4).

According to the American College of Obstetricians and Gynecologists (ACOG), certain groups are at greater risk of vitamin D deficiency in pregnancy. This includes vegetarians, people who largely stay indoors or live in sunless climates, and individuals with darker skin (5).

Should I take vitamin D if I'm trying to get pregnant?

Until recently, research was mixed on whether vitamin D was a fertility boon or bust. But a 2020 paper out of Denmark offers strong evidence that vitamin D may provide a fertility advantage (2). 

As part of a national health campaign, Denmark required all margarine sold in the country to be fortified with around 50 IU of vitamin D for more than two decades. When researchers studied the effect of the fortified margarine program on fertility, they found that women diagnosed with infertility during the program had an 87% higher chance of having a live birth within a year of their diagnosis than women diagnosed with infertility after the program ended (2). 

The bottom line? Vitamin D somehow caused a spike in fertility in previously infertile women. Even when researchers accounted for factors like sun exposure and age, the findings remained statistically significant (2). 

How does vitamin D affect fertility?

Vitamin D seems to influence fertility through several avenues, although the exact mechanisms are still under investigation. Scientists have found vitamin D receptors (signaling cells) in endometrial tissue, and theorize the vitamin may help prep the endometrium for pregnancy and possibly play a role in implantation (2). 

In addition, there is some research showing that vitamin D may have a direct effect on AMH production. Vitamin D  seems to help trigger the production of anti-Müllerian hormone (AMH), a marker of ovarian reserve, which is the number of eggs in your ovaries (2). Due to this increase in AMH correlation with vitamin D, there is a  hypothesis that healthy levels of vitamin D may help women  maintain their ovarian reserve for longer (12). This hypothesis, however, has not been proven yet. 

(If you’re curious about at-home tests of AMH and other fertility markers, this post covers the pros and cons.)

Science also shows that vitamin D may play a role in fertility by helping to regulate circadian rhythm. Although you may already know about circadian rhythm’s effect on your sleep-wake cycle, you may not realize the rhythm correlates with the phases of the menstrual cycle. Just as your menstrual cycle follows a pattern, so does your circadian rhythm (6, 7).


Continuous core body temperature, which can identify circadian rhythm patterns, is emerging as the gold-standard method to tell when you’re most fertile (8, 9). To learn more about how to maximize your chances of getting pregnant, click the button below:

Learn About The Priya Fertility System


Can too much vitamin D be toxic?

Going overboard on vitamin D can be toxic in rare instances. It can lead to a harmful condition where calcium builds up in your blood and leaves deposits in your arteries and other tissues. An excess of D also may make you more prone to getting kidney stones (11).

How much vitamin D should I take when trying to conceive?

At the moment, there are no good answers for the right amount of vitamin D to take to boost your fertility. The science is still too new for major medical groups to have issued recommendations like they have done with vitamin D and pregnancy.

Most prenatal vitamins contain 400 IU of vitamin D. If you become pregnant, and you're low in vitamin D, ACOG advises a daily dose of 1,000-2,000 IU. Some doctors, however, suggest doses as high as 4,000 IU daily to cure a deficiency. This may be because one recent study found that a daily dose of 4,000 IU of vitamin D was most effective to avoid pregnancy complications like premature labor and preterm birth (1, 4, 5).

The bottom line? Vitamin D is an essential vitamin and can be incredibly beneficial, but while rare, also can be toxic if you have too much (13). As with all supplements, whether you’re TTC or already pregnant, talk to your provider first before upping your intake of vitamin D.  

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