Medically reviewed by: Dr. Salli Tazuke, a board-certified reproductive endocrinologist and infertility specialist at CCRM Fertility of San Francisco
Vitamin D is known for playing an integral role in bone development by helping your body absorb calcium, but did you know it can also impact your immune system, heart health, digestion, and even your fertility?
Here’s how vitamin D may affect your reproductive health and vitamin D supplementation guidelines to keep in mind if you’re trying to conceive now or in the near future.
What Is Vitamin D?
Vitamin D is a vitamin in the body that helps regulate calcium levels, which keeps your bones, teeth, muscles, and immune system strong. It’s often referred to as the “sunshine vitamin” since you produce vitamin D when your skin is exposed to sunlight, but vitamin D is also found in some foods and supplements.
Normal Vitamin D levels
Typical levels of 25-hydroxy vitamin D, the main storage form of vitamin D, depend on age and typically range from 25–100 ng/ml for adults. About 35% of adults in the United States are deficient in vitamin D, and in a 2019 Reproductive Health study of 500 participants undergoing assisted reproductive technologies (ART) such as in vitro fertilization, only 16% of people had normal levels of vitamin D.
Vitamin D for female fertility
In addition to bone health, vitamin D plays an important role in female reproductive health and hormone production. Sufficient levels of vitamin D have been found to help regulate ovulation and to help prepare the endometrial lining for pregnancy.
A 2024 study found that good vitamin D levels are associated with:
- Improved fertility outcomes
- Higher conception rates
- Successful pregnancy development
Vitamin D status also appears to be especially important for individuals undergoing assisted reproduction. A 2022 study found that women who have adequate levels of vitamin D have more successful outcomes as well as better-quality embryos, highlighting its role in reproductive outcomes.
This tracks with earlier research as well. A six-month study by June L. Fung et al., published in Fertility and Sterility, followed healthy women ages 18–39 with no history of infertility, comparing outcomes between those who met the standard vitamin D requirement and those who didn’t. The results were striking: 67.5% of women with sufficient vitamin D achieved a clinical pregnancy within six months, and 59% went on to have a live birth — compared to just 49% and 40%, respectively, among women with insufficient levels. After adjusting for age, race, BMI, alcohol use, and smoking, women with sufficient vitamin D were 2.26 times as likely to achieve a clinical pregnancy and 2.20 times as likely to have a live birth. It’s worth noting that in this study, women with higher vitamin D levels also had significantly higher intake of iron and folic acid — a factor that could partly account for the improved outcomes.
The evidence for female fertility is compelling, but vitamin D’s role doesn’t stop at conception.
Vitamin D for pregnancy
It’s important to maintain normal levels of vitamin D after conception too. Research from a 2022 study reported that women with low levels of vitamin D more often had the following conditions than women with normal vitamin D levels:
- High blood pressure in pregnancy
- Preeclampsia
- Gestational diabetes
Additionally, a 2025 study concludes that having inadequate levels of vitamin D in the first trimester of pregnancy is more likely to lead to preterm birth. Together, these findings emphasize the importance of sufficient vitamin D throughout pregnancy for both maternal and fetal health.
Vitamin D for male fertility
Vitamin D is important for overall male health, but it can also help maximize male fertility and increase testosterone levels. Research indicates that increasing vitamin D levels can boost testosterone in men, which is crucial for libido, the ability to have an erection, and sperm production.
Lower vitamin D levels in men are associated with poorer semen quality, especially when it comes to sperm motility, according to one 2019 study. Sperm motility is how well sperm can move and travel through the female reproductive tract; better motility means a higher chance of the sperm reaching and fertilizing an egg.
Worth noting: in the Fung et al. study referenced above, the same iron and folic acid correlation seen in women also applied to the men involved in the study — another reason to view diet and supplementation as a package, not a single-nutrient fix.
Vitamin D dosage for fertility
30 ng/ml is the optimal vitamin D blood level for those trying to conceive. If you don’t know your vitamin D level, a doctor can order a simple blood test called the 25-hydroxyvitamin D test.
The International Osteoporosis Foundation recommends that all adults supplement their vitamin D3, and adequate intake is 400 IU per day. If you have deficient levels of vitamin D, you can take higher dosages of vitamin D3 based on the recommendations below:
- If your level is >30 ng/ml: Take 400–800 IU daily
- If your level is between 20–30 ng/ml: Take 1,000 IU daily (available over the counter) and recheck level in 12 weeks
- If your level is ≤20 ng/ml: Take 50,000 IU once a week for 8 weeks (prescribed by a physician), then take 2,000 IU daily (available over the counter) and recheck level in 12 weeks
- If your level is <10 ng/ml: In addition to taking 50,000 IU once a week, you will also need to be seen by an endocrinologist for long-term follow-up care
How to boost Your Vitamin D level
In addition to supplementation, you can naturally boost your vitamin D level by:
- Getting some sunshine: The sun is one of the best sources of vitamin D. Aim to get 5–30 minutes of sunlight twice a week on your skin, longer if you have darker skin. Don’t forget to apply sunscreen!
- Eating seafood and fatty fish: Fish, especially salmon, tuna, oysters, and mackerel, are high in vitamin D.
- Consuming other foods containing vitamin D: Foods that have naturally high levels of vitamin D or have been fortified with it include dairy and plant milk, orange juice, cereal, yogurt, and tofu.
Even with a solid diet, supplementation often matters more than people expect: in the Fung et al. study above, 96% of women who reached the recommended vitamin D level did so with the help of supplements rather than diet alone — so don’t assume food alone will get you there.
Talk to a fertility specialist about your Vitamin D levels
Vitamin D is essential for fertility health, but many of us don’t have the levels we need to optimize reproductive potential. A reproductive endocrinologist can help you assess if you’re getting enough of this important vitamin while you’re trying to conceive and advise you on how to supplement to maximize your chances of success.
To get started with a fertility specialist and learn more about vitamin D and fertility, schedule an appointment with CCRM Fertility.
