The Role of Vitamin D in Fertility

Vitamin D gets a lot of attention in fertility circles, and for good reason: it’s involved in many processes in the body, and low levels are common. But the research on vitamin D and fertility is more complicated than many headlines suggest. If you’ve been overwhelmed by conflicting information, you’re not alone. This guide sorts through what’s known, what’s still uncertain, and how to talk to your doctor about your levels.

This article is for education and support only and is not medical advice. Please talk with your doctor or fertility specialist about your own situation. As an Amazon Associate, Fertility Mommies earns from qualifying purchases, at no extra cost to you.

What vitamin D does in the body

Vitamin D is best known for helping the body absorb calcium and keep bones strong. But it acts more like a hormone than a typical vitamin, and receptors for it are found in many tissues, including the ovaries, uterus, placenta, and testes. That’s one reason researchers are interested in its possible role in reproduction.

Your body makes vitamin D when your skin is exposed to sunlight. You can also get it from certain foods and supplements.

What the research says about vitamin D and fertility

For women

Several observational studies have found links between low vitamin D levels and certain reproductive outcomes, including some IVF outcomes. Other studies haven’t found a clear connection. Observational studies can show associations, but they can’t prove that low vitamin D causes a problem. People with low vitamin D may differ in other ways too, like overall health or diet.

Studies testing whether vitamin D supplements improve pregnancy rates have had mixed results so far. Researchers are still working to understand who, if anyone, benefits most.

For people with PCOS

Vitamin D has been studied in PCOS, where low levels seem common. Some research suggests it may play a role in insulin sensitivity and ovulation, but the evidence isn’t strong enough to call it a treatment. Learn more about PCOS and fertility.

For men

Some studies have looked at vitamin D and sperm quality, particularly motility. The findings are interesting but not conclusive. Our guide to sperm health and what men can do covers habits with more support.

During pregnancy

Vitamin D is important for bone development in the baby. Prenatal vitamins usually include some vitamin D, and your doctor may recommend more if your levels are low.

Who’s more likely to have low vitamin D?

Vitamin D deficiency is common. You may be more likely to have low levels if you:

• Live in a northern climate or spend little time outdoors
• Have darker skin, which makes less vitamin D from the same sun exposure
• Regularly use sunscreen or cover most of your skin outdoors
• Have a higher body weight
• Have conditions that affect fat absorption, like celiac or inflammatory bowel disease
• Follow a diet low in vitamin D sources

How to check your vitamin D level

Vitamin D is measured with a simple blood test, usually called 25-hydroxy vitamin D. Many fertility clinics check it as part of preconception or IVF testing, but not all do. If you’re curious, ask your doctor whether testing makes sense for you. Our guide to what your fertility blood work means explains other common tests.

Ways to get enough vitamin D

Sunlight

Short periods of sun exposure can help your body make vitamin D, but the amount varies a lot depending on where you live, the season, and your skin tone. Balance this with skin cancer prevention.

Food sources

Only a few foods are naturally rich in vitamin D:

• Fatty fish like salmon, trout, and sardines
• Egg yolks
• Fortified foods like milk, some plant-based milks, cereals, and orange juice
• Some mushrooms exposed to UV light

For fish ideas that are also lower in mercury, try our omega-3 rich recipes for fertility.

Supplements

Many prenatal vitamins include vitamin D. If your doctor finds that your levels are low, they may recommend a separate vitamin D3 supplement and tell you how much to take. Don’t take high doses on your own. Vitamin D is fat-soluble, which means it can build up in the body, and too much can be harmful.

Questions to ask your doctor

• Should my vitamin D level be checked?
• If it’s low, what do you recommend, and for how long?
• When should I recheck my levels?
• Does my prenatal vitamin contain enough, or do I need more?
• Should my partner have their level checked too?

Frequently asked questions

Can low vitamin D cause infertility?

There’s no clear evidence that low vitamin D alone causes infertility. Some studies show associations with certain outcomes, but research hasn’t proven cause and effect.

Should I take vitamin D before IVF?

Ask your doctor. Some clinics test and treat low levels before IVF, especially since correcting a deficiency is good for overall health.

Can you take too much vitamin D?

Yes. Very high doses can cause high calcium levels and other problems. Stick to the amount your doctor recommends.

The bottom line

Vitamin D matters for your overall health, and low levels are common. The research on vitamin D and fertility is still evolving, and supplements aren’t a proven fertility fix. The best next step is to ask your doctor about testing and follow their guidance if your levels are low. Share this with someone who’s been wondering about vitamin D on their TTC journey.