Vitamin D might be one of the most impactful supplements for those trying to conceive.

It plays a crucial role in many systems in the body including immune health, bone health, inflammation regulation, glucose metabolism, and insulin sensitivity. No surprise it’s commonly recommended as a supplement!

But wait…didn’t people go for centuries without needing vitamin D supplements?

Yes, they did! But here’s the difference:
We we also used to get more from our food sources and spend more time outside. As a result of our current lifestyle and food availability, sometimes a supplement is necessary to get enough.

Why Vitamin D Matters Even More When You’re TTC

If you’re trying to conceive, there are a few key reasons to be especially mindful of your vitamin D levels:

• Polycystic Ovary Syndrome (PCOS): People with PCOS often have a higher risk of vitamin D deficiency.
• Living in Northern Climates: If you live in a northern latitude, especially during winter, sun exposure (a major source of vitamin D) is limited.
• Plant-Based Diets: Vegans, vegetarians, and pescatarians may not get enough vitamin D through diet alone.

Food Sources of Vitamin D

Even if you’re supplementing, food matters! Include these vitamin D-rich options in your weekly meals:

• Fatty fish (like salmon or mackerel)
• Egg yolks
• Fortified foods (such as milk, orange juice, or cereal)
• UV-treated mushrooms

And don’t forget about sunlight:
Sun exposure, particularly midday sun in the warmer months, helps your skin produce vitamin D naturally through a reaction with UVB rays and a vitamin D precursor found in our bodies.

How Vitamin D Supports Fertility

Here’s what the research suggests about vitamin D and fertility outcomes:

• May improve success rates in IVF (in-vitro fertilization)
• Supports healthy sperm men
• May prevent seasonal declines in anti-Müllerian hormone (AMH)
• Can improve insulin resistance and embryo quality in people with PCOS
• May reduce risk of pregnancy complications, including preeclampsia and gestational diabetes

How Much Vitamin D Should You Take?

A general recommendation is 1,000–2,000 IU per day, but vitamin D needs can vary widely. That’s why I recommend getting your vitamin D levels tested before starting a supplement. Based on your results, you may need a higher (or lower) dose to correct a deficiency.

Can You Take Too Much Vitamin D?

Yes, but it’s rare when taken responsibly.
Vitamin D is a fat-soluble vitamin, which means it’s stored in your body’s fat cells (unlike water-soluble vitamins that are flushed out in urine). Taking very high doses over time can disrupt your body’s vitamin D, calcium, and phosphorus balance.

This is why personalized supplementation matters. Testing first = safer, more effective results.

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Research on the topic: tap here