Vitamin D is a hormone-like vitamin that affects the immune system, hormones, cell maturation and mucous membranes. Vitamin D deficiency is common in the Nordic countries and has been linked in several studies to poorer IVF results and more challenging fertility in general. Therefore, vitamin D is an important piece of the puzzle to check when planning pregnancy or fertility treatment.
It's not about extreme doses, but about avoiding deficiency and aiming for stable, healthy levels.
How does vitamin D affect fertility?
Vitamin D receptors are found in, among other things:
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ovaries
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endometrium
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immune cells
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sex hormone-producing tissue.
Therefore, vitamin D status can affect:
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how egg cells mature
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how the lining receives an embryo
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how the immune system reacts during implantation
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how hormones such as AMH and sex hormones interact.
Women with PCOS often have lower vitamin D levels, and optimizing these is now included in many treatment plans.
What do studies say about vitamin D and IVF outcomes?
Several studies and reviews have shown that:
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Women without vitamin D deficiency often have a better chance of clinical pregnancy during IVF than women with a pronounced deficiency.
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Vitamin D deficiency is overrepresented in certain fertility groups, for example in PCOS or obesity
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Correcting deficiency can improve the overall picture, although vitamin D is not a “quick fix” on its own.
Therefore, vitamin D testing is increasingly included in fertility investigations and IVF preparations.
How long should you take vitamin D before IVF?
Because vitamin D is stored in the body and builds up levels over time, it is wise to think long-term:
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It is advisable to start 6–12 months before IVF if there is a deficiency or risk of deficiency
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aim to have taken vitamin D for at least 3–6 months before egg retrieval
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Combine supplements with regular follow-up via blood tests if necessary.
The important thing is to get to a stable, healthy level – not to take the highest doses possible.
How is vitamin D related to Fay Hepper's approach?
Fay Hepper has integrated vitamin D into their fertility products, especially in the fertility multivitamin. This way, the user gets:
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a basic dose of vitamin D every day
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combined with folate, B vitamins and other key nutrients
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without having to put all the pieces together yourself.
In case of pronounced deficiency, the doctor or midwife can add extra vitamin D on top of this.
Fay Hepper's prenatal The Daily Dose
about vitamin D and fertility
FAQ: Vitamin D and Fertility
Should everyone trying to get pregnant take vitamin D?
Everyone in the Nordic countries is recommended to take vitamin D during parts of the year, and when planning a pregnancy it is especially important to avoid a deficiency. A blood test gives the clearest picture.
Can you take too much vitamin D?
Yes, vitamin D is fat-soluble and can cause side effects in high doses. Therefore, it is important to follow the recommended dose and consult your healthcare provider if you want to take higher doses or have a medical condition.
Is the sun enough?
During the summer months, the sun can cover a large part of the need, but during large parts of the year in the Nordic countries, sunlight is too weak. Therefore, diet and supplements are important sources.