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    Vitamin D, fertility, and the South Asian gap

    Reviewed by HHH Clinical Team · April 2026

    1 section · 2 min read

    Food & Supplements
    2 minHHH clinical team
    WHY IS VITAMIN D IMPORTANT BEFORE FERTILITY TREATMENT?

    Why is vitamin D important before fertility treatment?

    Vitamin D status sits in a quiet but important place in fertility care. It is rarely a single cause of difficulty conceiving. It interacts with several systems that fertility care touches: insulin signalling in PMOS, menstrual regularity, levels, and cycle outcomes in some studies. The evidence is mixed, the standard supplementation dose may not be enough for South Asian women in northern climates, and the lab range labelled 'normal' was not designed with fertility in mind.

    This article walks through what UK NICE, US ACOG, and the international guideline say, where the South Asian evidence diverges, and what a useful conversation with your doctor might look like. We do not tell you what to take. We give you the picture so you can have that conversation properly.

    The grey zone

    How much vitamin D should I take?

    Standard position · UK

    UK NICE recommends 10 micrograms (400 IU) daily for all adults during autumn and winter, and year-round for those with darker skin or limited sun exposure. The Department of Health treats this as a bone-health and general-health figure, not a fertility figure.

    Where it gets more nuanced

    What we honestly do not know

    We do not know whether higher doses change live birth rate. We do not have randomised trial data settling the optimal target level for IVF preparation. We do not know how much of the South Asian fertility gap, if any, is mediated by vitamin D status. The mechanistic plausibility is good. The interventional evidence is weaker than the prevalence data.

    Bottom line

    Testing your vitamin D level will give you and your doctor real information. The standard dose may not be enough for you specifically. There is genuine uncertainty about what 'optimal' looks like for fertility. This is a conversation worth having with someone who knows your context.

    References

    1. [1] nice-ng56-vit-d-2026NICE Public Health Guideline PH56: Vitamin D: supplement use in specific population groups.
    2. [2] 22640517Darling AL et al. Vitamin D status in UK South Asian populations. Br J Nutr 2013.
    3. [3] 29149263Chu J et al. Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Hum Reprod 2018;33(1):65-80.
    4. [4] 37580927Teede HJ et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023.

    Browse the full evidence library →

    For your doctor

    Patient is preparing for fertility assessment / treatment. Requests serum 25(OH)D measurement and review of replete status target rather than population reference range, in context of South Asian ethnicity and northern hemisphere residence. Ref: NICE PH56, ESHRE PCOS 2023.

    I would like a vitamin D test, please. I am preparing for fertility care. Given that I am South Asian and live here, I would like to know whether my level is replete for fertility, not just within the lab range. Could we look at the actual number?

    How did this land with you?

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    References

    1. [1] nice-ng56-vit-d-2026NICE Public Health Guideline PH56: Vitamin D: supplement use in specific population groups.
    2. [2] 22640517Darling AL et al. Vitamin D status in UK South Asian populations. Br J Nutr 2013.
    3. [3] 29149263Chu J et al. Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Hum Reprod 2018;33(1):65-80.
    4. [4] acog-prenatal-vit-d-2024ACOG Committee Opinion: Vitamin D screening and supplementation during pregnancy.
    5. [5] 37580927Teede HJ et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023.

    Browse the full evidence library →

    Reviewed by clinicians

    Authored and reviewed by clinicians from the founding team. Information only, not personalised medical advice.