Fertility Nutrition After 12 Months Trying

Fertility Health Guides and Reproductive Health Research Fertility Nutrition After 12 Months Trying
Evidence-based fertility nutrition guide for couples who have been trying to conceive for 12 months or longer

Twelve months of trying without a pregnancy is the clinical threshold that defines infertility under the current NICE fertility guideline (NG257, published March 2026) and the ESHRE 2023 guideline on unexplained infertility.1,2 It is also the point at which most UK couples are offered a formal investigation — and a waiting list of several months is common before any active treatment begins.

That gap between reaching the 12-month mark and the first clinical intervention is when a well-designed nutrition protocol matters most. The final phase of egg development takes approximately 85–90 days, and sperm complete their development cycle in approximately 72–74 days.3,4 So any supplement you start today primarily influences the gametes that will be ovulated or ejaculated around three months from now.

This article sets out what the evidence does and does not support for couples at this stage. Each recommendation is graded by the strength of the underlying research, separated by partner, and mapped to the three phases most couples pass through: active investigation, assisted conception, and IVF where relevant. None of this replaces personalised clinical advice — before starting any new supplement, particularly if you take prescription medication, discuss it with your GP or fertility clinician.

Key takeaways

  • After 12 months, both partners should have a simultaneous nutrition plan — not just the woman.
  • Supplement protocols need a 3-month minimum because gametes develop over ~85–90 days (eggs) and ~72–74 days (sperm).
  • Consistent but low-to-moderate certainty evidence supports a combined-antioxidant approach (CoQ10, vitamin E, selenium, zinc) for both partners.
  • Folate — in either folic acid or methylfolate form — and vitamin D sufficiency are foundational priorities for women planning conception.
  • Evidence strength is graded throughout: “strong”, “moderate”, or “preliminary”.
  • Nutrition is complementary to clinical treatment — it is not a substitute for investigating tubal, ovulatory, or male-factor causes.

What does the 12-month milestone actually mean?

Reaching 12 months of unprotected intercourse without conception places a couple under the WHO definition of infertility, regardless of whether a specific cause has been identified.1 Roughly one in seven UK couples meets this definition, and the most common outcome of initial investigation is “unexplained” infertility — meaning semen analysis, tubal patency, and ovulatory testing all return normal results.2

At this point the clinical pathway typically moves from watchful waiting to active investigation:

  • Semen analysis for the male partner
  • Mid-luteal progesterone to confirm ovulation
  • AMH or antral follicle count for ovarian reserve
  • Tubal patency test (HSG or HyCoSy) for the female partner

The NHS funded pathway varies by local Integrated Care Board but usually requires 12 months of trying before IUI or IVF referral is considered. While you wait, you have a narrow window in which nutrition can meaningfully influence the gametes that will eventually be used — whether naturally conceived or retrieved for IVF.

Why does the 90-day biology lesson matter for supplement timing?

A mature ovulated egg spent its final ~85–90 days progressing through antral follicle development, during which it is highly sensitive to oxidative stress and mitochondrial energy status.3 Sperm complete their development cycle in approximately 72–74 days, with an additional 2–10 days of epididymal transit.4

The practical implication is straightforward: a supplement started today is not influencing next week’s ovulation or next week’s ejaculate. It is influencing the egg you will ovulate in about three months and the sperm that will be ejaculated in about ten weeks.

For any supplement protocol to have a fair chance of showing a benefit, it needs a minimum of three months of consistent daily intake before the first cycle in which its effect could appear. Starting a protocol in the same month as an IUI cycle gives you almost none of the biological effect you are hoping for. This is why fertility clinicians increasingly recommend beginning targeted nutritional support 3 to 6 months before any planned treatment cycle.

What should a woman’s advanced nutrition protocol include at this stage?

The 2020 Cochrane review of antioxidant supplementation in women with subfertility (63 randomised trials, 7,760 women) concluded that antioxidants may be associated with increased clinical pregnancy rates compared with placebo, though the overall certainty of evidence was rated low.5 The most consistently studied compounds were CoQ10, N-acetylcysteine, melatonin, myo-inositol, and combinations of vitamins C and E with selenium.

Before starting any of these, discuss the plan with your GP or fertility clinician, particularly if you are already taking prescription medication.

CoQ10. This has accumulated some of the strongest single-compound evidence. A 2024 meta-analysis of six RCTs in women with diminished ovarian reserve undergoing IVF found that CoQ10 pretreatment (200–600 mg/day over 60–90 days) was associated with improved oocyte quality indicators and higher clinical pregnancy rates.6 A starting dose of 200 mg/day is reasonable for general preconception use; if diminished ovarian reserve is confirmed, discuss the higher trial doses (up to 600 mg/day) with your fertility clinician.

Myo-inositol. At 2–4 g/day, myo-inositol has a meaningful evidence base in women with PCOS, where meta-analyses have shown improvements in insulin sensitivity, fasting insulin, and androgen markers.7 It is worth noting that the combined evidence base overlaps substantially with studies authored by researchers affiliated with inositol manufacturers, which readers should weigh. If you are already taking metformin for PCOS, discuss myo-inositol with your GP or fertility clinician first — the two agents have overlapping insulin-sensitising mechanisms and your metformin dose may need adjustment.

Folate. At 400–800 µg/day (as folic acid or methylfolate), folate is essential for women planning conception. The MTHFR C677T variant reduces enzyme activity by approximately 35% (heterozygous) or 70% (homozygous), but routine MTHFR genotyping is not recommended by ACMG, ACOG, or current UK preconception guidance for the general population.8 Methylfolate (the active, already-methylated form) is a reasonable, low-risk choice for women with known C677T status, and is increasingly the default in preconception products. The standard 400 µg/day NHS-recommended folic acid dose remains the cornerstone for routine preconception care.

Vitamin D. Vitamin D status is associated with assisted-reproduction outcomes in observational data: the Chu 2018 meta-analysis found higher clinical pregnancy and live birth rates in women classified as “replete” (>75 nmol/L) versus deficient/insufficient.9 Current UK SACN and NHS guidance treats serum 25(OH)D above 50 nmol/L as sufficient; above that, values are best interpreted with clinician input rather than targeted in isolation.

Omega-3. EPA/DHA at 1–2 g/day is supported by observational and some trial data, including a 2022 prospective cohort study of 900 women that found omega-3 supplement use was associated with a 1.51-fold increase in the probability of conceiving (95% CI 1.12–2.04), with the usual caveat that omega-3 users tend to be healthier overall.10

A well-constructed protocol for women at this stage therefore combines folate (folic acid or methylfolate), vitamin D, CoQ10, omega-3, and a broad-spectrum antioxidant base (vitamin E, vitamin C, zinc, selenium). This is the logic behind choosing a fertility-specific formulation built around the 3-month gamete-development window rather than a generic prenatal vitamin.

What should a man’s advanced nutrition protocol include at this stage?

A male factor is a primary or contributing cause in approximately 50% of couple infertility cases.11 The 2022 Cochrane review of antioxidants for male subfertility (90 trials, 10,303 men) concluded that antioxidants probably increase live birth and clinical pregnancy rates compared with placebo, with evidence certainty rated low-to-moderate.12

The best-studied individual compounds are:

  • L-carnitine (2–3 g/day): improved sperm motility in a 2021 meta-analysis of seven RCTs (621 men)13
  • CoQ10 (200–400 mg/day): consistent improvements in sperm concentration and motility across trials in a 2021 systematic review14
  • Zinc (15–30 mg/day): required for spermatogenesis; deficiency is associated with reduced sperm count
  • Selenium (100–200 µg/day): supports sperm structural integrity
  • Vitamin E (100–400 IU/day) combined with vitamin C: reduces sperm DNA fragmentation

The 2022 Cochrane update reported that combination antioxidant regimens showed effects on clinical pregnancy and live birth rates comparable to — and in several comparisons larger than — single-compound regimens. This is consistent with the rationale for multi-ingredient male formulations over isolated high-dose single ingredients.12

Men should also address modifiable lifestyle factors alongside supplementation: scrotal heat exposure (laptops on laps, hot baths), tobacco, and heavy alcohol use all independently impair sperm parameters and will blunt any supplement benefit.

How does nutrition integrate with active clinical treatment?

Most targeted fertility nutrients are safe to continue during IUI and IVF cycles, but there are three scenarios in which your fertility clinic may ask you to pause or adjust:

  • High-dose vitamin E (above 400 IU/day) and fish oil in therapeutic doses may increase bleeding time and are sometimes paused for 7–10 days around egg retrieval.
  • High-dose vitamin C (above 2 g/day) has theoretical interactions with some ovarian stimulation protocols and is usually not needed at those doses anyway.
  • Melatonin at 3 mg/night should be discussed with the clinic because some protocols use or avoid it depending on the stimulation regimen.

No reputable clinic will ask you to stop folate, vitamin D, CoQ10 at standard fertility doses, zinc, or selenium. Continue them through the cycle. Bring a written list of everything you are taking, with doses, to your first consultation and again before any IVF stimulation begins.

Safety notes

  • Selenium has a narrow therapeutic-to-toxic margin. UK NHS guidance is that supplemental intakes above 350 µg/day are best avoided, and the EFSA 2023 opinion sets a tolerable upper intake of 255 µg/day from all sources combined. Avoid stacking multiple selenium-containing supplements beyond a combined 200 µg/day without clinician supervision.
  • Preformed vitamin A (retinyl palmitate / retinol) supplements above 3,000 µg RAE/day (10,000 IU/day) should be avoided while trying to conceive, because preformed vitamin A is teratogenic at high doses. Beta-carotene and mixed-carotenoid sources do not carry the same concern.
  • CoQ10 and warfarin: if you are taking warfarin or another anticoagulant, discuss CoQ10 with your prescriber — it has a theoretical interaction with warfarin, and dose timing may need review.

What does a phase-based protocol look like in practice?

The table below maps the protocol across three phases most couples encounter between month 12 and the first treatment cycle. Evidence strength refers to the weight of RCT and meta-analytic data supporting each recommendation.

Phase Woman Man Evidence
Months 13–15
Active investigation		 Folate 400–800 µg, vitamin D 1,000–2,000 IU, CoQ10 200 mg, omega-3 1 g EPA+DHA, broad antioxidant base (zinc, selenium, vitamins C and E) L-carnitine 2 g, CoQ10 200 mg, zinc 25 mg, selenium 100 µg, vitamin E 100 IU, vitamin C 500 mg Strong (combined), moderate (single compounds)
Months 16–18
IUI or expectant management		 Continue as above. Consider myo-inositol 4 g if PCOS features present. Continue as above. Consider raising CoQ10 to 300–400 mg if DNA fragmentation flagged. Moderate
Parallel to IVF
Stimulation and retrieval		 Continue folate, vitamin D, CoQ10. Pause high-dose vitamin E (>400 IU) and fish oil 7–10 days pre-retrieval if clinic advises. Continue full protocol; no clinic pause required in most cases. Strong (safety), moderate (IVF efficacy)

Evidence-strength key:

  • Strong: multiple RCTs and at least one meta-analysis consistently showing benefit, with plausible mechanism and low safety concern.
  • Moderate: several positive trials with some mixed results, or one large meta-analysis with low-to-moderate certainty.
  • Preliminary: small trials, observational data, or indirect biological rationale only.

How should you grade the evidence behind each supplement?

Not every recommendation in the protocol above carries equal weight. Understanding the grading helps you avoid over-relying on a single headline finding and interpret the conflicting results you may encounter online.

  • Folate: Strong. The evidence for periconceptional folate in preventing neural-tube defects is extensive and replicated.
  • Vitamin D: Strong-to-moderate. Meta-analytic evidence is consistent for the association with ART outcomes, but RCT evidence on supplementation is less consistent, and the causal direction is debated.
  • CoQ10 (both partners): Strong-to-moderate. The mitochondrial mechanism is robust and clinical trial results are mostly positive, but sample sizes are smaller than ideal.
  • Combined antioxidant therapy (both partners): Moderate. Meta-analyses consistently show benefit but rate evidence certainty as low-to-moderate due to heterogeneity in trial designs.
  • Myo-inositol for PCOS: Strong within that population, with the conflict-of-interest caveat noted above.
  • L-carnitine in men: Moderate.
  • Omega-3 (both partners): Moderate.
  • Melatonin and NAC in women: Preliminary-to-moderate — discuss with a clinician.

When should you escalate from nutrition to clinical intervention?

Nutrition is not a replacement for investigation. After 12 months, both partners should have had a full workup — semen analysis, ovulation confirmation, ovarian reserve markers, and tubal assessment — regardless of what supplement protocol is in place.

If any investigation returns an abnormal result (such as tubal blockage, severe male factor, anovulation, or low AMH for age), nutrition becomes a complement to a specific clinical plan, not a delaying tactic.

Current UK guidance (NICE NG257, 2026) recommends specialist referral after 12 months of unsuccessful trying for women under 36, with earlier referral (after 6 months) considered for women aged 36 and over or where a clinical factor is already suspected. NHS-funded IVF eligibility for couples with unexplained infertility typically follows a further period of trying and varies by local Integrated Care Board. Your GP can explain the specific pathway in your area.1

If you have been trying for 18 months with a normal workup, if you are over 35, or if either partner has abnormal results, escalation to IUI or IVF should not be deferred to “give the supplements more time.” The ~90-day biology still applies — but it applies alongside, not instead of, the clinical pathway.

What mistakes do couples typically make at this stage?

Four errors recur across UK fertility forums and clinic conversations:

  1. The man does not supplement. Both gametes contribute to embryo quality, and male-factor oxidative stress can impair outcomes even when standard semen analysis is normal.
  2. Couples switch products repeatedly, never giving any protocol the 90 days it needs to show an effect.
  3. Doses fall below therapeutic thresholds. A multivitamin containing 50 mg CoQ10 is not delivering the dose that has been studied in fertility trials.
  4. Couples stop supplements without discussing it with their fertility clinic, often because they were told to “bring a list” and interpreted this as “stop everything.”

Avoiding these errors is simple: both partners start together, stay on a single protocol for three months, choose products that disclose therapeutic doses, and bring a written list to every clinic appointment rather than guessing what is allowed.

Frequently asked questions

How long should we take fertility supplements before IUI?

The minimum useful window is three months, because eggs develop over ~85–90 days and sperm over ~72–74 days. Most fertility clinicians recommend beginning targeted supplementation 3 to 6 months before the first planned IUI cycle. Supplements started in the same month as the cycle influence the cycle after next, not the current one.

Can I take fertility supplements during IVF stimulation?

Most are safe to continue. Folate, vitamin D, CoQ10 at standard doses, zinc, and selenium are routinely continued. High-dose vitamin E (above 400 IU/day) and high-dose fish oil may be paused 7–10 days before egg retrieval at some clinics because of theoretical bleeding-time effects. Bring a written list of everything you take to your first clinic appointment.

Is CoQ10 safe for both partners?

Yes. CoQ10 at 100–600 mg/day has been used in female and male fertility trials over 60- to 90-day periods with a consistent safety record. It is not hormonal and does not interact with standard fertility medications. Ubiquinol is the active form and may be preferred in adults over 40 due to slightly better absorption, although the evidence base in fertility trials predominantly used ubiquinone. If you are taking warfarin or another anticoagulant, discuss it with your clinician.

Do I need to stop fertility supplements if I get pregnant?

You should transition from a fertility-specific supplement to a pregnancy-appropriate prenatal vitamin as soon as a positive test is confirmed. Core nutrients — folate, vitamin D, iodine, choline — continue throughout pregnancy. High-dose fertility-specific compounds (L-carnitine, myo-inositol beyond PCOS management) are typically stopped once pregnancy is established.

Can antioxidant supplements replace IVF?

No. Nutrition supports gamete quality but cannot bypass a blocked tube, resolve a severe sperm count, or restart a non-ovulatory cycle. For couples with identifiable causes, supplementation complements treatment but does not replace it. The evidence that supports supplements as helpful is meta-analytic evidence on live birth rates alongside standard care, not in place of it.

What if only one partner will take supplements?

It is better than nothing, but the couple evidence is stronger than the single-partner evidence. Meta-analyses note that the largest effect sizes for couple outcomes were in trials where both partners were supplementing.12 Where possible, supplement together.

How much does an advanced fertility nutrition protocol cost per month?

A well-designed dual-partner protocol from a single reputable supplier typically costs £40–£70 per month per person. Assembling the same dose profile from multiple single-ingredient products often costs more and reduces adherence.

Supporting Your Fertility with FertilitySmart

A well-designed protocol built around the evidence above is what “advanced fertility nutrition” should mean in practice — therapeutic doses, bioavailable forms, mechanism coverage for both partners, and honest evidence-based formulation.

If you are at the 12-month mark and looking for a single starting point for both partners, explore our advanced fertility nutrition range for women and men, formulated to deliver the combined-antioxidant and active-form support discussed in this article. You can also explore FertilitySmart’s fertility supplements for men if you want to understand the specific formulation used in male-factor support.

For a wider orientation to the category, see the complete guide to fertility supplements for women and men, which sets out the full framework for choosing supplements across the conception journey. To go deeper on how the “advanced” framework is built around the evidence above, see what makes a fertility supplement advanced.

References

  1. National Institute for Health and Care Excellence. Fertility problems: assessment and treatment. NICE guideline NG257. London: NICE; published 31 March 2026 (replaces CG156). https://www.nice.org.uk/guidance/ng257
  2. Romualdi D, Ata B, Bhattacharya S, et al; ESHRE Guideline Group on Unexplained Infertility. Evidence-based guideline: unexplained infertility. Hum Reprod. 2023;38(10):1881-1890. doi:10.1093/humrep/dead150
  3. Gougeon A. Human ovarian follicular development: from activation of resting follicles to preovulatory maturation. Ann Endocrinol (Paris). 2010;71(3):132-143. doi:10.1016/j.ando.2010.02.021
  4. Amann RP. The cycle of the seminiferous epithelium in humans: a need to revisit? J Androl. 2008;29(5):469-487. doi:10.2164/jandrol.107.004655
  5. Showell MG, Mackenzie-Proctor R, Jordan V, Hart RJ. Antioxidants for female subfertility. Cochrane Database Syst Rev. 2020;8(8):CD007807. doi:10.1002/14651858.CD007807.pub4. (Editorial note dated 5 March 2026 flagging 9 of 63 included trials — 7 retractions, 2 expressions of concern; editors confirm pooled findings are not meaningfully impacted.)
  6. Lin G, Li X, Yie SLJ, Xu L. Clinical evidence of coenzyme Q10 pretreatment for women with diminished ovarian reserve undergoing IVF/ICSI: a systematic review and meta-analysis. Ann Med. 2024;56(1):2389469. doi:10.1080/07853890.2024.2389469
  7. Unfer V, Facchinetti F, Orrù B, Giordani B, Nestler J. Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials. Endocr Connect. 2017;6(8):647-658. doi:10.1530/EC-17-0243 (Authors include researchers affiliated with inositol manufacturers; readers should weigh this COI; corroborated for metabolic markers by independent reviews including the 2023/2024 update of the International Evidence-based PCOS Guideline.)
  8. Frosst P, Blom HJ, Milos R, et al. A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase. Nat Genet. 1995;10(1):111-113. doi:10.1038/ng0595-111
  9. Chu J, Gallos I, Tobias A, Tan B, Eapen A, Coomarasamy A. Vitamin D and assisted reproductive treatment outcome: a systematic review and meta-analysis. Hum Reprod. 2018;33(1):65-80. doi:10.1093/humrep/dex326
  10. Stanhiser J, Jukic AMZ, McConnaughey DR, Steiner AZ. Omega-3 fatty acid supplementation and fecundability. Hum Reprod. 2022;37(5):1037-1046. doi:10.1093/humrep/deac027
  11. Agarwal A, Baskaran S, Parekh N, et al. Male infertility. Lancet. 2021;397(10271):319-333. doi:10.1016/S0140-6736(20)32667-2
  12. de Ligny W, Smits RM, Mackenzie-Proctor R, Jordan V, Fleischer K, de Bruin JP, Showell MG. Antioxidants for male subfertility. Cochrane Database Syst Rev. 2022;5(5):CD007411. doi:10.1002/14651858.CD007411.pub5
  13. Wei G, Zhou Z, Cui Y, et al. A meta-analysis of the efficacy of L-carnitine/L-acetyl-carnitine or N-acetyl-cysteine in men with idiopathic asthenozoospermia. Am J Mens Health. 2021;15(2):15579883211011371. doi:10.1177/15579883211011371
  14. Salvio G, Cutini M, Ciarloni A, Giovannini L, Perrone M, Balercia G. Coenzyme Q10 and male infertility: a systematic review. Antioxidants (Basel). 2021;10(6):874. doi:10.3390/antiox10060874

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Marina Carter, Fertility Health Expert

Marina Carter

Health & Fertility Writer at FertilitySmart

Marina Carter is a specialist health writer with nearly a decade of experience in reproductive health, fertility nutrition, and evidence-based conception support. She has authored over 30 in-depth articles for FertilitySmart, translating peer-reviewed research into clear, practical guidance for individuals and couples on their fertility journey. Read full bio →

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