The key idea
The supplement market for fertility is large, and the evidence base behind most of it is thin.
That is not a reason to take nothing.
It is a reason to know which small number of things have real data behind them, take those, and ignore the rest.
That is a harder instruction to follow than it sounds when the products are everywhere.
What Is Worth Knowing
Folate is the one supplement where the evidence is strongest and the recommendation is universal.
The standard UK guidance is 400 micrograms daily, from at least three months before conception and through the first trimester.
5mg is recommended for higher-risk groups: previous neural tube defect, BMI over 30, diabetes, certain medications.
This is about neural tube development, not fertility per se.
But it's the intervention with the clearest evidence and lowest risk.
Vitamin D deficiency is extremely common in the UK.
It is associated with worse IVF outcomes in several cohort studies.
Vitamin D receptors are found in endometrial and ovarian tissue.
The mechanistic plausibility is real, even if the evidence from trials is still building.
The NHS dose is 10 micrograms (400 IU) daily, at least October to March.
If you've never checked your level, that's worth doing once.
Most people in northern latitudes are deficient at some point each year, regardless of diet.
CoQ10 is involved in mitochondrial energy production.
Eggs are among the most mitochondria-dependent cells in the body.
Mitochondrial function in eggs does decline with age.
Some small trials suggest supplementation may improve markers of egg quality and embryo development, mainly in women over 35 or with low ovarian reserve.
There is only limited, small-study evidence and no large trial.
Small studies in men suggest it may help sperm movement and shape. Ask your GP or clinic before adding it.
Omega-3 fatty acids affect membrane composition in eggs and sperm.
The UK diet is generally deficient in EPA and DHA.
The fertility-specific evidence is reasonable but not strong.
The case for supplementation is better in pregnancy: preterm birth risk, fetal neurodevelopment.
Ask your GP or clinic before adding it. It can come from a quality fish oil or an algae-based equivalent.
The Short List, and Where to Stop
Folic acid 400 micrograms daily (5 mg if your GP says you're higher risk), from 3 months before trying until 12 weeks.
Vitamin D 10 micrograms (400 IU) daily, at least October to March. NHS guidance stops there.
CoQ10 and omega-3 have only limited, small-study evidence: ask your GP or clinic before adding them.
Everything else requires a specific reason: a deficiency, a diagnosis, a clinical recommendation.
Whether a prenatal multi-vitamin is useful depends on your starting point.
If you are vegan or vegetarian, a multi that includes B12 and iodine closes a gap that diet alone often doesn't.
Both matter in early pregnancy. Neither is reliably covered by plant-based eating.
You may have a history of heavy periods, or never have had your ferritin checked.
If so, iron is worth testing before supplementing rather than assuming.
High-dose iron without a confirmed deficiency adds no benefit and can cause symptoms.
Outside these groups, folic acid and vitamin D cover what NHS guidance recommends.
If you're unsure where you land, that's exactly the question to take to your GP.
When a product makes a claim, the question to ask is 'what is the trial that shows this', rather than 'does this sound plausible'.
An information resource, not a medical device and not SaMD.
CSO safety framework completed.
Clinical decisions rest with the treating clinician.