Start with what is actually recommended

Two supplements appear in UK preconception advice, and neither is sold on the promise you are being offered.

Folic acid

The NHS advises taking folic acid while trying for a baby and through the early weeks of pregnancy. What it does is reduce the risk of neural tube defects — problems in the development of the brain and spine. It does not improve your chance of conceiving, and it is not a fertility supplement. It matters because it works in the first weeks of pregnancy, often before you know you are pregnant, which is why it belongs in the preconception period rather than the antenatal one.

Standard advice differs by risk group. A higher, prescription-strength dose is recommended for some people — including those with diabetes, certain blood conditions, a personal or family history of neural tube defects, and those taking certain medicines. NICE guideline NG3, for example, recommends a higher-dose prescription for people with diabetes planning a pregnancy. If you might be in one of these groups, ask your GP; the higher dose is a prescription, not a product on a shelf, and the standard supermarket item is not equivalent.

Vitamin D

The NHS advises considering a daily vitamin D supplement during autumn and winter, and all year for people at higher risk of deficiency. This is general adult health advice, not fertility advice.

Everything else is a longer conversation.

What the guidance says about the rest

NICE's positions in this area are unusually direct, and they are not what supplement marketing implies.

Sperm DNA integrity: NICE recommends not offering supplements, antioxidants or medical treatments to improve sperm DNA integrity. That is a recommendation against, not an absence of a recommendation.
Androgens: NICE recommends not offering androgens to treat semen abnormalities. Androgen supplementation is also on the HFEA's rated add-ons list, where it holds a grey rating meaning effectiveness cannot be assessed for want of good evidence.
Complementary therapies: NICE states that complementary therapies have not been properly evaluated for fertility problems.
Caffeine: NICE states there is no consistent evidence of an association between caffeinated drinks and fertility problems — relevant because "fertility teas" are often sold as caffeine replacements on a premise that is not established.

The HFEA's position on antioxidants and vitamins in male fertility is the most generous statement available from a UK body, and it is still hedged: there is some evidence that certain antioxidants and vitamins including zinc, selenium, vitamin C and vitamin E may help men with a low sperm count or poor motility, but more research is needed before they can be said to be proven to work.

The named products, and what they rest on

The most heavily marketed ingredients — coenzyme Q10 and ubiquinol, myo-inositol, maca root, agnus castus or vitex, royal jelly, DHEA, and proprietary antioxidant blends — do not appear as recommendations in NICE NG257, in NHS preconception advice, or on the HFEA's rated list of interventions shown to improve outcomes.

That is not the same as saying they have been proven useless. It means that no UK guideline body has found evidence strong enough to recommend them, which is a lower bar than proof of benefit and a bar they have not cleared. Where individual ingredients are studied at all, trials are typically small, short, use surrogate outcomes such as a laboratory measurement rather than a live birth, and are frequently funded by manufacturers.

Two ingredients deserve specific caution rather than indifference. Herbal preparations can interact with prescribed medicines — the HFEA warns that complementary treatments, particularly herbal medicines, may interact with medicines you are already taking or should not be taken in pregnancy, and advises checking with a healthcare professional first. And DHEA is an androgen precursor, which sits directly against NICE's recommendation not to offer androgens for semen abnormalities.

Who benefits from the claim

Fertility supplements are a good business precisely because the market conditions are ideal for one. The customers are motivated, often frightened, and mostly cannot tell whether the product worked, because a proportion will conceive in any given period regardless. Supplements are regulated as foods rather than as medicines, so a manufacturer does not have to demonstrate efficacy to sell one. Subscription models mean a customer is worth many months of revenue. And clinics, apps and influencers frequently earn commission on the products they recommend.

None of that means any specific product is fraudulent. It means the incentive to make a claim exists independently of whether the claim is true, and that is the reason to ask what the evidence is rather than assuming absence of evidence would have stopped the sale.

The cost that is not money

The more consequential harm is not the monthly bill. It is the implication that conception is a reward for sufficient diligence. If a supplement regime is presented as the thing that will make it happen, then not conceiving becomes something you did — and that is not true. NICE's own cumulative conception data show that most people conceive without changing anything, and time is the main variable.

Supplements can also displace the investigation that would actually help. If you have been trying for a year, or six months if you are 36 or over, or you have irregular or absent periods, a known condition, previous pelvic infection or surgery, the useful next step is a semen analysis and a mid-luteal progesterone test, not a stack.

A reasonable position

Take folic acid, started before conception, and ask whether you are in a higher-dose group.
Consider vitamin D as the NHS advises.
If you want to take something else, treat it as your money and your choice, not as treatment, and tell your clinician what you are taking — particularly anything herbal.
Do not stop or replace prescribed medicine with a supplement.
Be sceptical of anything sold as a course timed to your cycle, or as a subscription.

Fertility Supplements: What the Evidence Actually Shows