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Last updated: September 2026 · 8 minute read
Men's health · Zinc · Authorised claims
Zinc, Testosterone and Male Fertility: What a Supplement Can Legally Say in the UK
Type "testosterone booster" into any marketplace and you get thousands of results. Not one of them is allowed to say what it says. This guide explains the two zinc claims that are authorised, what they mean, the research behind them, and how to buy a men's zinc supplement without being sold a promise.
Quick answer
Two authorised health claims connect zinc to men's health in Great Britain: zinc contributes to normal fertility and reproduction, and zinc contributes to the maintenance of normal testosterone levels in the blood. Both are maintenance claims. No supplement can lawfully claim to raise testosterone or treat infertility, because testosterone is a medicine and infertility is a medical condition. A zinc supplement providing at least 1.5mg a day can carry both claims; Spermer-Dons provides 8mg (80% NRV) as zinc bisglycinate, with 700mg of L-arginine HCl, one capsule a day. Food supplement, not a medicine.
Why "testosterone booster" is not a thing, legally
Testosterone is a prescription-only medicine in the UK. A product that claims to raise it is claiming a medicinal effect, and a food supplement that does that is an unlicensed medicine by presentation, which is MHRA territory rather than a marketing quibble. That is why the word "booster" does not appear on any authorised claim, for any nutrient, at any dose.
What the register does allow is narrower and more useful. A nutrient can be said to contribute to the maintenance of normal testosterone levels. That wording exists for exactly one nutrient: zinc.
The two zinc claims men actually search for
Zinc contributes to the maintenance of normal testosterone levels in the blood
The evidence behind it runs both ways. When healthy young men were put on a zinc-restricted diet, their testosterone fell over 20 weeks (Prasad et al., 1996). But when men who already had adequate zinc took a high-dose supplement, their testosterone did not change (Koehler et al., 2009). Put those together and you have the claim: zinc holds a normal level normal. It does not push a normal level higher.
Zinc contributes to normal fertility and reproduction
Zinc cannot be stored in the body in any quantity, so it has to come from food or supplements every day, a point Fallah and colleagues make in their 2018 review of zinc in male reproduction. The reproductive system is one of the most zinc-demanding tissues there is, because it depends on cells dividing and DNA being copied correctly, both zinc-dependent processes. The claim covers normal function. It is not a treatment for infertility, and a couple who have been trying without success should see their GP, not a supplement page.
Both wordings were assessed by the European Food Safety Authority in its 2010 scientific opinion on zinc and carried into the Great Britain register. They are fixed; a seller can explain them but cannot extend them.
The rest of the register: 18 zinc claims in total
Zinc has more authorised claims than almost any other nutrient. The ones most relevant to a men's supplement are below, with the legal wording first and our plain-English explanation second.
| Authorised claim | What it means |
|---|---|
| Zinc contributes to normal fertility and reproduction | Zinc-dependent enzymes are involved in copying DNA and in cell division, the machinery behind normal reproductive function in both sexes. The claim is about keeping normal function normal. It is not a claim to treat infertility or to change a semen analysis. |
| Zinc contributes to the maintenance of normal testosterone levels in the blood | The body needs an adequate zinc supply to keep testosterone within its normal range. Maintenance means exactly that: it holds a normal level normal. It does not, and cannot lawfully claim to, raise it. |
| Zinc contributes to the normal function of the immune system | Immune cells need zinc to develop and work as they normally do. |
| Zinc contributes to normal DNA synthesis | Every new cell needs a copy of your DNA, and zinc-dependent enzymes help make that copy. |
| Zinc has a role in the process of cell division | Fast-renewing tissues rely on cells dividing properly, a process zinc takes part in. |
| Zinc contributes to the protection of cells from oxidative stress | Zinc is part of one of the body's own antioxidant enzymes. |
| Zinc contributes to the maintenance of normal hair, skin and nails | Three separate claims on the register, all for fast-renewing tissues with a steady zinc requirement. |
| Zinc contributes to normal cognitive function | The brain's ordinary processes. Not a mood or focus claim. |
The full list of 18, with an explanation of each, is on the Spermer-Dons product page.
How to read a men's zinc supplement label
Once you know the claims are fixed, the only things left to compare are what is in the capsule and whether the label tells you honestly. Four checks:
1. Which zinc?
Zinc oxide and zinc sulphate are cheap and poorly tolerated; sulphate in particular is the usual cause of nausea with zinc tablets. Zinc bisglycinate is zinc chelated to the amino acid glycine and is the form usually chosen where stomach comfort matters. All permitted forms carry the same claims, so the form is a comfort choice, not a claims choice.
2. Compound weight or zinc weight?
A label saying zinc bisglycinate 40mg is telling you the weight of the compound, not the zinc. Bisglycinate is roughly 20% zinc, so 40mg provides about 8mg of zinc. An honest label gives you both figures and the NRV percentage against the zinc, not the compound.
3. Is it under 25mg?
UK guidance is to keep supplemental zinc under 25mg a day, because long-term intake above that reduces copper absorption. Some men's products go well past it. Add up everything, including your multivitamin.
4. What is the other ingredient doing?
Men's formulas often pair zinc with L-arginine, maca, tribulus or fenugreek. None of those has an authorised claim. A seller who is honest about that, and declares them by amount rather than by promise, is telling you something about how they handle the rest of the label.
Spermer-Dons: built on the two claims, and nothing it cannot say 
Spermer-Dons Men's Complex
40mg
zinc bisglycinate
8mg
zinc · 80% NRV
700mg
L-arginine HCl
0
fillers
One capsule a day. 40mg of zinc bisglycinate providing 8mg of zinc, and 700mg of L-arginine hydrochloride providing about 579mg of L-arginine, both figures on the label. Vegan HPMC shell, no fillers, no hormones, no stimulants, no herbal extracts. Plain packaging, same-day dispatch before 3:30pm.
Six pack sizes from 60 to 500 capsules, from £8.99. At one a day, the 500 pack works out at 7.8p a day.
View Spermer-DonsView on eBayWant zinc without the L-arginine? Our Triple Zinc + Copper tablets carry the same 18 claims with copper added. Choose one zinc product, not both.
Before you take any zinc and L-arginine product
Speak to your doctor or pharmacist first if you
take medicines for blood pressure, angina or the heart, including nitrates (L-arginine can add to their effect) · have had a heart attack · have kidney disease · are prone to cold sores · take antibiotics (leave two hours between them and zinc) · take any regular medication. Not suitable for under 18s, or during pregnancy or breastfeeding.
And for everyone
Take zinc after food, never on an empty stomach. Keep total supplemental zinc under 25mg a day. Food supplement, not a medicine: if you have a concern about testosterone or fertility, that is a GP conversation, and a blood test costs nothing on the NHS.
The claims are the product
Zinc for normal testosterone and normal fertility, declared properly, one capsule a day. 5 Star Food Hygiene Rating · 164,000+ verified sales · UK supplier since 2016.
Shop Spermer-DonsZinc, testosterone and fertility: frequently asked questions
Does zinc boost testosterone?
No supplement can lawfully claim that. The authorised claim is that zinc contributes to the maintenance of normal testosterone levels in the blood. In men who already get enough zinc, extra zinc did not raise testosterone in a 2009 study. In men who were made zinc-deficient, testosterone fell. Zinc keeps a normal level normal.
Does zinc help male fertility?
The authorised claim is that zinc contributes to normal fertility and reproduction. Zinc is needed for the body's normal reproductive processes. It is not a treatment for infertility, and anyone who has been trying to conceive without success should speak to their GP.
What is a testosterone booster, legally?
In Great Britain there is no such thing. Testosterone is a controlled medicine, and no food supplement is authorised to claim it raises testosterone. Products sold as boosters are making an unauthorised claim, whatever the ingredients.
What form of zinc is best?
Zinc bisglycinate is zinc chelated to the amino acid glycine. It is the form usually chosen where stomach comfort matters, because unchelated zinc salts such as sulphate are the usual cause of nausea with zinc supplements. All permitted forms carry the same authorised claims.
How much zinc do I need for the claims to apply?
Any authorised zinc claim can be used once a daily serving provides at least 15% of the nutrient reference value, which is 1.5mg. Spermer-Dons provides 8mg (80% NRV) in one capsule.
Can I take too much zinc?
UK guidance is to keep supplemental zinc under 25mg a day. Long-term intake above that can reduce copper absorption. Add up the zinc in any multivitamin you take.
Does L-arginine have health claims?
No. Claims for L-arginine were assessed by the European regulator and none was authorised, so none is used in Great Britain. In Spermer-Dons it is declared as an ingredient at 700mg of L-arginine HCl, about 579mg of L-arginine, and nothing is claimed for it.
Who should not take Spermer-Dons?
Under 18s, and anyone pregnant or breastfeeding. Speak to your doctor or pharmacist first if you take medicines for blood pressure or the heart (including nitrates), have kidney disease, are prone to cold sores, or take any regular medication.
References
Background to the authorised zinc claims. Educational context only; the only health claims made are the authorised Great Britain claims for zinc.
1. Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344-8. 40 men; 4 young men in the zinc-restriction arm; 9 older men supplemented. PubMed 8875519
2. Koehler K, Parr MK, Geyer H, Mester J, Schänzer W. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009;63(1):65-70. 14 healthy men with adequate zinc; no change in testosterone. doi.org/10.1038/sj.ejcn.1602899
3. Fallah A, Mohammad-Hasani A, Hosseinzadeh Colagar A. Zinc is an Essential Element for Male Fertility: A Review of Zn Roles in Men's Health, Germination, Sperm Quality, and Fertilization. J Reprod Infertil. 2018;19(2):69-81. Review. PubMed 30009140
4. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to zinc. EFSA Journal. 2010;8(10):1819. doi.org/10.2903/j.efsa.2010.1819
Disclaimer: Food supplement, not a medicine. Not intended to diagnose, treat, cure or prevent any disease or condition, including infertility or low testosterone. Health claims in this article are the authorised Great Britain claims for zinc; no claims are made for L-arginine. Research references are for background only. Not suitable for under 18s, or during pregnancy or breastfeeding. Consult your doctor or pharmacist before use if you take any medication or have a medical condition. Keep total supplemental zinc under 25mg a day. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. Charge Products is a trading name of Big Idea Services Ltd, Company No. 11645389, Unit 1, 8 Towerfield Road, Towerfield Industrial Estate, Southend-on-Sea, Essex SS3 9QE.
