How to Check a Supplement Before You Buy: A UK Checklist

Why checking matters

Food supplements are sold as foods, not medicines. In the UK they are not tested and licensed in the way medicines are, and many products sold online are made and marketed overseas, where labelling and advertising rules differ. That does not make every supplement useless or unsafe, but it does mean the work of checking falls largely on the buyer. The steps below take ten to fifteen minutes and can save money and avoid problems.

Step 1: Find the full label, with doses

A trustworthy product shows its complete ingredient list and the amount of each active ingredient per daily serving, usually in a “Supplement Facts” or nutrition panel. Look for:

• every ingredient named, not “a proprietary blend” or “14 powerful ingredients” with only some listed;
• amounts per serving in milligrams (mg) or micrograms (µg);
• the serving size (for example, two capsules) and servings per container, so you can work out the daily cost;
• the form of the ingredient where it matters (for example, the plant part or the extract standardisation).

If the sales page does not show the label, look for it elsewhere on the official site or ask the seller before buying. Some of the products we have reviewed publish full labels (Joint Glide is one example); others do not, which we treat as a significant gap (see our VivoGut Pro review).

Step 2: Compare doses with UK guidance

For vitamins and minerals, the NHS publishes guidance on how much is likely to be safe from supplements. Add up everything you take, including multivitamins. Some examples from NHS pages:

Nutrient	NHS guidance for supplements
Vitamin B6	Do not take more than 10mg a day unless advised by a doctor
Zinc	Do not take more than 25mg a day unless advised by a doctor
Iodine	0.5mg (500µg) or less a day is unlikely to cause harm
Vitamin E	540mg (800 IU) or less a day is unlikely to cause harm

Seaweed ingredients such as kelp and bladderwrack deserve particular care, because their iodine content varies widely and is often poorly labelled. A 2021 study of kelp and seaweed products found iodine in supplements ranging from 5 to 5,600 micrograms per daily dose (Aakre and colleagues, 2021).

For herbal ingredients, there is usually no official safe limit. Instead, compare the dose with the amounts used in research: an ingredient that sounds impressive may be present at a fraction of the studied dose.

Step 3: Check the claims

In Great Britain, food supplements may only make health claims that have been authorised and listed on the government’s nutrition and health claims register. Separately, the MHRA explains that a product presented as preventing or treating disease is regarded as a medicine, and that herbal or “natural” ingredients do not change that (MHRA borderline products guidance).

Products sold from overseas websites often ignore these rules. Treat these phrases as warning signs:

• “cures”, “reverses”, “heals”, “rebuilds cartilage”, “repairs the gut lining”;
• “works in seconds” or “results in 7 days”;
• “the one root cause” of a common problem, or “doctors don’t want you to know”;
• “detox” or “flushes toxins” (your liver and kidneys already do this);
• works “regardless of your diagnosis”.

Step 4: Look for independent evidence at the same dose

Sales pages often list dozens of research links. Ask three questions:

1. Is the study about this product, or just one ingredient? A study of ginger does not show that a ginger-containing blend works.
2. Was it in people, and was it randomised and placebo-controlled? Laboratory and animal studies are a starting point, not proof.
3. Does the dose match? A trial of 1,500mg a day does not support a product containing 200mg.

Systematic reviews, which pool the results of several trials, are the most useful single source. For example, a 2018 meta-analysis of supplements for osteoarthritis found some short-term benefits but rated the overall quality of the evidence as very low, and found glucosamine and chondroitin to be ineffective or of small, arguably unimportant benefit (Liu and colleagues, 2018). PubMed, the free database run by the US National Library of Medicine, lets you search for these reviews yourself.

Independent UK guidance is also worth checking. For osteoarthritis, NICE recommends exercise and topical anti-inflammatory gels rather than supplements, and the NHS no longer prescribes glucosamine or chondroitin.

Step 5: Check safety and interactions

Ask a pharmacist before starting a supplement if you take regular medicines, are pregnant or breastfeeding, have a long-term condition or are due to have surgery. Some common examples from the products we have researched:

• Ashwagandha should be avoided in pregnancy and while breastfeeding, is not recommended for people with thyroid or autoimmune disorders, and has been linked rarely to liver injury (US National Center for Complementary and Integrative Health).
• Willow bark contains salicylates, related to aspirin.
• Glucosamine has been associated with increased bleeding risk in people taking warfarin and may raise blood sugar in some people.
• Black pepper extract (piperine), added to boost absorption, can also change how some medicines are absorbed.
• Biotin at high doses can interfere with some blood tests; tell your doctor if you take it.

Step 6: Work out the real cost and the terms

• Daily cost: divide the price by the number of days a bottle lasts.
• Bundles: many sites push three or six bottles. Start with the smallest option until you know the product suits you.
• Subscriptions: look for “subscribe and save” boxes that are ticked by default.
• Upsells: extra offers may appear after you enter payment details; read each screen.
• Refunds: check how long you have, whether you must return the bottles and who pays the postage. Returning goods to the US from the UK can be expensive.
• Delivery to the UK: confirm the product ships here. For goods sent from abroad, you may have to pay VAT or customs duty before delivery (GOV.UK guidance).
• Anchor prices: crossed-out “regular prices” and countdown timers are sales techniques. Judge the price you would actually pay.

A worked example: reading one label

Here is how the checks work in practice, using the published label of a joint supplement we have reviewed, Joint Glide. One serving is two capsules and a bottle holds 30 servings.

• Label: all ten ingredients and their amounts are listed. That passes Step 1.
• Doses against guidance: zinc 10mg and vitamin B6 0.5mg are both below the NHS figures for supplements (25mg and 10mg a day). If you already take a multivitamin, add those amounts too.
• Doses against research: glucosamine is 200mg, while the large US GAIT trial used 1,500mg a day (Clegg and colleagues, 2006), and NICE advises not offering glucosamine for osteoarthritis anyway.
• Claims: the sales page says the formula rebuilds cartilage. That goes beyond any evidence we found and beyond what a food supplement may claim in Great Britain.
• Safety: white willow bark (salicylates), glucosamine and black pepper extract all raise interaction questions for people on blood thinners or other regular medicines.
• Cost: one bottle at $69 lasts 30 days, about $2.30 a day before delivery. The six-bottle offer at $49 a bottle works out at about $1.63 a day, but commits you to $294 up front.

The result is a product with a clear label, some ingredients with modest evidence, overstated claims and real interaction cautions: useful information before you decide, and very different from the impression the sales page gives.

Printable checklist

Check	Good sign	Warning sign
Label	Full ingredient list with doses	Hidden or partial formula
Doses	Within NHS guidance; similar to studied amounts	Unknown or far below studied amounts
Claims	Modest, specific wording	Cures, reverses, detox, “in seconds”
Evidence	Independent human trials or reviews	Only ingredient studies or testimonials
Safety	Clear warnings and contact details	“Safe for everyone”, no warnings
Terms	Single-bottle option, clear refund steps	Default subscriptions, costly returns

When to see a GP instead

Supplements are not a substitute for diagnosis. See a GP if a symptom is new, severe or persistent, or if you notice weight loss without trying, blood in your poo or vomit, difficulty swallowing, or a hot, swollen joint. For urgent concerns, call 111.

Frequently asked questions

Are supplements sold online in the UK checked before sale?

Food supplements are regulated as foods, not licensed like medicines. Products sold from overseas websites may not follow UK labelling or claims rules.

Is “made in an FDA-registered facility” a mark of approval?

No. Registration of a facility with the US Food and Drug Administration is not approval of the product or its claims.

How do I find research on an ingredient?

Search PubMed for the ingredient name plus “systematic review”, and check NHS or NICE pages for UK guidance on the condition.

Should I trust customer testimonials?

Testimonials on sales pages cannot usually be verified and are often selected or edited. Many pages state in small print that results are not typical.

Our reviews that use this checklist

• VivoGut Pro review
• Joint Glide review
• Insta Soothe review
• Synevra UltraLift review