Dietary Supplement vs Medicine: What is the Difference and How Not to Be Deceived

On the pharmacy shelf, two green magnesium capsules stand next to each other. They look the same, cost similarly, and are separated by a regulatory chasm: one had to undergo clinical trials, while the other only required notification to the office. The Supreme Audit Office calculated that from 2017 to 2020, the Chief Sanitary Inspectorate received nearly 63 thousand notifications about supplements and analyzed 11 percent of them. Therefore, the verification of the label falls on the buyer. From this text, you will learn what distinguishes a supplement from a medicine in the eyes of the law, what must be on the packaging, what the manufacturer is not allowed to write, how to compare two products with the same declared dose, and which combinations with prescription medications require a conversation with a doctor.

KEY INFORMATION
• From 2017 to 2020, GIS received nearly 63 thousand notifications about supplements, analyzing 11 percent of them (NIK, 2022).
• A supplement is food and does not have to prove effectiveness. A medicine must, in clinical trials phases I-III.
• Regulation (EC) No 1924/2006 prohibits attributing healing properties to food or preventing diseases.
• The same dose of vitamin D3 can cost five times more when converted to 1000 IU.

What is the difference between a dietary supplement and a medicine in the eyes of the law?

A dietary supplement is, under Polish and EU law, food, not a medicinal product. The manufacturer submits a notification to the Chief Sanitary Inspectorate and can start selling the same day. A medicine undergoes registration with URPL or EMA and must prove its effectiveness and safety in clinical trials beforehand.

The basis for supplements is Directive 2002/46/EC and the Act of August 25, 2006, on food safety and nutrition. Medicines are regulated by the Pharmaceutical Law of September 6, 2001. Registering a medicine takes years of work and money, which a product priced at twenty zlotys will not return. This explains why a manufacturer of the same substance often chooses the food route.

This difference does not mean that a supplement is inferior by definition. It means that the proof of quality is provided voluntarily by the manufacturer, and finding it is the buyer’s responsibility.

What does GIS check when notifying a supplement, and what does it not?

The Inspectorate verifies whether the product fits the definition of a supplement, whether the ingredients are permitted, and whether the label meets formal requirements. It does not assess whether the product works and does not check before sale whether the capsule contains as much substance as the packaging claims.

The scale of this gap was shown in the report of the Supreme Audit Office from January 18, 2022. From 2017 to 2020, nearly 63 thousand notifications were received by GIS, and by May 2021, 11 percent of them were analyzed. Investigative proceedings did not start for nearly 56 thousand notifications. It was handled by at most seven employees, which means about 300 notifications per month per person. The longest verification described in the report lasted over 13 years and 10 months.

Sample checks of already sold products included from 4.1 to 4.3 thousand supplements annually, of which 5-6 percent were disqualified. These are data from Poland, so they refer to your shelf, not the American market. The practical conclusion is simple: admission to sale is not any certificate of quality, as the office in most cases simply did not have time to read the notification.

What must be on the label of a dietary supplement?

The range of mandatory information is defined by Regulation (EU) No 1169/2011 and national regulations. The packaging must include the term “dietary supplement”, the composition with the amount of active substances in the recommended daily portion, and a set of warnings.

• The term “dietary supplement” as a category name, not just a trade name.
• Names of active ingredients along with the amount in the recommended daily portion.
• A warning not to exceed the recommended daily portion.
• Information that the supplement does not replace a varied diet.
• A note about keeping it out of reach of small children.
• The percentage of reference intake values for vitamins and minerals.

What does not have to be on the label: the GIS notification number. A medicine has a number of approval for market entry printed on the box, while a supplement does not need such an identifier, which makes it difficult to check it in the register. There is also no obligation to provide the chemical form of the ingredient, which determines absorption. When purchasing from platforms outside the European Union, there is one more risk: without notification to GIS, the product is not subject to any supervision in Poland, and the responsibility for the consequences falls on the buyer.

What cannot the supplement manufacturer write on the packaging?

Regulation (EC) No 1924/2006 allows only health claims approved after EFSA assessment. Statements like “vitamin C contributes to the proper functioning of the immune system” are allowed because they have a number on the EU list.

Everything that suggests curing a disease or preventing it is prohibited: “cures arthritis”, “lowers the risk of heart attack”, “fights cancer”. Such a message turns a supplement into a medicinal product introduced to the market without permission, which is already dealt with by the sanitary inspection and URPL. In practice, manufacturers circumvent the ban with soft language: instead of “cures insomnia”, it appears as “supports calm sleep”. The line can be thin, but the rule for the label reader is clear. A disease name next to a verb indicating action is a signal that something is wrong.

A tougher version of this problem is the falsification of the composition. An analysis of warnings from the American FDA from 2007-2016 described in JAMA Network Open (Tucker et al., 2018) found 776 supplements with undeclared medicinal substances. This most often concerned products for potency, weight loss, and bodybuilders, and in weight loss products, in 84.9 percent of cases, it was about sibutramine, withdrawn from the market in 2010.

How much does the same dose of vitamin D3 cost in our store?

The declared dose on the packaging says nothing about the price per unit of substance. We calculated four packages of vitamin D3 from our catalog for the cost of 1000 IU, and the range turned out to be fivefold, even though all four products are regular cholecalciferol.

Prices are from our store, as of August 8, 2026. A dose of 10000 IU is not a daily dose and requires monitoring of vitamin D levels in the blood, so the column with the unit cost is here for comparing packages, not for choosing a dose.

What besides price determines the value of a supplement?

The cost per unit of substance is the first sieve, not the last. The second is the chemical form, as it determines how much of the declared dose is actually absorbed. The chart below shows how far apart the converted prices from the previous table are.

In our supplement catalog, there are 174 items, and you can see two schools of description. Some provide the form directly in the name, such as potassium citrate or magnesium in three forms. Others end with the word “magnesium”, leaving the buyer without information. Magnesium oxide is poorly absorbed, while citrate and diglycinate are much better. The same applies to folic acid: the conversion to the active form is limited by the MTHFR gene variant, which in a study of 1712 adult Poles (Wrzosek and Ślusarczyk, Biomedicines 2022) occurred in 8.6 percent in the homozygous form and in 44 percent in the heterozygous form. For more than half of the population, folate in the methylated form is therefore a better choice than regular folic acid.

When to choose a supplement and when a medicine?

A supplement makes sense where you are supplementing a deficiency or diet: vitamin D3 in months without sun, vitamin B12 on a plant-based diet, magnesium with a diet low in vegetables and seeds. You choose a medicine when treating a diagnosed disease.

The division is sharper than suggested by the pharmacy shelf, where both stand next to each other. In iron deficiency anemia, you need a medicinal product in a dose tailored after testing morphology and ferritin, not an iron tablet “for strengthening”. In a bacterial infection, you need an antibiotic, not a probiotic. Attempting to treat an active disease with a supplement delays proper therapy, and in the case of cancer or heart failure, every lost week has clinical significance.

A separate category is herbal medicines. A standardized extract of valerian or a product from horse chestnut can be registered as a medicinal product, with studies and a ChPL. It looks like an herb from the shelf next to it, but it has gone through a different path and should not be confused with a supplement of similar composition. You will recognize it by the approval number on the packaging and the patient leaflet.

Which supplements interact with prescription medications?

The manufacturer of a medicine is obliged to describe interactions in the ChPL. The manufacturer of a supplement does not have such an obligation, so you will usually not find warnings on the packaging, even when the risk is real and well documented in the literature.

The best-documented case is St. John’s wort. A review by Nicolussi et al. in the British Journal of Pharmacology (2020) confirms that extracts of St. John’s wort activate the PXR receptor and induce CYP3A4 and P-glycoprotein, thereby lowering the concentration of cyclosporine, tacrolimus, indinavir, warfarin, alprazolam, simvastatin, and hormonal contraceptives. The strength of the effect depends on the content of hyperforin, and the authors did not record clinically significant interactions at doses up to 1 mg of hyperforin per day. The problem is that the content of hyperforin does not have to be stated on the supplement label.

The list does not end with St. John’s wort. Vitamin K weakens the effect of warfarin, and high doses of vitamin E and omega-3 fatty acids can enhance it. Vitamin C at doses above 2 g increases iron absorption, which can be dangerous in hemochromatosis. Before adding anything to your regular pharmacotherapy, check for interactions in the NIH Office of Dietary Supplements database or ask a pharmacist, as in Poland, they are obliged to provide such information. We have also gathered a set of practical rules in the post about NAC and its combination with medications.

Why should your doctor know about your supplements?

Because they often do not know. In a study by Chiba et al. published in Nutrients (2015), among 1508 patients combining supplements with medications, 70.3 percent did not inform either their doctor or pharmacist. The most common reason was the belief that such a combination is safe anyway.

A simple rule organizes the matter: include supplements on the same list as medications. When regularly taking more than two prescription preparations, ask the pharmacist for a medication review, which is a scheduled conversation in which the entire therapy is checked, not just a single package. Before a planned surgical procedure, submit the list to the anesthesiologist, as omega-3 fatty acids, vitamin E, garlic, ginseng, and ginkgo biloba affect blood coagulation and require prior discontinuation. Write down the trade name along with the dose, not just the ingredient. Without the dose, no one can assess whether we are talking about preventive dietary supplementation or an amount that will change the effect of the medicine.

It is worth transferring the same caution to supplementation in competitive sports, where the risk of interactions comes with the risk of a doping result. We described this in more detail in the text about supplements for athletes compliant with regulations.

Frequently Asked Questions

Below are answers to questions that frequently arise when comparing supplements with medicines.

What is the difference between a dietary supplement and a medicine?

A medicine undergoes registration with URPL or EMA and must prove its effectiveness and safety in clinical trials. A dietary supplement is food: the manufacturer submits a notification to GIS and can start selling immediately, without evidence of efficacy. A medicine has a Product Characteristics Document with indications, dosage, and interactions, while a supplement does not have such a document.

What must be on the label of a dietary supplement?

Mandatory: the term “dietary supplement”, names of active ingredients with amounts in the recommended daily portion, a warning not to exceed the portion, information that the supplement does not replace a varied diet, and a note about keeping it out of reach of children. For vitamins and minerals, the percentage of reference intake values must be provided. The GIS notification number does not have to be on the packaging.

How to check if a supplement is safe?

Look for the manufacturer’s address in the European Union, a GMP certificate of the facility, and the batch test result, i.e., Certificate of Analysis. You can find the product in the GIS notification register. Athletes should additionally choose products with the Informed Sport certification or from the Cologne List, as only they are tested for substances banned by WADA.

Can a supplement claim to cure?

No. Regulation (EC) No 1924/2006 prohibits attributing healing properties to food or preventing diseases. Only health claims from a list approved after EFSA assessment are allowed, for example, about the role of vitamin C in the proper functioning of the immune system. The words “cures” or “fights” next to a disease name are a warning signal.

What is an OTC medicine, and what is a supplement?

An OTC medicine is available without a prescription but remains a legitimate medicinal product with URPL approval and proven effectiveness. A supplement is food after notification to GIS, without such a requirement. Both may contain the same substance, but only a medicine is subject to pharmacovigilance and has clinical indications recorded in the ChPL.

Which supplements should be discontinued before surgery?

Before a planned procedure, discontinue products affecting coagulation: high doses of omega-3 fatty acids, vitamin E, garlic, ginseng, ginkgo biloba, and St. John’s wort. The timing is determined by the anesthesiologist, usually from one to two weeks before the surgery. Include supplements on the same list as medications that you submit before the procedure.

If you want to compare labels on specific products, check the supplements section.

The article is for informational and educational purposes and does not constitute medical advice. Before starting supplementation, consult your doctor, especially if you are taking medications regularly, are pregnant or breastfeeding, or have a chronic illness.

Author: Michał Waluk · Published: 2026-05-20 · Updated: 2026-08-08