Category: Science Explained
The THR mark on a UK herbal medicine looks official, and it is. But it certifies quality, safety and long traditional use, not that the product works. Here is exactly what the MHRA scheme does and does not guarantee, and how to read it.
Category: Science Decoded | Reading time: ~14 min | Level: Beginner
Pick up a box of a herbal remedy in a British pharmacy, a valerian for sleep, a lavender for stress, a St John's wort for low mood, and somewhere on the packaging you will often find three letters and a number: THR, followed by a code. Most people never register it. Those who do tend to read it as a stamp of officialdom, a quiet signal that a regulator has looked at this product and approved it, which by extension must mean it works. That reading is half right and half wrong, and the wrong half is the one that costs shoppers money.
The THR mark is real, it is meaningful, and it is genuinely reassuring about some things. It is also carefully, legally silent about the one thing most people assume it covers. Understanding exactly where that line sits is one of the most useful pieces of label literacy a UK shopper can have, because it turns a vague sense of official approval into a precise understanding of what has and has not been checked.
This piece explains the scheme plainly: what THR stands for, what a manufacturer has to do to earn it, what it certifies, what it deliberately does not, and how it differs from a full medicine licence and from an ordinary food supplement. By the end, a THR mark should tell you something specific and true, rather than something comforting and vague.
THR stands for Traditional Herbal Registration. It is a scheme run by the MHRA, the Medicines and Healthcare products Regulatory Agency, which is the UK body responsible for regulating medicines. A product that has been granted a registration can display a THR number, a nine-character code, and an accompanying THR logo, the certification mark, on its packaging [1][3].
The scheme exists because of a specific regulatory history. It was created under a European directive on traditional herbal medicinal products, adopted in 2004 and brought into full effect in 2011, which set up a dedicated registration route for herbal medicines that had a long history of traditional use [2]. Before it, many herbal products sat in an awkward grey zone, sold widely but without a consistent regulatory framework for quality and safety. The THR scheme brought them into a proper system.
One sentence to anchor the whole thing: a THR registration is granted on the basis of a herbal medicine's quality, its safety, and its documented history of traditional use, and not on clinical proof that it is effective [1]. Everything else in this article is an unpacking of that single, load-bearing sentence.
To earn a THR, a manufacturer has to satisfy the MHRA on three fronts, and it is worth seeing them laid out because they explain both the value and the limits of the mark.
First, quality. The product must be made to appropriate pharmaceutical manufacturing standards, so that the herb in the box is genuinely the herb on the label, at a consistent, specified strength, batch after batch [1][3]. In a supplement market where independent testing regularly finds products that do not match their labels, this is not a trivial assurance.
Second, safety. The manufacturer must provide evidence of an acceptable safety profile, including appropriate warnings and patient information, so that known cautions and interactions are documented and communicated [1]. The product is treated as a medicine for safety purposes, with the monitoring that implies.
Third, traditional use. This is the distinctive one. The manufacturer must show that the product, or a corresponding one, has been used as a herbal medicine for the relevant purpose for at least 30 years, of which generally at least 15 years must have been within Europe [1]. This long-use requirement is the substitute for the clinical trial data a conventional medicine would need.
Notice what is not on that list: a requirement to prove, through clinical trials, that the product actually works. That omission is deliberate, and it is the crux of the whole scheme.
Here is the part that is easy to miss and important to get right. Because a THR is granted on traditional use rather than efficacy, the mark does not certify that the product works [1][2].
The scheme is explicit about this in the wording it permits on the pack. A THR product's indication is phrased along the lines of a traditional herbal medicinal product used for a given purpose based on traditional use only. That closing phrase, based on traditional use only, is the regulator being scrupulously honest: it is telling you that the justification for the claimed use is history, not a demonstration of effect. A regulator has confirmed the herb has long been used this way and is safe and well made. It has not confirmed that a trial showed it helps.
This is why the mark can sit happily on herbs whose modern clinical evidence is genuinely weak. Traditional use and proven effectiveness are simply different claims, and the THR scheme only speaks to the first. A herb can have three centuries of use and a stack of unimpressive trials at the same time, and still, entirely legitimately, carry a THR mark. The mark is not lying to you. It is answering a question, about heritage, quality and safety, that is narrower than the one most shoppers think they are asking, about whether it works.
The THR mark makes most sense when you place it between the two things it sits between.
Above it is a full marketing authorisation, shown by a PL number (product licence). To get one, a manufacturer must prove the product is effective, through clinical trial data, as well as safe and well made [2]. This is the route for conventional medicines and for the small number of herbal products that have chosen to demonstrate efficacy. A PL product has cleared an effectiveness bar that a THR product has not. That is the key difference: both are regulated medicines, but only the PL has shown it works.
Below it is the ordinary food supplement. A supplement is regulated as a food, not a medicine. It carries no THR and no PL, does not have to meet pharmaceutical manufacturing standards, and does not document traditional use. Many herbal products, and all vitamins and minerals like magnesium or vitamin D, are sold this way. A supplement is not necessarily poor quality, but nothing in its status guarantees the quality-and-safety assurances a THR provides.
So the ladder runs: food supplement (no medicine registration), THR (quality, safety and traditional use, but not proven efficacy), and full PL medicine (all of that plus proven efficacy). A THR product is more tightly assured than a supplement and less proven than a licensed medicine. Knowing which rung a product sits on tells you exactly what has and has not been checked.
Turned into a habit, this is quick.
When you pick up a herbal product, look for the registration status. A THR number, nine characters, usually with a small THR logo, tells you it is a registered traditional herbal medicine: quality-assured, safety-assessed, long-used. Read the indication wording, and notice the based on traditional use only phrasing, which is the label reminding you what standard it cleared. If you want to confirm, the MHRA publishes a public list of herbal medicines granted a THR, which you can check a product or ingredient against [5].
Then separate the two questions the mark keeps apart. Is this well made and safe? The THR is good evidence of yes. Does the herb actually work for my symptom? For that, go and look at the clinical evidence for the herb itself, because the mark does not answer it. Some traditionally registered herbs have decent evidence and some have weak evidence, and the THR mark looks identical on both.
Finally, treat the absence of any registration as information too. A herbal product making confident, medicine-like claims with no THR and no PL number has not been through either route, and that is worth a second look.
One genuine safety benefit of the THR scheme is worth stating clearly. Because THR products carry proper patient information and documented warnings, the known cautions and interactions for the herb are communicated on or with the pack, which is often not the case for the same herb sold as an unregulated supplement. That is a real advantage of buying a registered product.
It does not, however, remove the need for the usual care. A registered herbal medicine still interacts with drugs, still has contraindications, and still deserves the same caution as any active substance, particularly alongside prescription medication. The THR mark helps you find that information; it does not make the underlying cautions disappear.
Pregnant, breastfeeding, or on medication? Check with a healthcare professional first.
We spend time on the THR mark because it is a near-perfect example of the thing this whole library exists to do: help you read an official-looking signal for exactly what it says, no more and no less. The mark is honest and useful. It certifies quality, safety and long use, and that is genuinely worth having. It simply does not certify effectiveness, and a great deal of herbal marketing quietly relies on shoppers not knowing the difference.
That is the same discipline we try to hold ourselves to in the Remedy Library, where we separate what a herb is traditionally used for from what the trials actually show, and grade the evidence on its own terms rather than letting a registration or a heritage brand stand in for proof. A THR mark tells you a product is well made and long used. Whether the herb helps you is a separate question, and answering it honestly is the job.
If you want to see the principle applied, our piece on Kalms and valerian looks at exactly this gap between a registered, traditional product and its actual evidence, and our guide to the best natural sleep aids in the UK grades a whole shelf of them. To weigh a specific herbal product against your own situation and medicines, ask Remy.
The FAQ entries above answer the common searches: what the THR mark means, whether it proves a product works, how it differs from a medicine licence and a food supplement, and how to check for one. The short version: THR certifies quality, safety and long traditional use, not effectiveness, so read it as a heritage-and-safety mark and look up the herb's actual evidence separately.
1. MHRA / GOV.UK (2024). Apply for a traditional herbal registration (THR). gov.uk. Regulatory guidance; 30 years traditional use, at least 15 in Europe, quality and safety but not efficacy. 2. European Parliament and Council (2004). Directive 2004/24/EC on traditional herbal medicinal products. Legislation; established the traditional-use registration route, in full effect from 30 April 2011. 3. MHRA (2021). The Traditional Herbal Registration (THR) Certification Mark: guidance for business. Regulatory guidance on the certification mark and its use. 4. MHRA / GOV.UK (2011). Introduction of the Traditional Herbal Registration Certification Mark. Drug Safety Update. Regulatory communication. 5. MHRA / GOV.UK (2024). Herbal medicines granted a traditional herbal registration (THR). gov.uk. Public register of THR products.
THR stands for Traditional Herbal Registration. It is a mark from the UK medicines regulator, the MHRA, shown by a THR number and a small logo on the pack. It tells you the herbal medicine is made to assured quality standards, has an acceptable safety profile, and has a long documented history of traditional use, generally 30 years. What it deliberately does not tell you is that the product has been proven to work, because registration is based on tradition and safety, not on clinical trials of effectiveness.
No, and this is the single most misread thing about it. A THR registration is granted on the basis of traditional use, not evidence of effectiveness. The permitted wording even says so, describing the product as a traditional herbal medicine used for a purpose based on traditional use only. So the mark confirms the product is well made, safe and long used, three genuine assurances, but it is not a statement that a trial showed it helps your symptom. Long use and proven effect are different claims.
A full marketing authorisation, shown by a PL number, requires the manufacturer to prove the product is effective as well as safe and well made, through clinical trial data. A Traditional Herbal Registration is a lighter route created for herbal medicines, which requires quality, safety and evidence of long traditional use, but not proof of efficacy. So a PL medicine has cleared an effectiveness bar that a THR product has not. Both are regulated; only one has demonstrated that it works.
On quality and safety assurance, generally yes. A food supplement carries no medicine registration, is regulated as a food rather than a medicine, and does not have to meet pharmaceutical manufacturing standards or document traditional use. A THR product does. That makes a THR herbal medicine a more tightly controlled product. It still does not mean the THR product is proven effective, so the comparison is about assurance of quality and safety, not about proof that either one works.
Look on the packaging for the letters THR followed by a nine-character registration number, usually alongside a small THR logo. The MHRA also publishes a public list of herbal medicines granted a Traditional Herbal Registration, so you can check a product or ingredient against it. If a herbal product makes medicine-like claims but shows no THR or PL number, that is worth noticing, because it means it has not been through either registration route.
The scheme was created to bring long-used herbal medicines into a proper regulatory framework for quality and safety, without requiring the expensive full clinical trials that a new drug needs, on the basis that a very long history of use provides reassurance about safety. The trade-off is explicit: you get assured quality and safety and a long usage record, but not a demonstration of efficacy. It is a sensible compromise, provided everyone understands that the mark is about heritage and safety, not proof.
Yes, quite a lot, as long as you read it correctly. Assured manufacturing quality means the herb in the box is genuinely the herb on the label, at a consistent strength, made under proper controls, which is far from guaranteed in the unregulated supplement market. An acceptable safety profile and proper patient information matter too. Those are real, valuable assurances. The mark is worth something specific and useful; it is just not worth what many shoppers assume, which is proof of effectiveness.
The THR is a reason to trust its quality and safety, not a reason to expect it to work, so judge the effect on its own terms. Look up the actual evidence for the herb, give it a fair and consistent trial, and decide whether it helps you. Plenty of THR herbs have modest or weak trial evidence despite their long traditional use. The registration is a floor for quality and safety; whether the herb does anything useful for you is a separate question the mark does not answer.
It means the dose and preparation match the traditional use the registration is based on, and that the product is made consistently to that specification, which is genuinely useful. It does not mean that dose has been proven effective in trials, because efficacy is not what the scheme tests. So a THR product gives you a consistent, quality-assured, traditionally used dose, which is a good starting point, rather than a clinically optimised one.