Many medicines on this site show a code such as N02BE01. It looks complicated, but you can read it step by step. Each part of the code narrows down where the medicine belongs – from the part of the body it acts on to the exact active substance.
The code comes from the ATC classification (Anatomical Therapeutic Chemical). It sorts active substances by the organ or body system they act on, by how they work and by their chemical type. A World Health Organization (WHO) collaborating centre runs it. Its main purpose is to monitor and study how medicines are used, in order to improve their use.
The five levels, shown on paracetamol
An ATC code has up to 7 characters and five levels. There are 14 main groups. Each level makes the group narrower:
| Code | Level | Meaning |
|---|---|---|
| N | 1st level – main group | Nervous system |
| N02 | 2nd level | Analgesics (painkillers) |
| N02B | 3rd level | Other analgesics and antipyretics (medicines for pain and fever) |
| N02BE | 4th level | Anilides (a chemical group) |
| N02BE01 | 5th level – substance | Paracetamol |
Levels 2 to 4 describe what the medicine is used for, how it works or what chemical group it belongs to. What these levels mean can differ between main groups.
Combinations of substances have their own codes. For example, paracetamol combined with other substances has the code N02BE51. The exception is paracetamol combined with psycholeptics (a group of medicines that includes antipsychotics, medicines for anxiety, sleeping tablets and sedatives). That combination has the code N02BE71.
How ATC codes can help you
- You can find medicines with the same active substance under other names. They usually have the same 5th-level code (except substances with more than one code – see below).
- You can see which group of medicines your medicine belongs to and which other substances are in the same group.
- Texts that mention groups of medicines (for example “proton pump inhibitors”) are easier to follow.
What an ATC code does not tell you
- Whether medicines can be swapped. The WHO says that being in the same group does not show how well a medicine works compared with others. The WHO also says that the ATC system alone is not suitable for decisions about who pays for a medicine, what it costs or whether to replace one medicine with another. Talk to your doctor or pharmacist before you change a medicine.
- Every use of a substance. A substance is classified by its main medical use or by how it works. Some substances have more than one code. The WHO gives a substance more than one code when it is used in different ways (for example taken by mouth or put in the eye) for different purposes. In a few cases it also gives different codes for different strengths. For example, prednisolone for use in the whole body (by mouth or injection) has the code H02AB06, and prednisolone for the eye has the code S01BA04. Prednisolone on its own has several more codes for other uses. Aspirin (acetylsalicylic acid) is also in more than one group, for example N02BA01 as a painkiller and B01AC06 as a medicine that stops blood cells called platelets from sticking together.
- A recommendation. The WHO states clearly that being listed in the ATC classification is not a recommendation to use a substance.
ATC codes on this site
- All ATC groups as a tree of levels 1 to 3. From there you can go to the groups and substances.
- A group page shows its subgroups, its active substances and the medicines with a patient leaflet or SmPC on this site.
- In the “Facts about …” box under a leaflet, the row “Drug group (ATC)” shows a tree from level 1 to level 5.
Most codes come from the NHS Dictionary of Medicines and Devices (dm+d), which gives an ATC code to the general (generic) entry of a medicine where one is available. For some groups we add our own explanation of the name in plain English (“plain English: …”).
More guides: How to read a patient leaflet · Glossary · Brand-name and generic medicines
Sources
We based this page on these documents and checked the facts against them on 4 November 2026. For each one we say what we took from it.
- WHO Collaborating Centre for Drug Statistics Methodology: ATC – Structure and principles – the five levels, the 14 main groups, what levels 2–4 mean, classification by the main therapeutic use, codes of combinations (N02BE51), several codes for one substance by route of administration and, in a few cases, strength.
- WHO Collaborating Centre: Purpose of the ATC/DDD system – the purpose (drug utilisation monitoring and research to improve the quality of drug use); the ATC/DDD system by itself is not suitable for decisions on reimbursement, pricing and therapeutic substitution; a classification is not a recommendation for use and says nothing about efficacy.
- WHO Collaborating Centre, ATC/DDD Index: N02BE01 paracetamol, N02BE51 paracetamol, combinations excl. psycholeptics, N02BA01 and B01AC06 (acetylsalicylic acid; B01AC = platelet aggregation inhibitors), H02AB06 (prednisolone, systemic corticosteroids) and S01BA04 (prednisolone, ophthalmologicals), N02BE71 (paracetamol, combinations with psycholeptics), N05 psycholeptics (antipsychotics, anxiolytics, hypnotics and sedatives).
- World Health Organization (WHO): Anatomical Therapeutic Chemical (ATC) Classification – products with prednisolone as a single ingredient have several codes; active substances divided into groups by the organ or system they act on and their therapeutic, pharmacological and chemical properties, at five levels.
- NHS Business Services Authority: dm+d data model (DOCX) – the dm+d gives an ATC code (up to 7 characters) to its general medicine entries (VMPs) where available.
This page explains the WHO ATC classification and does not replace advice from a doctor or pharmacist. Last updated 4 November 2026. Found a mistake? Email us at info@patient-info.co.uk.