Written and maintained by CASRAI Editorial Board
Last updated
Short answer: an NDC (National Drug Code) is the unique three-segment number that serves as the FDA’s identifier for a drug product. Its segments identify the labeler, the product and the package size and type. It is a listing identifier, not a mark of FDA approval, and it is assigned only to drugs, not to non-drug products.
This guide is general reference information for lab, clinic and purchasing staff. It is not medical advice and not a substitute for the FDA’s own directory or your payer’s billing instructions.
What an NDC is and what it covers
Under 21 CFR 207.33, the NDC identifies the labeler, the product and the package size and type, and each listed finished or unfinished drug needs its own unique NDC. The FDA’s NDC Directory page describes it as a unique, three-segment number that serves as the FDA’s identifier for drugs. FDA training material adds that an NDC should not be assigned to non-drug products. That matters for supply teams: an item stocked next to drugs, such as a device, a dressing or a lab consumable, does not get an NDC just because it sits on the same shelf. For devices, the identifier system is different; see unique device identification (UDI).
How an NDC is structured: labeler, product and package code
What does an NDC number mean?
Each of the three segments carries a different piece of information, and two of them are proposed by the labeler rather than set by the FDA.
- Labeler code: identifies the manufacturer, repacker, relabeler or private label distributor. Per 21 CFR 207.33 it is 4, 5 or 6 digits and is assigned by the FDA. This is the answer to “what is an NDC labeler code”.
- Product code: 3 or 4 digits. FDA material describes it as identifying the specific strength, dosage form and formulation of a drug, and the labeler proposes it.
- Package code: 1 or 2 digits. It identifies the package type and size, and is also proposed by the labeler. A change to package size or type alone calls for a new package code; a change to the drug’s name, active ingredient strength or dosage form calls for a new product code.
How is an NDC structured (5-4-2, 4-4-2, 5-3-2)?
Segment lengths are not free. 21 CFR 207.33 permits five configurations, and a labeler must use only one product-package code configuration across its NDCs.
| Labeler code length | Permitted configuration (labeler-product-package) | Total digits |
|---|---|---|
| 4 digits | 4-4-2 | 10 |
| 5 digits | 5-3-2 or 5-4-1 | 10 |
| 6 digits | 6-3-2 or 6-4-1 | 11 |
Notice what is missing: 5-4-2 is not one of the configurations in 21 CFR 207.33. It appears in billing, where it is a derived format (next section).
10-digit vs 11-digit NDC
The FDA’s NDC training presentation explains the difference. An 11-digit NDC is a derivative in which zeros are added to reach a fixed-length 5-4-2 configuration. The same presentation states that under HIPAA covered transactions, NDCs are to be reported in the 11-digit format, and that some government agencies and private payers also require it. So the 10-digit form is how many numbers are assigned and printed under the regulation, while the 11-digit 5-4-2 form is a fixed-width form used when reporting. Both describe the same product; confirm which format a given payer or system expects before keying a number in.
What the NDC Directory covers, and what it leaves out
The FDA’s National Drug Code Directory (page current as of 4 March 2026, checked 30 October 2026) lists active and certified finished and unfinished drugs submitted through SPL listing files. It includes prescription and over-the-counter drugs, approved and unapproved, and repackaged or relabeled products. It is updated daily, and an entry stays until its marketing end date even if the product is delisted. For the underlying file format, see structured product labeling (SPL).
The same page lists what the Directory excludes: animal drugs, blood products, drugs made under contract, and drugs marketed only as part of a kit or combination product, or as a non-marketed inner layer. It says the Directory does not contain every listed drug. That scope statement is the main reason a kit or a drug-device combination may not show up in a lookup.
For code lookups, use the FDA’s National Drug Code Directory directly; it is the authoritative search tool, and this guide explains the number rather than replacing the tool.
Where it matters for supply decisions
A short checklist, each item taken from the FDA’s own statements:
- An NDC is not approval. The FDA states that assignment of an NDC does not in any way denote FDA approval of the product.
- The Directory is not verified. The FDA states that inclusion in the Directory does not indicate that the FDA has verified the information provided.
- It is not coverage. Inclusion in the Directory does not mean a payer covers the product.
- Not every drug-adjacent item has one. NDCs cannot be assigned to non-drug products, and kits and combination products may be absent from the Directory.
- A new package can mean a new NDC. Because the package code reflects package size and type, a different pack of the same product carries a different package code.
For how drug identifiers connect to distribution rules, see the Drug Supply Chain Security Act and DSCSA compliance requirements for distributors.
Common misunderstandings
- “The NDC proves the drug is FDA approved.” It does not; see the FDA statement above.
- “The NDC is always 11 digits.” As assigned under 21 CFR 207.33 it is 10 or 11 digits depending on labeler code length; the fixed 5-4-2 form is the reporting derivative.
- “Any medical supply has an NDC.” Only drugs do. Devices use other identifiers.
- “The format is permanent.” The FDA has adopted a final rule for a uniform 12-digit NDC format, which its Directory page says takes effect March 7, 2033.
FAQ
What does an NDC number mean?
It is the FDA’s three-segment identifier for a drug: labeler, product and package. It tells you who lists the product, which strength and dosage form it is, and which package size or type it is.
How is an NDC structured?
Under 21 CFR 207.33, the permitted configurations are 4-4-2, 5-3-2, 5-4-1, 6-3-2 and 6-4-1, and a labeler uses one configuration across its NDCs. The 5-4-2 form is the 11-digit reporting derivative.
What is the difference between a 10-digit and 11-digit NDC?
The 10-digit form is how many NDCs are assigned; the 11-digit form adds zeros to reach 5-4-2 and is what HIPAA covered transactions call for, per FDA training material.
Where do I look up an NDC?
Use the FDA National Drug Code Directory, which is updated daily. A product missing from it may be a kit, a combination product, a contract-made drug or another excluded category.
Sources
- 21 CFR 207.33, What is the National Drug Code (NDC), how is it assigned, and what are its requirements? (eCFR, checked 30 October 2026): ecfr.gov
- FDA, National Drug Code Directory (page current as of 4 March 2026, checked 30 October 2026): fda.gov
- FDA CDER, The National Drug Code (NDC): Rules for Assigning and Changing NDCs, training presentation (checked 30 October 2026): fda.gov/media/154502
