NDC, GTIN & NDC12 Reference

The National Drug Code (NDC) is the FDA's standard unique identifier for drugs marketed in the United States. Established under Section 510 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 360), the NDC is required for every drug product intended for commercial distribution.

What the NDC Identifies

The NDC is a three-segment numeric code, where each segment carries distinct meaning:

Coverage

The NDC covers: human prescription drugs, over-the-counter (OTC) drugs, approved and unapproved drugs, repackaged and relabeled drugs, and compounded drugs from 503B outsourcing facilities.

Excluded: animal drugs (separate directory), blood products, drugs not intended for commercial distribution.

The current FDA-assigned NDC is a 10-digit, 3-segment number. The total digit count across all three segments is always 10, but the number of digits in each segment varies. Per 21 CFR 207.33(b), three valid configurations exist:

The 11-digit NDC was not created by FDA. It originated from the HIPAA Administrative Simplification final rule (August 17, 2000 — 65 FR 50312). When HHS adopted the NDC as the standard medical data code set for drugs in electronic transactions, it established a uniform 11-digit format to conform with customary practice used in computer systems.

The 5-4-2 Fixed Format

The HIPAA 11-digit NDC is always 5-4-2: Labeler (5) + Product (4) + Package (2) = 11 digits total.

Zero-Padding Conversion Rules

Key properties: exactly one leading zero is added in every case; each 10-digit NDC maps to exactly one 11-digit NDC (bijective); the conversion is deterministic only when you know the segment configuration.

Where NDC11 Is Used

HIPAA electronic claims (EDI 837), CMS/Medicare/Medicaid billing systems, pharmacy benefit managers (PBMs), electronic health records (EHR), RxNorm (NLM's normalized drug naming system), and the NSDE (FDA's Comprehensive NDC SPL Data Elements File).

When hyphens are removed from a 10-digit NDC, the resulting 10-character digit string is ambiguous. Without knowing the original segment configuration, you cannot determine where the segment boundaries fall.

Concrete Example

The string 0591036901 (10 digits, no hyphens) can be parsed three ways:

The 6-Digit Labeler Collision (The Breaking Point)

The problem escalates once FDA begins assigning 6-digit labeler codes. A native 11-digit NDC in configuration 6-3-2 would produce the same digit count as the HIPAA 11-digit standard (5-4-2). Without hyphens, these become indistinguishable — identical strings pointing to different drugs. This collision is the primary technical driver for the NDC12 rule.

Industry Mitigations (Current)

1. Always store with hyphens — the hyphenated form is unambiguous
2. Always convert to 11-digit canonical form — the 5-4-2 format is unambiguous
3. Use lookup tables — match whole NDC identifiers against the FDA directory rather than parsing segments algorithmically
4. Never store raw 10-digit without hyphens — this is the only format that is genuinely ambiguous

On Drug Labels (FDA-Regulated)

Per 21 CFR 201.25, the NDC must appear on drug labels as a 10-digit number in one of the three valid configurations, displayed with hyphens between segments. A barcode encoding the NDC must also be present.

In the FDA NDC Directory

In HIPAA/EDI Claims

11-digit, no hyphens, no spaces: 00591036901

Recommended Storage Strategy

Registration Process

1. Establishment Registration: Manufacturer/repacker/relabeler registers facility with FDA via SPL XML through the FDA Gateway. Annual renewal required (October 1 – December 31).
2. Labeler Code Request: New registrant submits SPL type "NDC Labeler Code request" with company name, DUNS number, and contact. FDA reviews and assigns a labeler code (currently always 5 digits, range 10000-99999).
3. Drug Listing: For each product, labeler submits Drug Listing SPL containing: NDC (product and package codes), proprietary and non-proprietary names, dosage form and route of administration, active ingredients (UNII codes) with strengths, application number (if applicable), start marketing date, DEA schedule, all packaging configurations, and label images.
4. Ongoing Updates: Drug listings must be updated twice annually (June and December). Repackers include the Source NDC.

What Gets Published

The NDC Directory is updated daily. Products are excluded from the main download if flagged:

• E — non-compliance
• U — expired certification
• I — FDA-inactivated
• D — discontinued

The Global Trade Item Number (GTIN) is the GS1 standard identifier for trade items worldwide. All GTIN formats share the same logical structure — they differ only in total digit length. Every GTIN ends with a check digit.

Normalization Rule

All GTIN formats are stored in databases as 14-digit strings by left-padding with zeros:

• GTIN-8 → 000000 + 8 digits
• GTIN-12 → 00 + 12 digits
• GTIN-13 → 0 + 13 digits
• GTIN-14 → as-is

This normalization ensures a single field type can hold any GTIN format and enables uniform lookup.

A GTIN-14 is exactly 14 digits, composed of four logical fields:

[Indicator Digit] [GS1 Company Prefix + Item Reference] [Check Digit]
     1 digit                   12 digits                   1 digit

Critical constraint: GS1 Company Prefix + Item Reference always totals
exactly 12 digits. The split between prefix and reference is variable
(6-10 digit prefix, corresponding 6-2 digit reference), but the total is fixed.

Indicator Digit (Position 1)

Position:   1    2  3  4  5  6  7  8  9  10 11 12 13    14
          [IND] [----GS1 Company Prefix----] [--Ref--]  [CD]
                |<--------- 12 digits --------->|

The GS1 standard uses a Modulo-10 algorithm with alternating weights of 3 and 1. This applies to GTIN-8, GTIN-12, GTIN-13, GTIN-14, SSCC, and all other GS1 key identifiers.

Algorithm Steps

1. Write out the first 13 digits (positions 1-13)
2. Assign alternating weights starting with 3 for position 1: 3,1,3,1,3,1,3,1,3,1,3,1,3
3. Multiply each digit by its weight
4. Sum all products
5. Check Digit = (10 - (sum mod 10)) mod 10

Worked Example

GTIN-14 first 13 digits: 0 3 6 1 4 1 4 9 9 9 9 5 1

Sum = 0+3+18+1+12+1+12+9+27+9+27+5+3 = 127

Check digit = (10 − (127 mod 10)) mod 10 = (10 − 7) mod 10 = 3

Full GTIN-14: 03614149999513

Pseudocode

def gs1_check_digit(digits: str) -> int:
    """Calculate GS1 Mod-10 check digit for any GS1 key identifier."""
    total = 0
    for i, d in enumerate(digits):
        weight = 3 if (i % 2 == 0) else 1  # position 1 = index 0 = weight 3
        total += int(d) * weight
    return (10 - (total % 10)) % 10

GS1 US reserved the GS1 Prefix "03" specifically for U.S. FDA NDC Labeler Code holders. This is the bridge between the FDA's NDC system and GS1's global GTIN system.

This is the critical mechanism by which the pharmaceutical supply chain identifies drugs using GS1 barcodes while maintaining traceability back to the FDA NDC.

The General Formula

GTIN-14 = [Indicator] + "03" + [10-digit NDC] + [Check Digit]
         = [1 digit]  + [2]  + [10 digits]    + [1 digit]
         = 14 digits

Where:
  Indicator   = 0 for unit-of-use, 1-8 for groupings (case, pallet)
  "03"        = GS1 prefix for FDA labelers
  NDC10       = all 10 digits without hyphens, in original segment order
  Check Digit = GS1 Mod-10 calculated over positions 1-13

Concrete Example

Drug: NDC10 0409-4921-34 (4-4-2), indicator digit = 1 (case level)

Positions 1-13: 1 0 3 0 4 0 9 4 9 2 1 3 4
Check digit:   8
GTIN-14:       10304094921348

GTIN-14 for 5-digit Labeler (5-3-2)

Position:   1    2   3    4   5   6   7   8    9  10  11  12  13    14
          [IND] [0] [3]  [L] [L] [L] [L] [L]  [P] [P] [P] [K] [K]  [CD]
           (0)       "03" prefix    5-digit       3-digit    2-digit
                                    labeler       product    package

GTIN-14 for 4-digit Labeler (4-4-2)

Position:   1    2   3    4   5   6   7    8   9  10  11   12  13    14
          [IND] [0] [3]  [L] [L] [L] [L]  [P] [P] [P] [P]  [K] [K]  [CD]
           (0)       "03" prefix   4-digit      4-digit       2-digit
                                   labeler      product       package

From GTIN-14

GTIN-14:  0  0  3  L  L  L  L  L  P  P  P  K  K  CD
          ^  ^  ^                                  ^
          |  |  |                                  |
          |  +--+-- strip "03" prefix              +-- strip check digit
          +-- strip indicator

NDC10 = positions 4-13 (10 digits, no hyphens)

From GTIN-12 (UPC-A)

GTIN-12:  0  3  L  L  L  L  L  P  P  P  K  CD
          ^  ^                             ^
          +--+-- strip "03"                +-- strip check digit

NDC = positions 3-11 (9-10 digits depending on config)

The Drug Supply Chain Security Act (Title II of FDASIA, signed November 2013, codified at 21 U.S.C. 360eee et seq.) established a phased U.S. electronic track-and-trace system for prescription drugs.

Product Identifier (PI) — Four Required Elements

Machine-Readable Format: GS1 2D DataMatrix

DSCSA Implementation Timeline

The New NDC12 Format: Uniform 6-4-2

Display format with hyphens: LLLLLL-PPPP-KK (e.g., 000591-0369-01)

Why the Change Was Necessary

1. Labeler code exhaustion: 5-digit labeler codes (range 10000-99999) will be exhausted within ~10-15 years. 6-digit codes provide ~900,000 additional codes.
2. Format ambiguity elimination: The variable 4-4-2 / 5-3-2 / 5-4-1 configurations make unhyphenated 10-digit NDCs ambiguous. A single 6-4-2 format eliminates all parsing ambiguity.
3. Collision prevention: With 6-digit labelers, native 11-digit NDCs (e.g., 6-3-2 = 11 digits) would collide with HIPAA 11-digit NDCs (5-4-2 = 11 digits) when hyphens are stripped.
4. International alignment: A single fixed-length format reduces impedance mismatch between FDA labeling, HIPAA claims, and GS1 supply chain systems.

Conversion of Existing NDCs

HIPAA Gap

FDA's authority does not extend to HIPAA transaction standards. CMS will need to separately update the 11-digit HIPAA NDC billing standard to accept 12 digits. This requires separate HHS/CMS rulemaking.

Rulemaking History

This is the most technically disruptive aspect of the NDC12 transition.

The Fundamental Problem

Under the current system:
GTIN-14 = [1 indicator] + "03" + [10-digit NDC] + [1 check digit] = 14 digits  ✓

With NDC12:
GTIN-14 = [1 indicator] + "03" + [12-digit NDC] + [1 check digit] = 16 digits  ✗ OVERFLOW

Two Classes of Products (Post-2033)

For legacy products (existing NDC10s converted to NDC12 via leading zeros), the original GTIN remains valid because the embedded 10-digit NDC hasn't changed — only the FDA's representation of it has gained leading zeros.

GS1 US developed a new Application Identifier (AI) 715 specifically for carrying a 12-digit NDC as a separate data element alongside the GTIN in GS1 barcodes.

Old vs. New Barcode Model

Old model (current):
  (01) GTIN-14          <-- NDC is embedded inside the GTIN
  (21) Serial
  (10) Lot
  (17) Expiry

New model (post-2033, new NDC12 products):
  (01) GTIN-14          <-- GTIN assigned independently, no NDC embedded
  (715) NDC12           <-- NDC carried as separate data element
  (21) Serial
  (10) Lot
  (17) Expiry

Processing Logic

1. Read the GTIN from AI (01)
2. Read the NDC from AI (715) — if present
3. If AI (715) is absent, extract the NDC from the GTIN using the legacy "03" extraction method
4. Cross-reference against master data to validate the GTIN/NDC association

Barcode Carrier Capabilities

Impact on Existing Serialized Products

When existing NDCs are converted to NDC12 via leading zeros, the 10-digit NDC embedded in the GTIN does not change. The GTIN itself remains valid. Existing serialized product in the supply chain is not affected by the format change alone.

Impact on New Products (NDC12 Assigned from 2033)

New products assigned 12-digit NDCs from 2033 cannot have their NDC embedded in the GTIN. Their barcodes will use the AI 715 model.

Serialization Platform Requirements

1. Generate both legacy (NDC-embedded GTIN) and new (GTIN + AI 715) barcode formats
2. Read/interpret AI 715 in incoming barcode scans
3. Maintain GTIN-to-NDC association in master data for both paradigms
4. Verify product identifiers using the correct extraction method based on whether AI 715 is present
5. Report to FDA using NDC12 format regardless of barcode encoding method

Convergence Benefit

Post-2033, a single 2D DataMatrix encoding AI (01) + AI (715) + AI (21) + AI (10) + AI (17) can satisfy both 21 CFR 201.25 labeling requirements and DSCSA requirements simultaneously, eliminating the need for dual barcodes on pharmaceutical labels.

Key Dates Summary

Database Schema Considerations

SQL Conversion Logic

-- From NDC11 (5-4-2) to NDC12 (6-4-2): add 1 leading zero to labeler
-- NDC11: LLLLL-PPPP-KK (11 digits)
-- NDC12: 0LLLLL-PPPP-KK (12 digits)
SELECT '0' || NDC11_PACKAGE AS NDC12_PACKAGE,
       '0' || SUBSTR(NDC11_PACKAGE_DISP, 1, 5) || SUBSTR(NDC11_PACKAGE_DISP, 6) AS NDC12_PACKAGE_DISP
FROM NDC_PACKAGE;

-- Note: This simple prepend works because the NDC11 5-4-2 format already has
-- the product and package segments at their target 4-2 lengths.
-- Only the labeler segment needs one more leading zero (5 -> 6).

GTIN Processing Logic (Future)

Input: Barcode scan data
IF AI (715) present:
    NDC12 = AI (715) value
    GTIN = AI (01) value
    # NDC is NOT derived from GTIN
ELSE:
    GTIN = AI (01) value
    NDC10 = extract from GTIN (positions 4-13, strip "03")
    NDC11 = zero-pad to 5-4-2
    NDC12 = zero-pad to 6-4-2

Timeline for System Changes

All NDC Formats at a Glance

NDC-to-GTIN Mapping

GS1 Application Identifiers for Pharma

Barcode Carrier Capabilities