The NDC is a unique 10-digit, 3-segment number assigned to each medication listed under Section 510 of the U.S. Federal Food, Drug, and Cosmetic Act. The number identifies the labeler or vendor, product, and trade package size:
The product and package codes are assigned by the firm.
According to the FDA, the NDC may be in one of the following configurations: 4-4-2, 5-3-2, or 5-4-1. An asterisk may appear in either a product code or a package code. It simply acts as a place holder and indicates the configuration of the NDC.
Since the NDC is limited to 10 digits, a firm with a 5 digit labeler code must choose between a 3 digit product code and 2 digit package code, or a 4 digit product code and 1 digit package code. Thus, you have either a 5-4-1 or a 5-3-2 configuration for the three segments of the NDC.
Because of a conflict with the HIPAA standard of an 11 digit NDC, many programs will pad the product code or package code segments of the NDC with a leading zero instead of the asterisk. Since a zero can be a valid digit in the NDC, this can lead to confusion when trying to reconstitute the NDC back to its FDA standard. Examples of NDC numbers which represent different products:
Correctly padding the appropriate section with a leading zero yields an unambiguous standard 5-4-2 format:
Code 128 is a continuous, variable-length, high-density symbology which permits the encoding of alphanumeric data. The symbology encodes the full ASCII 128 character set, and includes a checksum digit for verification. Code 128 has been widely implemented in many applications where a relatively large amount of data must be encoded in a relatively small amount of space.
Every Code 128 character has 3 bars and 3 spaces comprising a total of 11 modules. Each bar or space can be one, two, three, or four modules wide. The Code 128 specification defines three character subsets or modes:
A Code 128 bar code consists of a leading quiet zone, one of three start codes, the data itself, a check character, a stop character, and a trailing quiet zone.
The start code that is used determines which character set will be used. The character set may also be changed in the middle of the bar code. The switch code changes the subset for the next character only. To create a more compact NDC, character set "C" is used because of it's double density. For an 11-digit NDC, start with character set "C" for the first 10 digits, then switch to subset "B" for the final digit.
To encode a value as a Code 128 bar code, the checksum digit must first be calculated (see procedure below) and the entire bar code, including check digit, may then be encoded as a sequence of bars and spaces.
A Code 128 bar code for an 11-digit NDC has the following physical structure:
An example of a Code 128 bar code for Fosinopril 10mg, NDC 00185-0041-09:
Before a Code 128 symbol may be encoded, the checksum digit to be included in the barcode must be calculated. The checksum digit is based on a modulo 103 calculation based on the weighted sum of the values of each of the digits in the message that is being encoded, including the start character.
The steps for calculating the check digit are as follows:
This is easier to understand with an example. Let's calculate the checksum digit for the sample bar code above, Fosinopril 10mg, NDC "00185-0041-09".
Barcode | START-C | 00 | 18 | 50 | 04 | 10 | SWITCH-B | 9 |
Character Value | 105 | 00 | 18 | 50 | 04 | 10 | 100 | 25 value for set B is number + 16 |
Character Position | - | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
Calculation | 105 | 00 x 1 | 18 x 2 | 50 x 3 | 04 x 4 | 10 x 5 | 100 x 6 | 25 * 7 |
Weighted Sum | 105 | 0 | 36 | 150 | 16 | 50 | 600 | 175 |
Running sum | 105 | 105 | 141 | 291 | 307 | 350 | 957 | 1132 |
Summing up the running checksum for each digit, we get 1132. This value divided by 103 is 1132 / 103 = 10 with a remainder of 102. Thus the checksum digit is the character which has a value of 102.
Once the checksum digit has been calculated we know the entire message which must be encoded in the bars and spaces. Continuing with our example, we will encode, from zero, the Code 128 bar code we used in our example above: 00185004109 with a checksum digit of 102.
The encoding table at the bottom of this page indicates how to encode each digit of a Code 128 barcode. The number "1" represents a "dark" or "bar" section of the bar code whereas a "0" represents a "light" or "space" section of the bar code. Thus the numbers 1101 represents a double-wide bar (11), followed by a single-wide space (0), followed by a single-wide bar (1). This would be printed in the bar code as:
We will now code the above NDC example, 00185-0041-09, in Code 128. As we calculated in the Checksum Digit Calculation section, the checksum digit is 102. So we must also code the checksum digit at the end of the message.
We encode each digit using the encoding table below.
This is shown in the following graphical representation where the bar code has been sectioned-off into areas that reflect each of the 11 components described above.
This table indicates how to encode each digit of a Code 128 bar code. Note that it is easiest to think of each character as a value between 0 and 105, inclusive, rather than thinking of them as characters. The character that a value represents depends on what mode (or character set) you're in-so rather than thinking of a character as "A" or "B", etc. it is more appropriate to think of it as 33, 34, etc.
VALUE | WHICH REPRESENTS IN CHARACTER SET |
ENCODING | VALUE | WHICH REPRESENTS IN CHARACTER SET |
ENCODING | ||||
A | B | C | A | B | C | ||||
00 | SP | SP | 00 | 11011001100 | 53 | U | U | 53 | 11011101110 |
01 | ! | ! | 01 | 11001101100 | 54 | V | V | 54 | 11101011000 |
02 | " | " | 02 | 11001100110 | 55 | W | W | 55 | 11101000110 |
03 | # | # | 03 | 10010011000 | 56 | X | X | 56 | 11100010110 |
04 | $ | $ | 04 | 10010001100 | 57 | Y | Y | 57 | 11101101000 |
05 | % | % | 05 | 10001001100 | 58 | Z | Z | 58 | 11101100010 |
06 | & | & | 06 | 10011001000 | 59 | [ | [ | 59 | 11100011010 |
07 | ' | ' | 07 | 10011000100 | 60 | \ | \ | 60 | 11101111010 |
08 | ( | ( | 08 | 10001100100 | 61 | ] | ] | 61 | 11001000010 |
09 | ) | ) | 09 | 11001001000 | 62 | ^ | ^ | 62 | 11110001010 |
10 | * | * | 10 | 11001000100 | 63 | _ | _ | 63 | 10100110000 |
11 | + | + | 11 | 11000100100 | 64 | NUL | ` | 64 | 10100001100 |
12 | , | , | 12 | 10110011100 | 65 | SOH | a | 65 | 10010110000 |
13 | - | - | 13 | 10011011100 | 66 | STX | b | 66 | 10010000110 |
14 | . | . | 14 | 10011001110 | 67 | ETX | c | 67 | 10000101100 |
15 | / | / | 15 | 10111001100 | 68 | EOT | d | 68 | 10000100110 |
16 | 0 | 0 | 16 | 10011101100 | 69 | ENQ | e | 69 | 10110010000 |
17 | 1 | 1 | 17 | 10011100110 | 70 | ACK | f | 70 | 10110000100 |
18 | 2 | 2 | 18 | 11001110010 | 71 | BEL | g | 71 | 10011010000 |
19 | 3 | 3 | 19 | 11001011100 | 72 | BS | h | 72 | 10011000010 |
20 | 4 | 4 | 20 | 11001001110 | 73 | HT | i | 73 | 10000110100 |
21 | 5 | 5 | 21 | 11011100100 | 74 | LF | j | 74 | 10000110010 |
22 | 6 | 6 | 22 | 11001110100 | 75 | VT | k | 75 | 11000010010 |
23 | 7 | 7 | 23 | 11101101110 | 76 | FF | l | 76 | 11001010000 |
24 | 8 | 8 | 24 | 11101001100 | 77 | CR | m | 77 | 11110111010 |
25 | 9 | 9 | 25 | 11100101100 | 78 | SO | n | 78 | 11000010100 |
26 | : | : | 26 | 11100100110 | 79 | SI | o | 79 | 10001111010 |
27 | ; | ; | 27 | 11101100100 | 80 | DLE | p | 80 | 10100111100 |
28 | < | < | 28 | 11100110100 | 81 | DC1 | q | 81 | 10010111100 |
29 | = | = | 29 | 11100110010 | 82 | DC2 | r | 82 | 10010011110 |
30 | > | > | 30 | 11011011000 | 83 | DC3 | s | 83 | 10111100100 |
31 | ? | ? | 31 | 11011000110 | 84 | DC4 | t | 84 | 10011110100 |
32 | @ | @ | 32 | 11000110110 | 85 | NAK | u | 85 | 10011110010 |
33 | A | A | 33 | 10100011000 | 86 | SYN | v | 86 | 11110100100 |
34 | B | B | 34 | 10001011000 | 87 | ETB | w | 87 | 11110010100 |
35 | C | C | 35 | 10001000110 | 88 | CAN | x | 88 | 11110010010 |
36 | D | D | 36 | 10110001000 | 89 | EM | y | 89 | 11011011110 |
37 | E | E | 37 | 10001101000 | 90 | SUB | z | 90 | 11011110110 |
38 | F | F | 38 | 10001100010 | 91 | ESC | { | 91 | 11110110110 |
39 | G | G | 39 | 11010001000 | 92 | FS | | | 92 | 10101111000 |
40 | H | H | 40 | 11000101000 | 93 | GS | } | 93 | 10100011110 |
41 | I | I | 41 | 11000100010 | 94 | RS | ~ | 94 | 10001011110 |
42 | J | J | 42 | 10110111000 | 95 | US | DEL | 95 | 10111101000 |
43 | K | K | 43 | 10110001110 | 96 | FNC3 | FNC3 | 96 | 10111100010 |
44 | L | L | 44 | 10001101110 | 97 | FNC2 | FNC2 | 97 | 11110101000 |
45 | M | M | 45 | 10111011000 | 98 | SHIFT | SHIFT | 98 | 11110100010 |
46 | N | N | 46 | 10111000110 | 99 | Code C | Code C | 99 | 10111011110 |
47 | O | O | 47 | 10001110110 | 100 | Code B | FNC4 | Code B | 10111101110 |
48 | P | P | 48 | 11101110110 | 101 | FNC4 | Code A | Code A | 11101011110 |
49 | Q | Q | 49 | 11010001110 | 102 | FNC1 | FNC1 | FNC1 | 11110101110 |
50 | R | R | 50 | 11000101110 | 103 | START A | START A | START A | 11010000100 |
51 | S | S | 51 | 11011101000 | 104 | START B | START B | START B | 11010010000 |
52 | T | T | 52 | 11011100010 | 105 | START C | START C | START C | 11010011100 |
STOP | STOP | STOP | 11000111010 |