1. Convert a 10-digit NDC to 11 digits
2. Turn the dose into HCPCS billing units
3. Build the NDC line for the claim
How the NDC 10 to 11 Digit Conversion Works
Drug packages show a 10-digit NDC in one of three formats. Claims need 11 digits in a 5-4-2 format, so you add a leading zero to the short segment.
| Package format | Example | Add a zero | 11-digit result |
|---|---|---|---|
| 4-4-2 | 0409-4888-02 | At the start of the first segment | 00409-4888-02 |
| 5-3-2 | 63323-262-01 | At the start of the middle segment | 63323-0262-01 |
| 5-4-1 | 12345-6789-1 | At the start of the last segment | 12345-6789-01 |
On the claim, leave out the dashes: 00409488802.
HCPCS Units vs NDC Units
HCPCS units come from the dose in the code description. NDC units describe how much of the actual package you used. They are often different numbers on the same claim line.
| Code | Billing unit | Dose given | HCPCS units |
|---|---|---|---|
| J0696 (ceftriaxone) | per 250 mg | 1 g (1,000 mg) | 4 |
| J1885 (ketorolac) | per 15 mg | 30 mg | 2 |
| J1100 (dexamethasone) | 1 mg | 10 mg | 10 |
| J3420 (vitamin B-12) | up to 1,000 mcg | 1,000 mcg | 1 |
| J0585 (onabotulinumtoxinA) | 1 unit | 100 units | 100 |
| J2405 (ondansetron) | per 1 mg | 4 mg | 4 |
If the dose falls between two unit amounts, most payers want you to round up to the next whole unit. Check your payer's rule. Look up any drug code's unit in our HCPCS code lookup.
JW and JZ: Reporting Drug Waste
- JW: when part of a single-dose vial is thrown away, report the discarded amount on its own line with modifier JW.
- JZ: Medicare requires JZ on the drug line when none of a single-dose container was thrown away.
- Neither applies to multi-dose vials.
- Write the amount given and the amount discarded in the record.
Where the NDC Goes on the Claim
On the CMS-1500, put the NDC line in the shaded part of box 24A: the qualifier N4, the 11-digit NDC with no dashes, the unit of measure and the quantity. For example: N400409488802ML2. On an electronic 837P claim, the NDC goes in loop 2410 (segments LIN and CTP).
| Unit code | Use it for |
|---|---|
| ML | Liquids measured in milliliters |
| UN | Each, such as a vial, tablet or kit |
| GR | Grams, such as creams |
| F2 | International units |
| ME | Milligrams |
Common NDC Billing Errors
- A 10-digit NDC, or an 11-digit one with the zero in the wrong place.
- HCPCS units based on the vial size instead of the dose given.
- An NDC that does not match the drug in the HCPCS code.
- Missing JW or JZ on single-dose drugs billed to Medicare.
- Units over the daily limit. Check them in the MUE lookup.
Frequently Asked Questions
Written by Hassan Raza Awan
Founder — LegitMedBilling & IT Solutions
Hassan has 4+ years of hands-on U.S. medical billing experience — working claims, denials, credentialing, and payer follow-up for practices across the United States. Every guide he publishes is written from real remittances and payer behavior, not theory.
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