# Claim edit: Invalid drug unit count

> Stedi now rejects 837P professional and 837I institutional claims that bill for a drug or biologic without a valid unit count.

Published Dec 10, 2025

Product: Claim edits

Stedi now rejects [837P professional](https://www.stedi.com/docs/healthcare/submit-professional-claims) and [837I institutional](https://www.stedi.com/docs/healthcare/submit-institutional-claims) claims that bill for a drug or biologic without a valid unit count.

In professional and institutional claims, you bill for drugs or biologics by adding information about the drug to a service line, specifying what drug was administered and how much.

The line’s unit of measurement code – such as `F2` (International Unit) or `GR` (Gram) – shows how the drug was measured. The line’s unit count reports the quantity administered in that measure.

Payers use the measurement code and unit count to verify dosage and pricing. Without a valid unit count, they can’t confirm the billed amount and may reject the claim, which can delay payment.

This edit – the industry’s term for an automated validation rule – catches the issue before it reaches the payer.

**When this edit applies**  
A professional or institutional claim will fail this edit in the following cases:

- **JSON API**  
  If you’re using one of Stedi’s [JSON claim submission API endpoints](https://www.stedi.com/docs/healthcare/intro-to-claim-submission#api-claim-submission), the edit fails if:

  - A service line contains a `drugIdentification.measurementUnitCode` value.  
    AND

  - The service line’s `drugIdentification.nationalDrugUnitCount` field is less than or equal to `”0”`.

- **Raw X12**  
  If you’re using raw X12, the edit fails if:

  - `Loop 2410` (Drug Identification) is present  
    AND

  - The `CTP-05` (Composite Unit of Measure) of `Loop 2410` contains a value.  
    AND

  - The `CTP-04` (National Drug Unit Count)  of `Loop 2410`  is less than or equal to `0`.

- **Stedi portal**  
  If you’re using the Stedi portal’s [professional claim form](https://www.stedi.com/docs/providers/providers-submit-claims), the edit fails if:

  - **Box 24 – Service Lines** contains a service line with a **Unit/Basis of measurement** value and a **Quantity** less than or equal to zero.

    Unit/Basis of measurement value with a Quantity less than or equal to zero.

**Rejection errors**  
If you submit a claim that fails the edit using Stedi’s [claim submission APIs](https://www.stedi.com/docs/healthcare/intro-to-claim-submission#api-claim-submission) or [professional claim form](https://www.stedi.com/docs/providers/providers-submit-claims), you’ll get back an error message in real time. If you’re using a JSON API endpoint, the response includes error details in the `errors` array:

```jsonc
{
  "errors": [
    {
      "code": "33",
      "description": "Invalid drug unit count. When reporting a drug unit qualifier, the drug count must be greater than zero (0.0). Correct and resubmit.",
      "followupAction": "Please Correct and Resubmit"
    }
  ]
}
```

If you submit a claim that fails the edit using SFTP, Stedi will reject the claim with a [277CA claim acknowledgment](https://www.stedi.com/docs/healthcare/claim-responses-overview#277ca-claim-acknowledgment). The acknowledgment will contain a related claim status category code, claim status code, and error message. You can use the error message to correct and resubmit the claim.