R51.9 — Headache, unspecified
Is R51.9 billable?
Yes, but R51.9 is an unspecified code. R51.9 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, R51.9 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting R51.9 — the more specific alternatives are listed below.
More specific alternatives
R51.9 at a glance
| Code | R51.9 |
|---|---|
| Description | Headache, unspecified |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does R51.9 group to?
R51.9 sits in MDC 01 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 102Headaches with MCCmedical
- 103Headaches without MCCmedical
How is R51.9 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to R51.9. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Headache
- Headache › chronic daily
- Headache › daily chronic
- Headache › nasal septum
- Pain › face, facial (s)
Inclusion terms
Alternative wording in documentation that is classified to R51.9.
- Facial pain NOS
Excludes2 — not included here — inherited from Chapter 18
The conditions below are not part of R51.9, but a patient may have both at the same time. When documentation supports it, R51.9 and the excluded code may both be reported.
Excludes2 — not included here — inherited from R51
The conditions below are not part of R51.9, but a patient may have both at the same time. When documentation supports it, R51.9 and the excluded code may both be reported.
How long has R51.9 existed?
R51.9 first appears in FY2021 (FY2020 is not available, so it may have appeared then).
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with R51.9?
ICD-10-CM declares these codes mutually exclusive with R51.9 — exactly one of each pair can be correct for a given encounter.