# Regular expressions for HCPCS codes

> Source: <https://www.johndcook.com/blog/2026/07/17/regular-expressions-for-hcpcs-codes/>
> Published: 2026-07-17 14:02:52+00:00

Since I revisited my old post on ICD code matching, I thought I’d revisit by [post on HCPCS codes](https://www.johndcook.com/blog/2022/09/23/hcpcs-codes/) too.

HCPCS stands for Healthcare Common Procedure Coding System, and is pronounced “hick picks.” When most people say HCPCS, they technically mean HCPCS Level II, and that’s what I mean here.

The format of a HCPCS code is simple: one letter and four digits. In regex terms,

```
    [A-Z]\d{4}
```

Not all letters are used, so you can get more specific and say

```
    [A-CEGHJ-MP-V][0-9]\d{4}
```

Some sources say no codes begin with U, but there are currently five codes that begin with U.

When I was doing some research on HCPCS codes recently using AI, I was told there is a D code for dentistry, but that was a hallucination.

HCPCS codes can also have modifiers. These consist of a letter and either a letter or digit:

```
    [A-Z][A-Z0-9]
```

Not all letters actually appear in modifiers—I, O, W, and Y are missing—so you could be more specific. At the time of writing there are 384 official modifiers.

Modifiers are often stored in a separate column in a database, but in text you’ll see a HCPCS code optionally followed by a dash and a modifier. So a regex to match HCPCS codes with possible modifiers would be

```
    [A-CEGHJ-MP-V][0-9]\d{4}(-[A-Z][A-Z0-9])?
```

This regex will have some false positives, but it should not have false negatives: every real HCPCS code should match.

Of course you could search against a complete list of HCPCS codes. This would be more accurate and slower. I did a test similar to the one in the [previous post](https://www.johndcook.com/blog/2026/07/17/regex-speed-error/) and found a search with the regex above took 20 milliseconds, while a search against the list of HCPCS codes took 46 seconds.

However, the regex searched for possible modifiers and the exhaustive search only looked for unmodified HCPCS codes. A complete list of HCPCS codes with possible modifiers would be tedious to create because some combinations of codes and modifiers make no sense. And I imagine that some combinations that would make sense are not used in practice.