# Code with ancestors and children

URL: https://docs.healthcare.dev/reference/codes/code-with-ancestors-and-children

```http
GET https://api.healthcare.dev/v1/codes/{system}/{code}/hierarchy
```

The code, its ancestors (root first) and its direct active children in one call.

Requires an API key: `Authorization: Bearer hdev_live_...`. See [Authentication](/authentication).

## Path parameters

| Name | Type | Required | Description | Example |
| --- | --- | --- | --- | --- |
| `system` | "icd10cm" \| "icd10pcs" \| "hcpcs" | yes | Code system | `icd10cm` |
| `code` | string | yes | Code, with or without the dot | `E11.9` |

## Query parameters

| Name | Type | Required | Description | Example |
| --- | --- | --- | --- | --- |
| `view` | "compact" \| "full" | no | `compact` returns only the fields an agent usually needs (fewer tokens); `full` (default) returns every field | `compact` |
| `fields` | string | no | Comma-separated record fields to return, e.g. `code,display,billable` | `code,display,billable` |

## Examples

**curl**

```sh
curl "https://api.healthcare.dev/v1/codes/icd10cm/E11.9/hierarchy" \
  -H "Authorization: Bearer $HDEV_API_KEY"
```

**TypeScript**

```ts
const res = await fetch("https://api.healthcare.dev/v1/codes/icd10cm/E11.9/hierarchy", {
  headers: { Authorization: `Bearer ${process.env.HDEV_API_KEY}` },
});
const { data, meta } = await res.json();
```

**Python**

```python
import os
import requests

res = requests.get("https://api.healthcare.dev/v1/codes/icd10cm/E11.9/hierarchy", headers={"Authorization": f"Bearer {os.environ['HDEV_API_KEY']}"})
body = res.json()
```

## Response

Hierarchy

```json
{
  "data": {
    "parents": [
      {
        "system": "icd10cm",
        "code": "E11.9",
        "display": "Type 2 diabetes mellitus without complications",
        "description": "Type 2 diabetes mellitus without complications",
        "billable": true,
        "parent": "E11",
        "attributes": {},
        "status": "active",
        "effective_start": "2015-10-01",
        "effective_end": null,
        "replaced_by": []
      }
    ],
    "code": {
      "system": "icd10cm",
      "code": "E11.9",
      "display": "Type 2 diabetes mellitus without complications",
      "description": "Type 2 diabetes mellitus without complications",
      "billable": true,
      "parent": "E11",
      "attributes": {},
      "status": "active",
      "effective_start": "2015-10-01",
      "effective_end": null,
      "replaced_by": []
    },
    "children": [
      {
        "system": "icd10cm",
        "code": "E11.9",
        "display": "Type 2 diabetes mellitus without complications",
        "description": "Type 2 diabetes mellitus without complications",
        "billable": true,
        "parent": "E11",
        "attributes": {},
        "status": "active",
        "effective_start": "2015-10-01",
        "effective_end": null,
        "replaced_by": []
      }
    ]
  },
  "meta": {
    "source": "cms-icd10",
    "data_version": "2026.1",
    "retrieved_at": "2026-10-24T12:00:00Z",
    "license": "Public domain (CMS). Reference data, not medical advice."
  },
  "links": {
    "self": "/v1/codes/icd10cm/E11.9/hierarchy",
    "next": null
  }
}
```

### Fields

| Field | Type | Always present | Description |
| --- | --- | --- | --- |
| `parents` | Code[] | yes |  |
| `code` | Code | yes |  |
| `children` | Code[] | yes |  |

## Errors

Errors are `application/problem+json` ([RFC 9457](https://www.rfc-editor.org/rfc/rfc9457)). Branch on `type`, not on `title`. See [Errors](/errors).

| Status | `type` | When |
| --- | --- | --- |
| 400 | `invalid-request` | A parameter or the body failed validation; `errors` lists each field. |
| 401 | `unauthorized` | Missing, malformed or revoked API key. |
| 404 | `not-found` | No record with that id (retired records are still returned). |
| 429 | `rate-limited / quota-exceeded` | Too many requests per second (retry after `Retry-After`), or the monthly quota is used up. |
| 503 | `dataset-unavailable / unavailable` | The dataset has no published version yet, or the service is degraded. |