# NLM Clinical Tables API

> NLM Clinical Tables returns ICD-10-CM diagnosis codes and details as a workflow and API.

NLM Clinical Tables finds ICD-10-CM codes and official names from a plain-language condition description, with an optional result maximum. Explain diagnosis code returns an official name, category, chapter, and billable status for a supplied ICD-10-CM code, with or without a dot.

- Page: https://fous.com/tools/nlm-clinical-tables
- Handle: `@nlm-clinical-tables`
- Category: [Health](https://fous.com/tools/category/health)
- Source website: https://clinicaltables.nlm.nih.gov
- Last verified: Oct 7, 2026

## Methods

### Explain diagnosis code

Operation `explain_diagnosis_code`, version 1. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.

Explain an ICD-10-CM diagnosis code with its official name, category, chapter, and whether it is billable. Codes are checked against the current NLM table and the corresponding official classification.

**Input**

| Field | Type | Required | Example | Description |
|---|---|---|---|---|
| `code` | string | yes | `"E119"` | ICD-10-CM diagnosis code as printed, with or without the dot (for example, E11.9 or E119). |

**Input schema**

```json
{
  "type": "object",
  "required": [
    "code"
  ],
  "properties": {
    "code": {
      "type": "string",
      "description": "ICD-10-CM diagnosis code as printed, with or without the dot (for example, E11.9 or E119).",
      "examples": [
        "E119",
        "B20",
        "E11"
      ]
    }
  },
  "additionalProperties": false,
  "examples": [
    {
      "code": "E119"
    },
    {
      "code": "B20"
    },
    {
      "code": "E11"
    }
  ]
}
```

**Output**

| Field | Type | Example | Description |
|---|---|---|---|
| `code` | string | `"E11.9"` | Diagnosis code with a dot after the first three characters. |
| `chapter` | string | `"Endocrine, nutritional and metabolic diseases"` | ICD-10-CM chapter name in words. |
| `billable` | boolean | `true` | Whether the code is sufficiently specific to bill. |
| `page_url` | string | `"https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=E11.9&sf=code"` | Link to the code in the NLM Clinical Tables search. |
| `category_code` | string | `"E11"` | Three-character ICD-10-CM category code. |
| `category_name` | string | `"Type 2 diabetes mellitus"` | Official three-character category name. |
| `official_name` | string | `"Type 2 diabetes mellitus without complications"` | Official diagnosis name. |

**Example input**

```json
{
  "code": "E119"
}
```

**Example output**

```json
{
  "code": "E11.9",
  "chapter": "Endocrine, nutritional and metabolic diseases",
  "billable": true,
  "page_url": "https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=E11.9&sf=code",
  "category_code": "E11",
  "category_name": "Type 2 diabetes mellitus",
  "official_name": "Type 2 diabetes mellitus without complications"
}
```

### Search diagnosis codes

Operation `search_diagnosis_codes`, version 1. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.

Find ICD-10-CM diagnosis codes and official names from a plain-language condition description. Results follow the source search order; broad or unfamiliar wording may not match every relevant code.

**Input**

| Field | Type | Required | Example | Description |
|---|---|---|---|---|
| `description` | string | yes | `"asthma"` | Condition in plain words, such as "type 2 diabetes with kidney problems". |
| `max_results` | integer | no | `3` | Maximum number of matching codes to return, such as 10 (up to 50). |

**Input schema**

```json
{
  "type": "object",
  "required": [
    "description"
  ],
  "properties": {
    "description": {
      "type": "string",
      "minLength": 1,
      "description": "Condition in plain words, such as \"type 2 diabetes with kidney problems\".",
      "examples": [
        "asthma",
        "type 2 diabetes with kidney problems",
        "zyxqw impossible diagnosis"
      ]
    },
    "max_results": {
      "type": "integer",
      "default": 10,
      "maximum": 50,
      "minimum": 1,
      "description": "Maximum number of matching codes to return, such as 10 (up to 50).",
      "x-fous-developer": true,
      "examples": [
        3,
        50
      ]
    }
  },
  "additionalProperties": false,
  "examples": [
    {
      "description": "asthma",
      "max_results": 3
    },
    {
      "description": "type 2 diabetes with kidney problems"
    },
    {
      "description": "zyxqw impossible diagnosis"
    }
  ]
}
```

**Output**

| Field | Type | Example | Description |
|---|---|---|---|
| `diagnosis_codes` | array |  | Matching ICD-10-CM diagnosis codes, best match first. |
| `diagnosis_codes[].code` | string | `"J45.998"` | ICD-10-CM diagnosis code used on forms. |
| `diagnosis_codes[].page_url` | string | `"https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=J45.998&sf=code&df=code%2Cname&count=1"` | NLM record lookup link for this code. |
| `diagnosis_codes[].official_name` | string | `"Other asthma"` | Official ICD-10-CM diagnosis name. |

**Example input**

```json
{
  "description": "asthma",
  "max_results": 3
}
```

**Example output**

```json
{
  "diagnosis_codes": [
    {
      "code": "J45.998",
      "page_url": "https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=J45.998&sf=code&df=code%2Cname&count=1",
      "official_name": "Other asthma"
    },
    {
      "code": "J82.83",
      "page_url": "https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=J82.83&sf=code&df=code%2Cname&count=1",
      "official_name": "Eosinophilic asthma"
    },
    {
      "code": "J45.909",
      "page_url": "https://clinicaltables.nlm.nih.gov/api/icd10cm/v3/search?terms=J45.909&sf=code&df=code%2Cname&count=1",
      "official_name": "Unspecified asthma, uncomplicated"
    }
  ]
}
```

## Quick start

Replace `YOUR_API_KEY` with a Fous API key. To create one, open Developers at the bottom of Fous Studio, turn on Developer mode, then go to API keys (https://app.fous.com/keys). Change the values in `input` to run the same tool on new data.

```bash
curl 'https://api.fous.com/v1/query' \
  --fail-with-body --silent --show-error --max-time 180 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H 'Content-Type: application/json' \
  --data-raw '{
  "api": "@nlm-clinical-tables",
  "visibility": "public",
  "operation": "explain_diagnosis_code",
  "version": 1,
  "input": {
    "code": "E119"
  },
  "response": {
    "format": "json"
  }
}'
```

```python
# Save as fous.py and run with python3 fous.py. No packages needed.
import json
import urllib.error
import urllib.request

api_key = "YOUR_API_KEY"

body = json.loads("{\n  \"api\": \"@nlm-clinical-tables\",\n  \"visibility\": \"public\",\n  \"operation\": \"explain_diagnosis_code\",\n  \"version\": 1,\n  \"input\": {\n    \"code\": \"E119\"\n  },\n  \"response\": {\n    \"format\": \"json\"\n  }\n}")
request = urllib.request.Request(
    "https://api.fous.com/v1/query",
    data=json.dumps(body).encode("utf-8"),
    headers={
        "Authorization": f"Bearer {api_key}",
        "Content-Type": "application/json",
    },
    method="POST",
)
try:
    with urllib.request.urlopen(request, timeout=180) as response:
        result = json.load(response)
except urllib.error.HTTPError as error:
    raise RuntimeError(f"HTTP {error.code}: {error.read().decode('utf-8', errors='replace')}") from error
if result.get("success") is False:
    raise RuntimeError(result.get("error", {}).get("message", "Request failed"))
print(json.dumps(result["data"]["output"], indent=2))
```

```typescript
// Save as fous.mts and run with npx tsx fous.mts.
const apiKey = "YOUR_API_KEY";

const response = await fetch("https://api.fous.com/v1/query", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${apiKey}`,
    "Content-Type": "application/json",
  },
  signal: AbortSignal.timeout(180_000),
  body: JSON.stringify({
  "api": "@nlm-clinical-tables",
  "visibility": "public",
  "operation": "explain_diagnosis_code",
  "version": 1,
  "input": {
    "code": "E119"
  },
  "response": {
    "format": "json"
  }
}),
});
type ApiResult = { success: boolean; data?: { output: unknown }; error?: { message: string } };
const result: ApiResult = await response.json();
if (!response.ok || result.success === false) {
  throw new Error(result.error?.message ?? `HTTP ${response.status}`);
}
if (!result.data) throw new Error("Missing API response data");
console.log(result.data.output);
```

## Use from an AI assistant

Connect this tool to Claude Code, Claude Desktop, Cursor, VS Code, Codex and any MCP client as its own MCP server. Each method is a typed tool whose arguments are the method’s input.

- Server URL: `https://api.fous.com/mcp/tools/nlm-clinical-tables`
- Authorization: `Authorization: Bearer <Fous API key>`

**Tools**

- `explain_diagnosis_code`: Explain diagnosis code. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.
- `search_diagnosis_codes`: Search diagnosis codes. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.
- `fous_get_run`: the result of a run that was still going, by its `request_id`. Free.

Claude Code:

```bash
claude mcp add --scope user --transport http fous-nlm-clinical-tables https://api.fous.com/mcp/tools/nlm-clinical-tables --header "Authorization: Bearer ${FOUS_API_KEY:?Set FOUS_API_KEY to your Fous API key}"
```

To give the assistant every tool, connect `https://api.fous.com/mcp`: it finds one with `fous_search_tools` and runs it with `fous_run_tool`. Setup for other clients: https://fous.com/llms-full.txt.

## Use cases

- Find diagnosis codes from condition descriptions
- Look up official names for diagnosis codes
- Check a code’s category and chapter
- Determine whether a diagnosis code is billable

## FAQ

### Can I run it with my own inputs?

Yes. Change the inputs in Studio and press Run, or send new inputs from your code, or ask a connected AI assistant.

### Can I call this NLM Clinical Tables tool as an API?

Yes. Send a POST request to /v1/query with your Fous API key and the inputs, and get JSON back.

### How much does it cost?

Each completed run costs 1 credit. Failed runs without a completed receipt are free; completed work can remain charged if delivery is interrupted. With pay as you go, a credit costs 1¢. Monthly plans cost less per credit.

### Do I need a NLM Clinical Tables account?

No. You only need a Fous account.

### How current is the data?

Fous gets the data from clinicaltables.nlm.nih.gov when you run it. Some results are reused for up to 24 hours, and results that use your account or key are never reused. It was last verified on Oct 7, 2026.

### Which ICD-10-CM codes match a condition description?

Search diagnosis codes finds matching codes and official names from a plain-language condition description.

### What is the official name for an ICD-10-CM code?

Explain diagnosis code returns the official diagnosis name for a supplied code.

### Is an ICD-10-CM code billable?

Explain diagnosis code returns whether the code is sufficiently specific to bill.

## Related

- [Mayo Clinic API](https://fous.com/tools/mayo-clinic.md): Mayo Clinic provides health information from public condition pages, including condition overviews and, where available, diagnosis, treatment, home care, alternative medicine, and appointment preparation.
- [MedlinePlus API](https://fous.com/tools/medlineplus.md): MedlinePlus provides health information from the U.S. National Library of Medicine, including condition and symptom overviews and explanations of tests with matching pages.
- [ClinicalTrials.gov API](https://fous.com/tools/clinicaltrials-gov.md): ClinicalTrials.gov helps users find studies and view public trial records, including sponsor-run or funded studies; site distances are approximate, and contacts, eligibility, or exact dates may be missing.
- [WebMD API](https://fous.com/tools/webmd.md): Plain-language health condition and symptom guides from WebMD.
- [PubMed API](https://fous.com/tools/pubmed.md): PubMed searches medical and life-science articles by topic and retrieves one article’s abstract and publication details; abstracts and free full-text links may be unavailable.
- [NHS API](https://fous.com/tools/nhs.md): NHS provides condition and medicine guidance, with condition dates reflecting the latest pages used, and nearby England service listings ordered by distance; availability details may be missing.
- [NPI Registry API](https://fous.com/tools/npi-registry.md): NPI Registry returns public US provider search results with contact and taxonomy details, plus individual 10-digit NPI records with registry dates; fields may be missing.
- [Drugs.com API](https://fous.com/tools/drugs-com.md): Drugs.com provides public medicine guides, interaction and food or lifestyle warnings for 2–10 medicines, pill matches by imprint, color, or shape, and listed US cash prices by strength, form, and quantity.
- [All Health tools](https://fous.com/tools/category/health)