UMLS Python API Docs | dltHub

UMLS Terminology Services (UTS) provides a REST API for accessing medical terminology data and concept information. The REST API base URL is https://uts-ws.nlm.nih.gov/rest and Requests require a UMLS API key, which can be passed as a query parameter or via an Authorization header..

dlt is an open-source Python library that handles authentication, pagination, and schema evolution automatically. dlthub provides AI context files that enable code assistants to generate production-ready pipelines. Install with uv add "dlt[hub]" and start loading UMLS data in under 10 minutes.

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What data can I load from UMLS?

Here are some of the endpoints you can load from UMLS:

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How do I authenticate with the UMLS API?

Authentication is performed by passing a UMLS API key. It can be provided as a query parameter named 'apiKey' in the URL or within the 'Authorization' header using the format 'Bearer <API_KEY>'.

1. Get your credentials

To obtain your UMLS API key: 1. Sign in to your account on the UMLS Terminology Services (UTS) website (https://uts.nlm.nih.gov/uts/profile). 2. Navigate to your 'My Profile' area. 3. Click 'Edit Profile'. 4. Select the 'Generate new API Key' checkbox. 5. Click 'Save Profile' to generate and view your API key.

2. Add them to .dlt/secrets.toml

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[sources.umls_source]
api_key = "your_api_key_here"

dlt reads this automatically at runtime — never hardcode tokens in your pipeline script. For production environments, see setting up credentials with dlt for environment variable and vault-based options.

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How do I set up and run the pipeline?

Set up a virtual environment and install dlt:

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uv init
uv add "dlt[hub]"

1. Install the dlt AI harness:

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uv run dlthub ai init --agent <your-agent> # <agent>: claude | cursor | codex

This installs project rules, a secrets management skill, appropriate ignore files, and configures the dlt MCP server for your agent. Learn more →

2. Install the rest-api-pipeline toolkit:

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uv run dlthub ai toolkit install rest-api-pipeline

This loads the skills and context about dlt the agent uses to build the pipeline iteratively, efficiently, and safely. The agent uses MCP tools to inspect credentials — it never needs to read your secrets.toml directly. Learn more →

3. Start LLM-assisted coding:

Use /find-source to load data from the UMLS API into DuckDB.

The rest-api-pipeline toolkit takes over from here — it reads relevant API documentation, presents you with options for which endpoints to load, and follows a structured workflow to scaffold, debug, and validate the pipeline step by step.

4. Run the pipeline:

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uv run python umls_pipeline.py

If everything is configured correctly, you'll see output like this:

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Pipeline umls_pipeline load step completed in 0.26 seconds
1 load package(s) were loaded to destination duckdb and into dataset umls_data
The duckdb destination used duckdb:/umls.duckdb location to store data
Load package 1749667187.541553 is LOADED and contains no failed jobs

Inspect your pipeline and data:

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uv run dlthub show

This opens the Pipeline Dashboard where you can verify pipeline state, load metrics, schema (tables, columns, types), and query the loaded data directly.

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Python pipeline example

This example loads /search and /content from the UMLS API into DuckDB. It mirrors the endpoint and data selector configuration from the table above:

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import dlt
from dlt.sources.rest_api import RESTAPIConfig, rest_api_resources

@dlt.source
def umls_source(apikey=dlt.secrets.value):
    config: RESTAPIConfig = {
        "client": {
            "base_url": "https://uts-ws.nlm.nih.gov/rest",
            "auth": {"type": "api_key", "api_key": apikey, "name": "Authorization", "location": "query"},
        },
        "resources": [
            {"name": "concepts", "endpoint": {"path": "content/{version}/CUI/{CUI}", "data_selector": "result"}},
            {"name": "relations", "endpoint": {"path": "content/{version}/CUI/{CUI}/relations", "data_selector": "result"}}
        ],
    }
    yield from rest_api_resources(config)


def get_data() -> None:
    pipeline = dlt.pipeline(
        pipeline_name="umls_pipeline",
        destination="duckdb",
        dataset_name="umls_data",
    )
    load_info = pipeline.run(umls_source())
    print(load_info)

To add more endpoints, append entries from the resource table to the "resources" list using the same name, path, and data_selector pattern.

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How do I query the loaded data?

Once the pipeline runs, dlt creates one table per resource. You can query with Python or SQL.

Python (pandas DataFrame):

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import dlt

data = dlt.pipeline("umls_pipeline").dataset()
sessions_df = data.concepts.df()
print(sessions_df.head())

SQL (DuckDB example):

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SELECT * FROM umls_data.concepts LIMIT 10;

In a marimo or Jupyter notebook:

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import dlt

data = dlt.pipeline("umls_pipeline").dataset()
data.concepts.df().head()

See how to explore your data in marimo Notebooks and how to query your data in Python with dataset.

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What destinations can I load UMLS data to?

dlt supports loading into any of these destinations — only the destination parameter changes:

Change the destination in dlt.pipeline(destination="snowflake") and add credentials in .dlt/secrets.toml. See the full destinations list.

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Next steps

Continue your data engineering journey with the other toolkits of the dltHub AI harness:

• data-exploration — Build custom notebooks, charts, and dashboards for deeper analysis with marimo notebooks.
• dlthub-platform — Deploy, schedule, and monitor your pipeline in production.

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uv run dlthub ai toolkit install data-exploration
uv run dlthub ai toolkit install dlthub-platform

• How to deploy a pipeline
• How to explore your data in marimo Notebooks
• How to query your data in Python with dataset
• Join the dlt community on Slack