# Integrated natural language processing (NLP) for HealthLake
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AWS HealthLake provides integrated natural language processing (NLP) libraries for parsing, identifying, and mapping unstructured data stored in FHIR [`DocumentReference`](https://hl7.org/fhir/R4/documentreference.html) resource types.

**Important**  
Integrated NLP for HealthLake is turned off by default. To have it turned on, submit a support case using [AWS Support Center Console](https://console.aws.amazon.com/support/home#/). To create your case, log in to your AWS account and choose **Create case**.

HealthLake integrated NLP works by calling the Amazon Comprehend Medical `DetectEntities-V2`, `InferICD10-CM`, and `InferRxNorm` API actions. The actions append their results as an extension to the `DocumentReference` resource. When the Amazon Comprehend Medical API actions detect traits that are `SIGN`, `SYMPTOM`, and/or `DIAGNOSIS`, they generate a FHIR [`Linkage`](https://hl7.org/fhir/R4/linkage.html) resource. New `Condition` and `Observation` resources are created from entities identified with the traits of `SIGN`, `SYMPTOM`, or `DIAGNOSIS` and they are linked to the source document using the `Linkage` resource.

**Note**  
Although `GET` requests are supported for FHIR resources generated by HealthLake integrated NLP, FHIR API `search` functionality is not. To learn more about searching NLP extensions using HealthLake's integration with Athena, see [SQL index and query](integrating-athena.md).

**Contents**
+ [HealthLake Integrated NLP libraries](med-example.md)
+ [Using FHIR REST API interactions](nlp-rest-api.md)
+ [Search parameters for HealthLake integrated NLP](search-parameters-med.md)
+ [HealthLake integrated NLP example requests](cm-api-results.md)