The Unified Medical Language System UMLS consolidates and standardizes health and biomedical vocabularies from several important resources to enable interoperability between computer systems. Now you can use MyGene.info service to obtain UMLS Concept Unique Identifiers (CUIs).

Here are a few quick examples:

{
      "_id": "1017",
      "_score": 149.0478,
      "name": "cyclin dependent kinase 2",
      "symbol": "CDK2",
      "umls": {
        "cui": "C1332733"
      }
}

What are you waiting for? Try it out yourself.