Under the federal HIPAA law, 45 C.F.R. 164.501, a designated record set is a group of records maintained by, or for, a covered entity that is used, in whole or in part, by, or for, the covered entity to make decisions about individuals and includes any item, collection, or grouping of information that includes PHI and is maintained, collected, used, or disseminated by, or for, a covered entity.
Therefore, if the person requesting the medical record requests the entire chart, or a portion of the chart, which includes records from another provider, if you have relied upon those records for treatment decisions, those records should be released along with your own medical records.
There is an exception to this general rule. That exception falls under a federal law protecting the records of a patient for drug or alcohol abuse. 42 C.F.R. Part 2.
Should you determine that the release of the records is inappropriate, you should state there are records you are not at liberty to release. You do not need to disclose the other provider, the origin of the records, the type of treatment involved, or the reason for the non-disclosure.