Dear Jill Albertson,
Thank you for posting your question on History Hub.
Army Personnel discharged before 12/21/2013 would need to contact the Veteran's Administration as they are the custodians of medical records. You can contact them here:
Records Management Center (VARMC)
4300 Goodfellow Blvd., Bldg# 104
St. Louis, MO 63120
Medical records for those discharged after 12/31/2013, can be found here:
AMEDD Record Processing Center
3370 Nacogdoches Road, Suite 116
San Antonio, TX 78217
I'm also including a link to the Standard From 180 (SF-180) which is used for requesting personnel and medical records. It has the custodial information and locations of the records you're seeking on page 3. It can be found here: https://www.archives.gov/veterans/military-service-records/standard-form-180.html
We hope this is helpful. Best of luck with your research!