From the HHS Office for Civil Rights website:
Get it.
Ask your doctor. You have the right to see and get copies of your health information - PDF. In most cases, you can get a copy the way you want it, such as by e-mail. While your doctor normally has up to 30 days to provide you a copy of your information, your doctor often can provide the information much sooner than that. If your doctor offers a web portal, you may be able to easily view and download your health information whenever you want. There are a few exceptions to getting your information, but you can’t be denied access for not paying your medical bill. Your doctor can, however, charge you a reasonable fee 
for a copy of your health information. The fee may not be a per page fee if your information is stored electronically.
Check it.
Check to make sure your health information is correct and complete. If you think something is wrong or missing, you can ask your doctor to fix it. Your doctor might not agree, but you always have the right to have your disagreement added to your record.
Use it.
Having access to your health information means better communication between you and your doctors, less paperwork and greater control over your health. You can request that your doctor share your information directly with others , like family members, a caregiver, a mobile application or “app,” or a researcher.