From the TSA website:
Medically required liquids, such as baby formula and food, breast milk and medications are allowed in excess of 3.4 ounces in reasonable quantities for the flight. It is not necessary to place medically required liquids in a zip-top bag. However, you must tell the Transportation Security Officer that you have medically necessary liquids at the beginning of the screening checkpoint process. We recommend, but do not require, that medication be labeled to facilitate the security process.
Liquids, gels, and aerosols are screened by X-ray and medically necessary items in excess of 3.4 ounces will receive additional screening. A passenger could be asked to open the liquid or gel for additional screening. TSA will not touch the liquid or gel during this process. If the passenger does not want a liquid, gel, or aerosol X-rayed or opened for additional screening, he or she should inform the officer before screening begins. Additional screening of the passenger and his or her property may be required, which may include a patdown.
Accessories required to keep medically necessary liquids, gels, and aerosols cool – such as freezer packs or frozen gel packs – are permitted through the screening checkpoint and may be subject to additional screening. These accessories are treated as liquids unless they are frozen solid at the checkpoint. If these accessories are partially frozen or slushy, they are subject to the same screening as other liquids and gels.
Supplies that are associated with medically necessary liquids and gels – such as IV bags, pumps and syringes – are allowed through a checkpoint once they have been screened by X-ray or inspection. The passenger should declare these items to an officer and separate them from other belongings for screening.