This from the TSA's site: I used Diabetes as the underlying reason for carrying unused syringes, but any prescribed injectable medication would allow them:
Diabetes
Notify the Security Officer that you have diabetes and are carrying your supplies with you. The following diabetes-related supplies and equipment are allowed through the checkpoint once they have been screened:
Insulin and insulin loaded dispensing products (vials or box of individual vials, jet injectors, biojectors, epipens, infusers, and preloaded syringes;
Unlimited number of unused syringes when accompanied by insulin or other injectable medication;
lancets, blood glucose meters, blood glucose meter test strips, alcohol swabs, meter-testing solutions;
Insulin pump and insulin pump supplies (cleaning agents, batteries, plastic tubing, infusion kit, catheter, and needle); Insulin pumps and supplies must be accompanied by insulin.
Glucagon emergency kit;
Urine ketone test strips;
Unlimited number of used syringes when transported in Sharps disposal container or other similar hard-surface container.
Sharps disposal containers or similar hard-surface disposal container for storing used syringes and test strips.
Jim