In order to carry insulin and syringes on board, you are required to bring a doctor's note and a prescription (Korean or English).
Also, you can carry only as much as you can use on the plane, and have to check-in a bag with extra insulin and syringes.
For pills, possible to carry-on and check in.
If you carry them on the plane, you can take as much as you have to use on the plane.
There may be additional verification procedures if it is suspected as drug.
Also, for liquid medicine (including ointments), they must be processed in accordance with the carry-on regulations for liquid and gell type.
However, if you bring medical supplies to an overseas country, you can get a ban from customs and security checkpoints. Please bring proof documents such as English doctor's report.
