If you are traveling within the U.S., you’ll be fine. TSA workers don’t know or care if B12 is water or oil-based. TSA doesn’t screen for drugs. It pretty much says so on its website. You could travel with a vial with a UGL label on it and nothing would happen. There are various articles out there about traveling with drugs. I remember one person had pot in a carry on and was pulled aside for extra screening. TSA went through the bag and took things out, including the pot, then put everything back and sent the person on his way. Once at the Ft. Lauderdale airport, I had test in my carry on and was pulled aside. They went through my bag, looked at the test closely because it was a liquid, then put everything back and off I went. I wasn’t pulled aside because of the test. It was just a random extra screening. That said, some prudence is a good idea. Using B12 labels and a diabetic traveling kit, and putting gear in your checked luggage, is a good idea. After my experience in Ft. Lauderdale, I put injectables in my checked luggage, sans B12 labels, and nothing has ever happened, and several times there has been a card in my checked luggage saying TSA screeners had gone through it. This happened a couple of times when I also had cannabis tablets in a pill jar.
If you are a coke dealer and your bag is stufffed full of it, then TSA would call the authorities, but outside of situations like that, you don’t need to worry.