Try different pharmacies, it may be a policy of that pharmacy.
Also dress nicely and mainstream, try to look older/more mature if you are relatively young, be really polite, know what you're talking about (ask for the syringes by name and size), act confident and like you belong there (<-most important one), don't offer an explanation unless they ask, etc. And as others mentioned, sometimes buying a larger quantity can help.
If they asked to see a prescription I would usually just say I'm visiting from out of town and don't have it with me, or that I am purchasing them for my father who is diabetic, or both - I'm purchasing for my father and we are from out of town. If they said they wanted to see the bottle, I'd say I don't have it on me as I didn't even think that would be required, I buy from this chain all the time back home and have never once been asked for that before, I really don't have time to go all the way back to my auntie's house where we are staying, my father sent me because he was short on time and I'll be sure to remember to bring it next time. But it usually never got to that point. Or if there are a bunch of pharmacies in the area I'd just move on to the next one.
You can read up on insulin-dependent Type 1 diabetes in case they ask you any questions to test you. I have not found the "vitamin injections" excuse to work in my experience. A person would use a different type/size of syringe for vitamins and if you say it's for your pet they say why didn't the vet give you some.
Sometimes I tried to distract them by, for example, purchasing another item (that would not be associated with a drug user), like if I walked up with a pack of gum or some make-up or something, and said "I'd like you to ring this up for me please and I would also like a package of BD 1CC insulin syringes in longs please," or flattered the cashier like, "I love your earrings, where did you get them?" but also not going over the top or chattering
excessively.
Also see if there is a needle exchange in your area - although I don't
think there are any in Mississippi

It makes me so sad the lengths people have to go to to get harm reduction supplies. It is so ridiculous, as if they think that everyone is going to quit using drugs because it's hard for them to get clean needles
