LOL, Of course this is if you have NO kids in the house. . I have a hard enough time hiding my shiat. . .
Yes, I know the feeling. My wife would NOT be happy if she knew. Here's what I do:
I have a few bottles of protein drinks in the bottom drawer of the fridge. She would never touch those. At the back of the bin, I keep an empty one, and I place the loaded and capped syringe inside.
(Sneaky, I know, but it works)