Cause for concern?

The past couple weeks I've been giving my BP shots for an RI. every single time she fights against it and is generally showing me that the shot hurts. Well today I gave her the shot and she didn't even flinch. She showed no emotion when the needle went in and none when I injected her, which the vet said would sting a bit. Any idea why she appeared immune tonight?

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I've been giving my BP shots for an RI as well.. it seems that some days she'd fight it more than others. I don't think I'd worry about it too much if her all around behaviour hasn't changed. Maybe if she is acting strange in her enclosure and when you handle her as well, get it looked into? That's just my thoughts... I'd imagine some spots would be more painful than others and also would depend on how tense she is. I'm following this thread to see what more experienced people say, though. :)