It’s a rare side effect, needless to say more frequent in mice. It’s always difficult to disentangle the effect of antidepressants in improving appetite, as opposed to a direct side effect in diabetic control. Biochemically, it’s difficult to postulate a direct effect on BG control because of the way Venlafaxine works. The effect is equally occasionally reported in the use of Amitryptiline, an older antidepressant which works in an entirely different way, but is equally inexplicable biochemically. So who knows? In any event, the caution only seems to apply when starting treatment.
I would have thought if you’ve been on Venlafaxine for 6 months and you have only recently had high BGs then the chances of Venlafaxine being the cause are close to zero, or non existent.
What I do know is that under NO circumstances should you stop Venlafaxine suddenly. It must be tailed off gradually, otherwise some very unpleasant symptoms can occur.