Is insomnia caused by Effexor a side effect that will diminish, go away or persist?

. Hello Maryam, thank you for your question. Insomnia is a common side effect of taking Fexor. Generally, this side effect should start to improve within a month of taking the medication at the same dose. Taking the medication as early as possible in the morning may help reduce the stimulating effect in the evening and improve your insomnia. If the side effect does not improve within a month, it is best to speak with your doctor about getting a medication to help you sleep.