I started on 10 mgs of Lexapro and experienced tolerable but not fun side effects for about a month. After then, I started feeling a lot better. About a year later, my doctor and I decided to try 20 mgs. Again, I experienced tolerable but not fun side effects for about a month (maybe two at most) and then started feeling better. Again, after a year of being on 20 mgs, my doctor and I increased my medication to 30 mgs. This time I only experienced side effects for a couple weeks (one month max) and started feeling better. So, for me, the side effects lasted about a month with each increase in dosage. Hope this helpts, but it could really be different for anyone. If your side effects aren't tolerable for the time being, tell your doctor.