I started taking 10 mg Lexapro daily in May this year to treat anxiety. Initially I felt better, so much so that at our first month consultation my physician recommended that I continue for one year.
Then, last month I started having more or less continuous headaches and lightheadedness. Reviewing Lexapro’s side effects, I found out that it can lower sodium levels in the blood, because of its effects on kidneys, and low sodium in the blood can cause headaches and lightheadedness.
I went back to the results of blood analyses done yearly for my annual check ups, and found out that my sodium levels had been pretty consistently at 139 mmoles/L.
In a blood analysis done in June of this year, one month after starting with Lexapro, my blood sodium level was 135 mmoles/L, just outside the normal range, which is 136-144 mmoles/L.
My physician didn’t think that it was low enough to cause my symptoms, but agreed to have my blood tested. The results showed that my blood sodium levels had already gone down to 131 mmoles/L. He immediately told me to wean off Lexapro, which I’ve successfully done over the course of three weeks.
My headaches and lightheadedness disappeared as I stopped taking Lexapro, so I think that it's possible that what you're experiencing is due to Lexapro.