Anyone experience lethargy or lack of energy while taking Losartan for blood pressure?

Of course. Losartan is infamous for causing lethargy. It sounds like you have white coat hypertension. I do not and take 100 mg Losartan. I sleep very well usually but Losartan can also cause insomnia. I do feel like a zombie and know I do not recall things as well. I have hit my head numerous times due to not being fully awake. Tell your Dr your concerns. Coffee is not advisable because it raises pressure so you can’t use that up wake up either. It’s pretty tough. Sometimes I worry I will lose my job.