Sodiun 137 and Potassium 3.80. Should I be concerned? Does it mean I'm dehydrated?

Low K. Your sodium is normal and you have low normal K. Lans never tell the true picture. If you have ongoing losses like nausea diarrhea along with dry mouth dizziness etc in varying degree they mean loss of body fluid and labs may be ok. So for now your numbers are ok and call your MD of you have symptoms. Best of luck .