M25, xray,ecg,cbc all normal. but oxygen saturation using a fingertip oximeter drops below 90 and sometimes 80 while sitting down or laying down. is this normal or do i have a disease the doctors missed?

!.Are you a smoker? 2.What is your occupation? 3. Have you had blood work done in terms of hemoglobin? 4.What is your family history.? There is a condition called Methhemoglobinemia which could be inherited commonly acquired due to medications such as nitroglycerin or dapsone etc. Hence check with your physician for this. Your list of medication is important prescription as well as over the counte