I am on oxygen for asthma and altitude, but my levels are over 90 all day. i use it at night. can i ever stop? heart and lung tests were normal. is it harmful to use if not needed?

Depends: The answer depends on the testing you have had done and the pulmonary dr. Following your case. Some people have good pulse ox reading during the day, but when an overnight pulse ox test is performed they 'desaturate' to low levels that are troublesome, thus oxygen is rx'd for night time use. Check with the prescribing dr. On how your condition is doing, and keep going to follow-up appts.Good luck.

Good questions: If your oxygen saturation is >90%, you don't need to use the oxygen. There is no harm in using it other than the dryness it may cause in your nose. You may need it walking - many people are normal at rest but desaturate with exercise - have you been tested? Do you even need it at night?