Why would my right side of lung upon auscultation sound diminished. my dr. said i have asthma. could this be?

Lung sounds can be: diminished for several reasons. Sometimes there is fluid or a pneumonia; sometimes there is a partial collapse of the lungs (which could happen in asthma). I would ask your doctor for more of an explanation and you may need a chest X-ray.

Yes...: There are a variety of diagnoses that cause diminished breath sounds on exam, which signify poor air movement in the airways. This can occur with asthma or COPD (where bronchospasm or other mechanisms limit airflow), pleural effusion, pneumothorax, or pneumonia (among others). In any of these cases, it is important to follow up with your doctor to be sure you are treated appropriately.