I m 42 year old, I have hemoglobin 16.9, family doctor suggest this is high, how can I reduce?

First, why? You need to know why the hemoglobin is elevated. There are many causes, including lung disease (smoking/emphysema), medications, occasionally sleep apnea, and bone marrow disorders. Living at high altitude can also be a cause. Before trying to reduce the hemoglobin, you first need to know why it is elevated. See your doctor.