Welcome to icliniq.com.
Based on your query, my opinion is as follows:
Hemoglobin level of 17.1 is near normal. Increased hemoglobin can be seen in conditions, where oxygenation is less, like hilly areas, lung disorders and the air you breathe is low in oxygen. To compensate red blood cells increases and hence the hemoglobin. In these conditions, hemoglobin can be more than 18 g% and we call this condition as polycythemia. At present, for you it is not polycythemia. Unless it is more than 18 g%, there is nothing to worry. No need to return it to normal. Few books do say that the range between 13.5 and 17.5 is normal in male. At present, there is nothing to worry. Blood donation is good and do continue it.
For further information consult a hematologist online -->https://www.icliniq.com/ask-a-doctor-online/hematologist