The best thing to do is to discuss this question with your primary care physician
. The answer to this question depends how high your blood counts were prior to you starting the testosterone shots. A hemoglobin of 16.8 is above average, but for a man is not all that higher than normal. Certainly no physician would recommend you donate blood for the purposes of reducing that hemoglobin. I would say that if you baseline hemoglobin is lower say 15 mg/dl, then perhaps it will take about 1.5 to 3 months for your levels to drop. This is simply based on how long a red blood cell typically lives which is roughly 3 months. After most of your red blood cells have turned over, your hemoglobin will be whatever it is without the testosterone.
I suggest that for further evaluation of this issue, you should schedule an appointment with your primary care physician. Your doctor
may choose to recheck your blood counts a few months after stopping the testosterone. Your doctor might also choose not to check, which is probably just as appropriate. If your doctor is worried that you have some other blood condition that has increased your hemoglobin, then further testing might be needed. A condition known as polycythemia vera (PCV) is probably the most well known cause of elevated red blood cells.