Hemoglobin

HGB is the standard abbreviation for hemoglobin, the iron-containing protein inside red blood cells that carries oxygen from your lungs to the rest of your body. On a complete blood count (CBC) it's reported in g/dL and sits right next to hematocrit (HCT), which measures the same thing a different way. The two nearly always move together.

The adult male reference range is roughly 13.5–17.5 g/dL (women run lower, about 12–15.5 g/dL). Exact cutoffs vary slightly by lab and altitude. On TRT, men frequently sit at or above the top of this range.

Testosterone stimulates erythropoietin and suppresses hepcidin, which together push your bone marrow to make more red blood cells — so hemoglobin and hematocrit both climb. This is the single most common measurable side effect of TRT. It's usually manageable by adjusting your dose or injection frequency, and it's why clinicians trend HGB and HCT together at every draw.

17.1 g/dL sits right at the top of the male reference range — not abnormal, but worth watching. On TRT it's common. The number to watch alongside it is hematocrit; if HCT is creeping toward 52–54%, that's usually the trigger for a protocol change rather than the hemoglobin figure alone.

15 g/dL is comfortably mid-range and unremarkable for a man. 17.4 g/dL is at the upper edge of normal — fine as a one-off, but on TRT it's worth trending alongside hematocrit to make sure the trajectory isn't heading past HCT 54%. A single value matters less than the trend.

A hemoglobin of 20–22 g/dL is clearly elevated and, on TRT, points to significant erythrocytosis (polycythemia). Hemoglobin above 20 g/dL is also the point at which most blood-donation centers will defer you. This level usually warrants prompt attention: hydration check, a repeat draw, and a conversation with your physician about lowering or splitting your dose, and possibly therapeutic phlebotomy.

Almost certainly not — that value is in g/L, not g/dL. Many labs outside the US report hemoglobin in grams per liter, so 125 g/L is simply 12.5 g/dL, which is a normal-to-low-normal figure. To convert g/L to g/dL, divide by 10 (150 g/L = 15 g/dL).

Most TRT clinicians are comfortable with hemoglobin anywhere in the reference range and simply track it alongside hematocrit. If HGB climbs above ~18 g/dL, that usually corresponds to hematocrit approaching the 52–54% zone where intervention is considered — smaller, more frequent injections, a lower dose, better hydration at the draw, or blood donation. There's no single magic number; the trend and your hematocrit matter more.