More is not always more. In pharmacology, dose-response curves are not straight lines — they are curves, and most of them flatten out or turn downward eventually. With testosterone, the evidence is fairly clear: benefits accumulate as you move from deficient into the normal physiological range, and then they largely plateau. What keeps increasing above that ceiling is not benefit. It is risk.
The normal physiological range for total testosterone in adult men is approximately 300 to 1050 ng/dL. Supraphysiological means above that ceiling — levels the male body does not produce naturally under any circumstance. The relevant clinical question is not whether supraphysiological testosterone is problematic. The data settled that years ago. The question is how common it is in therapeutic TRT patients who are not actively trying to achieve it — and the answer relates directly to the delivery format we discussed in the previous post.
How You Get There Without Trying
A patient prescribed 100 mg of testosterone cypionate weekly and injecting intramuscularly can reach peak serum levels well above 1050 ng/dL in the first 24 to 48 hours after injection — even though their average level across the week might fall within the normal range. The lab work taken at trough looks fine. What happens at the top of the cycle is a different story.
This is an important nuance: supraphysiological exposure is often not the result of an excessive prescription. It is the result of an infrequent delivery format that produces a large initial spike. The total dose is therapeutic. The peak is not.
The Blood-Thickening Problem
Testosterone stimulates erythropoiesis — red blood cell production — primarily through increased erythropoietin secretion from the kidneys. At physiological testosterone levels, this is a normal and beneficial process. At supraphysiological peaks, the work orders pile up. Red blood cell count rises beyond the therapeutic benefit range, and blood viscosity increases. Clinically, erythrocytosis is flagged when hematocrit exceeds 54% — at which point blood has thickened enough that clot formation becomes more likely and the risk of stroke and cardiovascular events rises.
What the Cardiovascular Data Actually Shows
Multiple large analyses have examined cardiovascular outcomes by testosterone delivery method. Initiating testosterone therapy with intramuscular injections was associated with higher hazard of cardiovascular events, hospitalizations, and all-cause mortality compared to initiating with transdermal gels. The TRAVERSE trial — the definitive cardiovascular safety study of testosterone therapy — used daily transdermal gel and found no increase in major cardiovascular events.
The Estrogen Problem at the Top of the Spike
The problem with injection peaks is that a sharp testosterone rise drives a proportionally larger aromatization response. The estradiol spike that follows an injection peak does not resolve on the same schedule as the testosterone. In some patients, estradiol remains elevated even as testosterone descends toward trough — creating an out-of-phase hormonal environment that stable transdermal delivery largely avoids.
The Dose-Response Curve Doesn’t Keep Going Up
The benefits of testosterone therapy follow a saturation pattern. Substantial gains appear as levels move from deficient into the low-to-mid normal range. Above the mid-normal range, incremental benefit from additional testosterone becomes small. Risk, unfortunately, does not flatten at the same point. For therapeutic TRT, the goal is not the highest achievable serum level. It is the most stable level within the therapeutic range.
