Transdermal Testosterone: Why Concentration Is Not the Same as Absorption

Transdermal testosterone calculations can look straightforward: divide the amount in a container by the number of applications, then multiply by an estimated absorption percentage.

The problem is that accurate arithmetic cannot compensate for unverified assumptions. The amount dispensed onto the skin and the amount reaching circulation are different measurements.

What Are You Actually Measuring?

Three quantities need to be distinguished:

MeasurementMeaningProduct concentrationAmount of active ingredient per unit of finished productApplied amountAmount of active ingredient placed on the skinSystemic exposureDrug reaching circulation over time

Knowing the first two does not automatically establish the third. A concentration calculation also cannot prove that a homemade preparation is evenly mixed, stable or accurately dispensed.

Why a “Squirt” Is Not a Reliable Unit

A pump actuation is meaningful only when the dispenser’s output and the finished formulation have been characterised.

Dividing the total powder added by an assumed number of pump presses gives a theoretical average. It does not establish that every press contains that amount, or that all the powder remains uniformly distributed throughout use.

The original article’s claims about the carrier’s powder capacity and number of applications are therefore insufficient to establish reliable dosing.

Why the Assumed Absorption Percentage Matters

The original calculation assumes 35% absorption. Without appropriate testing of that exact formulation, this is an assumption rather than a measured result.

Even licensed testosterone gels have product-specific instructions. The testosterone gel 1.62% prescribing information explicitly states that its application sites and doses are not interchangeable with other topical testosterone products. It also describes dose adjustment using blood testosterone measurements.

A guessed absorption percentage cannot reliably establish an equivalent injectable dose.

Can One Formula Apply to Every Steroid Powder?

No universal recipe is established by the supplied information. Testosterone, nandrolone, trenbolone and other compounds cannot be assumed to have identical solubility, stability or skin penetration.

The distinction between a parent hormone and an ester also matters. Substituting one ingredient for another requires formulation-specific evidence, rather than simply repeating the same calculation.

Does Mixing or Warming Validate the Product?

Shaking, warming or observing that a powder appears to dissolve does not establish the finished product’s potency, uniformity or stability.

The FDA’s explanation of compounded-drug risks notes that compounded medicines do not undergo FDA premarket review for safety, effectiveness and quality. Professional compounding can meet particular medical needs, but a home mixture does not provide the same preparation controls or clinical oversight.

Skin Transfer Is Another Important Consideration

Topical testosterone can unintentionally expose other people through contact with treated skin.

The AndroGel prescribing information includes precautions against secondary exposure, particularly involving women and children. Users of prescribed products should follow their specific instructions for handwashing, covering application sites and avoiding transfer.

What Makes a Dose Clinically Meaningful?

Reliable transdermal treatment requires more than dividing milligrams by pump presses. It depends on a characterised formulation, a suitable dispenser, product-specific instructions and assessment of the patient’s response.

For prescribed testosterone, a pharmacist or clinician can explain what the labelled amount represents and how monitoring guides treatment. Homemade concentration calculations should not be presented as proof of absorption, effectiveness or safety.