TRT Dosage Calculator - assumptions and limitations

Assumptions

• Per-injection mg = weekly target / doses per week

  The mg-per-injection split is dimensional - what you put in the syringe is what reaches the IM tissue. The calculator does not apply pharmacokinetic, half-life, or ester-specific adjustments to the per-injection mass itself; ester-driven peak/trough behaviour is surfaced separately on the 'Estimated drug levels' chart and the ester-cadence cadence-hint warning.

• Ester selector with cadence hint

  Cypionate, enanthate, and other ester labels do not alter the per-injection mg/mL math (which is purely arithmetic), but the calculator does surface a soft info note when the chosen cadence is longer than the ester's typical half-life supports. Half-lives: cypionate ~8 d (Behre 1990; Depo-Testosterone USPI), enanthate ~4.5 d (Snyder 1980), propionate ~0.8 d (Nieschlag 1976), undecanoate ~21 d (Aveed USPI), mixed esters ~4 d (Sustanon SmPC). The cadence hint is informational only.

• Schedule math assumes consistent intervals

  doses_per_week = 7 / interval_days assumes the chosen cadence is followed exactly across the week. Real adherence has missed/late doses, and ester-specific peak/trough swing is surfaced separately on the 'Estimated drug levels' chart rather than baked into the per-injection mg/mL output.

• U-100 syringe units (definitional)

  U-100 insulin syringes are defined by USP <1601> and ISO 8537:2016 as 100 units = 1 mL (so 1 unit = 0.01 mL). The conversion units_per_injection = mL_per_injection * 100 is dimensional, not modelled. Confirm against your specific syringe markings.

• Vial usage rounds down (conservative policy)

  Doses per vial floors to whole doses; days of supply counts full doses only. Floor is the tightest bound that does not overstate supply - the partial-dose remainder is surfaced separately as 'Leftover' so nothing is hidden. This is a documented rounding policy, not a model.

Formulas used

Each output is derived from one of the formulas below. They run client-side, so what you see in the calculator is what the math actually does.

1. 1. Doses per week

   doses_per_week = 7 / interval_days

2. 2. Mg per injection

   mg_per_injection = weekly_mg / doses_per_week

3. 3. mL per injection

   mL_per_injection = mg_per_injection / concentration_mg_per_mL

4. 4. Weekly mL

   weekly_mL = weekly_mg / concentration_mg_per_mL

5. 5. U-100 syringe units (estimate)

   units_per_injection = mL_per_injection * 100

6. 6. Vial volume (mL)

   vial_volume_mL = vialSize (when unit = mL) OR vialSize / concentration_mg_per_mL (when unit = mg)

7. 7. Doses per vial

   doses_per_vial = floor(vial_volume_mL / mL_per_injection)

8. 8. Days of supply

   days_of_supply = doses_per_vial * interval_days

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