TRT Dosage Calculator.

Testosterone for injection is sold by concentration — milligrams of hormone per millilitre of oil, most commonly 100 or 200 mg/mL for cypionate and enanthate. Your prescription, though, is written in milligrams per week. This calculator bridges the two. First it divides your weekly dose by how many times you inject to get the milligrams per injection. Then it divides that by the vial concentration to get the volume in millilitres. Finally it converts millilitres to units on a U-100 insulin syringe, where 100 units equals exactly 1 mL.

A worked example: 140 mg per week, split into two injections, from a 200 mg/mL vial. That is 70 mg per injection, ÷ 200 mg/mL = 0.35 mL, which reads as 35 units on a U-100 syringe. The weekly total is 0.7 mL.

The same weekly dose feels very different depending on how you split it. Long-ester testosterone (cypionate, enanthate) has a half-life of roughly 4–8 days, so a single large weekly shot produces a peak-and-trough curve — higher highs, lower lows, and often more mood and libido swing. Splitting the same weekly milligrams into two (every 3.5 days, "E3.5D") or into every-other-day injections flattens those swings and can reduce the rise in estradiol and hematocrit that drives many TRT side effects.

More frequent injections mean smaller volumes each time — which is why men on daily or EOD protocols use small U-100 insulin syringes rather than a larger intramuscular syringe. This calculator flags when your per-injection volume is too large for a 1 mL syringe or too small to measure accurately.

Dose, ester, injection site, and schedule are individual medical decisions made with a prescriber who monitors your total and free testosterone, estradiol, hematocrit, and PSA. Testosterone raises red-blood-cell count and can suppress fertility; unmonitored use carries real cardiovascular and prostate considerations. Concentrations and pharmacy compounding also vary — always confirm the number printed on your own vial.

Use this tool to check your arithmetic and understand what your prescribed dose translates to on the syringe — never to self-prescribe, adjust your dose without your clinician, or source testosterone outside a pharmacy.