Splitting 100mg/Week TRT Into Every-Other-Day Microdoses

TRT microdose every other day from 100mg weekly: the core math

To run a TRT microdose every other day from 100mg weekly, you keep the prescribed weekly total fixed and split it across more frequent, smaller injections. "Every other day" (EOD) means dosing on a roughly 2-day interval, which works out to about 3.5 injections per week.

The split is one division:

• Weekly total ÷ injections per week = dose per injection
• 100 mg ÷ 3.5 = 28.57 mg per EOD injection (rounds to ~28-29 mg)

Splitting the same weekly milligram total into smaller, more frequent doses does not change the total amount delivered over a week; it only changes how it is spread out. For background on why a weekly figure is the anchor, see what mg per week means and what a split dose is.

Why EOD is ~3.5 injections, not 4

A week is 7 days. Dosing every 2 days gives 7 ÷ 2 = 3.5 doses per week on average. In practice the calendar alternates: across a 14-day fortnight you take 7 injections (days 1, 3, 5, 7, 9, 11, 13), which is exactly 7 doses in 14 days, or 3.5 per week.

For how these frequencies compare in practice, see daily vs twice-weekly vs every 3.5 days and the broader TRT protocols explained overview.

From milligrams to millilitres to syringe units

Your syringe is marked in units (a U-100 insulin syringe), not milligrams. Two conversions get you there:

1. mg → mL: dose (mg) ÷ concentration (mg/mL) = volume (mL)
2. mL → units: volume (mL) × 100 = units (on a U-100 syringe, 1 mL = 100 units, so 0.01 mL = 1 unit)

The concentration printed on your vial label matters more than anything else here. The two most common testosterone concentrations are 200 mg/mL and 100 mg/mL, and they give very different unit fills for the same 28.57 mg dose. See syringe units explained and how to read an insulin syringe if the unit markings are unfamiliar.

Worked example: 28.57mg EOD at 200mg/mL

Worked example: 28.57mg EOD at 100mg/mL

Per-injection units at a glance

This table holds the 100 mg/week total constant and shows the EOD (28.57 mg) microdose in units for the two common concentrations, alongside other split frequencies for comparison.

Because EOD fills at 200 mg/mL land near 14 units, a 0.3 mL syringe is the natural fit. At 100 mg/mL the ~29-unit fill still fits a 0.3 mL barrel. For choosing barrel size, see 0.3mL vs 0.5mL vs 1mL syringes.

Rounding, dead space, and accuracy notes

28.57 mg does not land on a whole unit at either concentration, so some rounding is unavoidable. A few practical points on the measurement side:

• Round to the nearest readable mark. At 200 mg/mL, 14.3 units rounds to 14 or 15 units — a difference of about 0.5 mg per shot, which is small relative to a 28.57 mg dose.
• Be consistent. Rounding the same way every injection keeps your weekly total close to the prescribed 100 mg.
• Dead space wastes drug. The hub and needle retain a small volume after injecting. With tiny EOD fills this matters proportionally more; low-dead-space insulin syringes minimise it.
• Never reuse a needle or syringe. Use a fresh sterile single-use syringe for each injection, per standard safe-injection practice.
• Confirm with the calculator. Enter your exact weekly total, EOD frequency, and vial concentration into the TRT Microdosing Calculator to get the unit fill for your specific numbers rather than relying on the rounded examples above.

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