What are TRT protocols? frequency, dose maths & per-shot units

The four common Testosterone (TRT) protocols

Every injectable protocol below starts from one number: the prescribed weekly dose in mg. The Endocrine Society guideline frames Testosterone (TRT) around restoring testosterone into the mid-normal range using the lowest effective dose, then monitoring on bloodwork rather than chasing a fixed schedule (Bhasin et al., 2018). What changes between protocols is only the frequency — how many pieces that weekly total is cut into.

Once-weekly

The whole weekly dose goes in one shot. Simplest to remember, but a long-ester depot like enanthate peaks a day or two after injection and drifts down over the week, producing the widest peak-to-trough swing (Schürmeyer & Nieschlag, 1984). Common in older protocols and self-administered enanthate.

Twice-weekly

The weekly dose is split into two equal shots roughly 3-4 days apart (for example Monday and Thursday). Each shot is half the volume of the once-weekly draw, and the trough is noticeably higher. This is the most common modern starting protocol.

Every 3.5 days (E3.5D)

A tighter version of twice-weekly that fixes the gap at exactly half a week, so the two shots are evenly spaced. The per-shot mg is identical to twice-weekly; the only change is calendar regularity. See daily vs twice-weekly vs every 3.5 days for the frequency trade-offs.

Daily microdosing

The weekly dose is divided by seven and injected subcutaneously each day. Blood levels are the steadiest of any protocol, but the daily draw can be tiny — sometimes only a handful of units — which is why readability and dead space start to matter.

Protocol comparison: weekly mg and per-shot units

The table below takes three representative weekly doses and shows the per-injection volume and U-100 units for each protocol, all on a 200 mg/mL vial — the standard testosterone cypionate concentration on the US label (DailyMed, 2021). Units are simply milliliters × 100.

Read down a column to see how the same weekly dose shrinks the per-shot draw as frequency rises. A 100 mg/week patient draws 50 units once a week, 25 units twice a week, or roughly 7 units daily — identical drug, very different syringe marks.

How this is calculated

Every figure above comes from two arithmetic steps, with no rounding tricks:

1. Per-shot mg = weekly mg ÷ shots per week.
2. Draw volume (mL) = per-shot mg ÷ vial strength (mg/mL).
3. U-100 units = draw volume × 100.

So a 140 mg/week dose on twice-weekly = 70 mg per shot; 70 ÷ 200 = 0.35 mL; × 100 = 35 units. The same 140 mg/week on daily = 20 mg per shot; 20 ÷ 200 = 0.10 mL = 10 units. The weekly mg never changed — only the divisor did. HCG and an AI never enter this maths: they are dosed in IU and mg respectively, drawn separately, and covered in their own calculators.

Worked examples

With or without HCG and an AI

Protocols are often described as "T-only", "T + HCG", or "T + HCG + AI". These add-ons change what you inject and how many injections you do — not the testosterone dose maths. HCG (to support testicular function) is dosed in international units and drawn from its own reconstituted vial. An aromatase inhibitor such as anastrozole controls estradiol and is usually an oral tablet, so it has no syringe volume at all. The testosterone column in the table above stays exactly the same whether or not these are present.

That separation matters for safety: blending unrelated drugs into one "total units" figure is how dosing errors happen. Keep each drug's maths independent, and follow CDC safe-injection practice — a new sterile needle and syringe for every injection (CDC, 2024).

Choosing and checking a protocol

Frequency is a clinical decision, not a maths output: your prescriber sets the weekly dose and how often to split it based on symptoms, bloodwork, ester, and how you tolerate peaks. Once that is fixed, the arithmetic is deterministic. Confirm the per-shot units for your exact dose, vial strength, and frequency in the Testosterone (TRT) dose calculator before drawing, and re-run it whenever the vial concentration or the schedule changes. For the bigger picture of what Testosterone (TRT) is and how it is monitored, start with the complete Testosterone (TRT) guide.

So, what are TRT protocols?

TRT protocols are the frequency patterns that divide a prescribed weekly testosterone dose into individual shots: once-weekly, twice-weekly, every 3.5 days, or daily. The weekly mg stays the same across all protocols — what changes is the per-shot volume, calculated as per-shot mg divided by vial strength (mg/mL), then multiplied by 100 for U-100 units. Confirm the exact draw for your dose, vial concentration, and schedule with the Testosterone (TRT) dose calculator before every injection.

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