How do you dose Testosterone (TRT) every 3 to 5 days? per-shot mg and units

Why split testosterone across 3-to-5-day gaps

Injectable testosterone esters such as cypionate and enanthate are oil-based depots that release slowly and then fade, producing a peak-and-trough curve after every shot. The Hikma cypionate label lists replacement dosing of 50 to 400 mg every two to four weeks, but many modern protocols inject far more often than that to flatten the curve. Shortening the gap to every three to five days is one of the most common ways people do this: the weekly total stays the same, but each individual shot is smaller and the swing between high and low is gentler.

The pharmacokinetic logic is well established. A classic comparison of testosterone enanthate and related depot esters showed serum testosterone rising to a supraphysiological peak within days of an injection and then declining across the dosing interval, which is exactly the curve frequent dosing is meant to smooth. The Endocrine Society guideline frames testosterone therapy around restoring levels into a healthy range with monitoring, not around any single schedule, so the choice of every 3.5, 4, or 5 days is a delivery decision your prescriber makes around a fixed weekly target.

What this page does is purely arithmetic: it turns that weekly target into a per-injection dose and a syringe mark. It does not decide whether Testosterone (TRT) is right for you, what your weekly milligram figure should be, or which ester to use.

How this is calculated

There are two short steps, and both are division. First convert the weekly target into a per-shot dose, then convert that dose into volume and units.

1. Shots per week. Divide 7 by your interval in days. Every 3.5 days is 7 ÷ 3.5 = 2 shots/week. Every 4 days is 7 ÷ 4 = 1.75. Every 5 days is 7 ÷ 5 = 1.4.
2. Per-shot mg. Divide the weekly milligram target by shots per week. 100 mg/week ÷ 2 = 50 mg; 100 ÷ 1.75 = 57 mg; 100 ÷ 1.4 = 71 mg.
3. Volume. Divide per-shot mg by the vial concentration in mg/mL to get milliliters. 50 mg ÷ 200 mg/mL = 0.25 mL.
4. Units. Multiply milliliters by 100 for a U-100 syringe. 0.25 mL × 100 = 25 units.

The thing people miss is that a wider gap does not mean a bigger weekly dose; it means each shot carries a larger slice of the same weekly total. An every-5-day shot is bigger than an every-3.5-day shot for the same prescription, simply because there are fewer of them in the week. Run the same numbers in the Testosterone (TRT) dose calculator whenever you change the interval, the weekly target, or the vial strength.

Per-shot dose by schedule and weekly target

This chart shows the per-injection milligrams for the three most common short-gap schedules. Multiply by your own concentration afterwards to get units.

Notice each row grows left to right: the same weekly target lands a larger per-shot dose as the gap widens, because the week is divided into fewer pieces.

Turning per-shot mg into syringe units

Once you have the per-shot milligrams, the vial concentration decides the syringe mark. The diagram below traces the full path from weekly target to the number you read on the barrel.

Worked examples

Common mistakes

The biggest error is treating a wider interval as a license to inject more in total. Switching from every 3.5 days to every 5 days does not change your weekly milligrams; it only makes each shot larger. If you keep the same per-shot dose while spacing shots further apart, you have quietly cut your weekly total.

The second error is copying a syringe-unit number from someone on a different concentration. 50 units of a 200 mg/mL vial is 100 mg, but 50 units of a 100 mg/mL vial is only 50 mg — same mark, half the dose. Always recalculate units from your own vial strength. A third trap is ignoring dead space, the residue left in the needle hub, which matters more when shots are small. Use clean technique, a fresh sterile needle and syringe, and never use a vial that is cloudy, leaking, or past its date.

So, how do you dose Testosterone (TRT) every 3 to 5 days?

Divide your weekly milligram target by the number of injections that fall in a week to get the per-shot dose, then divide that by your vial concentration and multiply by 100 for syringe units. A 100 mg/week target on an every-3.5-day rhythm is 50 mg per shot — 0.25 mL, or 25 units, from a 200 mg/mL vial. Run your own numbers through the Testosterone (TRT) dose calculator.

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