Oil-carrier dosing
Testosterone is pre-mixed.
Oil-suspended compounds arrive at a stated concentration, so there is no reconstitution. What remains is the gap between milligrams and syringe units.
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The science
Concentration is printed, not calculated
01
A vial labelled 200 mg/ml is already at its final concentration. Unlike a lyophilised peptide there is nothing to reconstitute, which removes the first and most error-prone step of the arithmetic.
02
What remains is dividing the weekly dose across your injection frequency, then converting that per-injection dose into volume and volume into units. A weekly 140 mg split twice is 70 mg per injection; at 200 mg/ml that is 0.35 ml, which is 35 units on a U-100 syringe.
03
Splitting the weekly dose across more frequent injections keeps blood levels steadier than a single large weekly dose, which is why twice weekly and every-other-day schedules are common. How often to inject is a clinical decision rather than a matter of convenience.
04
Oil is considerably more viscous than water. Drawing through a narrow insulin needle is slow and can introduce air, so a common approach is a wider needle to draw and a finer one to inject. Warming the vial slightly in the hand also helps it move.
FAQ
Common questions
How many units is 100 mg of testosterone?
It depends entirely on the concentration. At 200 mg/ml, 100 mg is 0.5 ml, which is 50 units on a U-100 syringe. At 100 mg/ml the same dose is 1 ml, or 100 units.
Can I use an insulin syringe for TRT?
Many people do for subcutaneous injection, because the unit markings measure small volumes accurately. Oil draws slowly through a narrow needle, so drawing with a wider needle and injecting with a finer one is common practice.
Why split the weekly dose?
More frequent, smaller injections keep blood levels steadier than one large weekly dose. The right frequency is a clinical decision for your prescriber.
Is this calculator specific to testosterone?
No. It works for any compound supplied pre-mixed at a stated mg/ml, which includes most oil-carrier preparations.
What concentrations does testosterone come in?
Commonly 100, 200 or 250 mg/ml for the various esters. The concentration is printed on the vial and is the single most important number for this calculation.
Why does my dose need so many units?
Because the concentration is low relative to your dose. A 100 mg/ml vial needs twice the volume of a 200 mg/ml vial for the same dose. If the volume exceeds your syringe, a higher-concentration vial solves it.
VialClock
This page calculates. Your notes app forgets.
Every tool here is stateless by design. What it cannot do is remember that your vial was mixed eleven days ago, or that a step-up is due this week.
Browse all calculatorsThis tool performs arithmetic on figures you enter, or presents a manufacturer-published schedule. It does not know your protocol, will never suggest a dose, and is not medical advice. Dosing decisions belong with a qualified prescriber.