How many units is 100 mg of testosterone a week?

That question is missing two things: the concentration and the interval. At 200 mg/mL injecting twice weekly, 100 mg a week is 50 mg an injection — 0.25 mL, or 25 units on a U-100 barrel. The same 100 mg a week given once weekly is 50 units in one go, and from a 100 mg/mL vial twice weekly it is 50 units. Same prescription, four different marks on the barrel.

What does 1 unit of testosterone equal in mg?

It depends entirely on what is in the vial, because a unit is a volume and not a dose. A U-100 syringe is graduated so 100 units is exactly 1 mL, so at 200 mg/mL one unit mark delivers 2 mg and at 100 mg/mL it delivers 1 mg. Twenty-five units is 50 mg from a 200 mg/mL vial and 25 mg from a 100 mg/mL one. Read the concentration off the label before you read the barrel.

Is weekly or twice-weekly testosterone injection what the label says?

No, and the distinction matters. The approved cypionate and enanthate oil vials are both labelled at an interval of two to four weeks, and the enanthate label adds that injections more frequently than every two weeks are rarely indicated. Splitting the same weekly milligrams into weekly or twice-weekly injections is ordinary clinical practice, and it is a prescribing decision outside those labels rather than the regimen they describe. One approved product is labelled weekly: XYOSTED, testosterone enanthate in a subcutaneous autoinjector, whose starting dose is 75 mg once a week in the abdomen, supplied at 50, 75 and 100 mg per 0.5 mL.

How long does testosterone cypionate stay in your system?

The Depo-Testosterone label states: “The half-life of testosterone cypionate when injected intramuscularly is approximately eight days.” That is the figure behind the labelled two-to-four-week interval, and it is the reason a fortnightly injection produces a much larger peak and trough swing than the same weekly milligrams split across two. For testosterone enanthate no ester half-life is stated on the label at all — the ten-to-a-hundred-minute figure it gives is the half-life of unesterified testosterone, which is a different quantity — and this page will not quote a number for it that it cannot cite.

What concentration is testosterone supplied in?

Depo-Testosterone is supplied as 100 mg/mL in 10 mL vials and 200 mg/mL in 1 mL and 10 mL vials. The Hikma testosterone enanthate injection is supplied only at 200 mg/mL, in a 5 mL multiple-dose vial. XYOSTED comes as 0.5 mL autoinjectors at 50, 75 and 100 mg. AVEED, testosterone undecanoate, is 750 mg in 3 mL, which is 250 mg/mL, and it is dosed differently from all of the above, so it is not in this calculator.

Can I use an insulin syringe for a testosterone injection?

Volume-wise, most testosterone doses fit: 100 mg from a 200 mg/mL vial is 50 units, half a 1 mL barrel. Whether it is the right instrument is a different question, and not one a calculator answers. The Depo-Testosterone label specifies intramuscular injection deep in the gluteal muscle, and a fixed 29–31G insulin needle at half an inch is both fine enough to make drawing cold oil slow and short enough that it will not reach gluteal muscle in most adults. Route, gauge and needle length belong to your prescriber.

Why does the AVEED dose not fit this calculator?

Because its interval is nothing like a week. The AVEED label states that the recommended dose is 3 mL (750 mg) injected intramuscularly, followed by 3 mL (750 mg) after 4 weeks, then 3 mL (750 mg) every 10 weeks thereafter, given in a healthcare setting with 30 minutes of observation afterwards for pulmonary oil microembolism and anaphylaxis. Expressing that as a weekly milligram figure would be arithmetic with no clinical meaning, and running it through a syringe-unit converter would imply it is something you draw yourself. It is not.

Free dosing tool

Testosterone dose calculator

Turn a weekly milligram dose into the millilitres and U-100 syringe units of a single injection, at your vial’s concentration and your injection interval.

Reviewed by: Alpha Health Finder Editorial Team
Last reviewed: September 2026

Why the weekly dose is never the number on the syringe

Testosterone is prescribed in milligrams a week and injected in millilitres a shot, and the conversion between those two runs through the injection interval before it touches the vial at all. A hundred milligrams a week given twice weekly is fifty milligrams an injection. Given fortnightly it is two hundred. The volume in the barrel differs fourfold between those two protocols for the same prescription, which is why a dose figure copied from a forum post without its interval attached is not a dose figure at all.

Only then does the concentration matter, and it matters a great deal. The approved oil vials come at two strengths — 100 mg/mL and 200 mg/mL — and the same prescribed milligrams is twice the volume from the weaker one. On a U-100 insulin barrel, where 100 units is one millilitre, one unit mark is worth 2 mg at 200 mg/mL and 1 mg at 100 mg/mL. Reading the mark without reading the label is the commonest way a dose comes out double or half.

Interval is a variable here because the esters release at different speeds, and that is a claim the labels support only partly. The Depo-Testosterone label states that testosterone cypionate injected intramuscularly has a half-life of approximately eight days, and that esters in oil are absorbed slowly from the lipid phase, so cypionate can be given at intervals of two to four weeks. The enanthate label states no ester half-life at all — the only half-life it gives, ten to a hundred minutes, is for unesterified testosterone and is a different quantity. This page will not invent the missing figure.

What the labels do say plainly is the interval, and it is longer than almost anyone reading this is on. Depo-Testosterone: 50 to 400 mg every two to four weeks, intramuscular use only, deep in the gluteal muscle. The Hikma enanthate label gives the same range and adds that injections more frequently than every two weeks are rarely indicated. Weekly and twice-weekly splitting of those vials is routine in practice and it is not the labelled regimen; the one approved product that is labelled weekly is XYOSTED, testosterone enanthate in a subcutaneous autoinjector, started at 75 mg once a week. This calculator converts whichever protocol you were actually given. It does not choose one.

The formula

injections per week = 7 ÷ interval (days)

mg per injection = weekly dose (mg) × interval (days) ÷ 7

mL per injection = mg per injection ÷ concentration (mg/mL)

units per injection = mL per injection × 100

and back the other way:

weekly dose (mg) = mg per injection × 7 ÷ interval (days)

The 100 in the third line is not a fudge factor — a U-100 syringe is defined as 100 units to the millilitre, which is the single fact this whole conversion turns on. Units are rounded to the quarter mark because that is the finest a barrel can be read to; one unit is worth 2 mg at 200 mg/mL and 1 mg at 100 mg/mL.

Worked example

100 mg a week, injected twice weekly, from a 200 mg/mL vial:

injections per week = 7 ÷ 3.5 = 2
mg per injection = 100 × 3.5 ÷ 7 = 50 mg
mL per injection = 50 ÷ 200 = 0.25 mL
units per injection = 0.25 × 100 = 25 units on a U-100 barrel
check: 25 units × 2 mg per mark = 50 mg, and 50 mg × 2 = 100 mg a week
the same 100 mg a week from a 100 mg/mL vial is 0.5 mL and 50 units an injection — same dose, twice the volume

Weekly dose split by injection interval — 200 mg/mL vial

Read down for your weekly milligrams, across for how often you inject. The large figure is one injection in milligrams; beneath it is the same injection in U-100 syringe units at 200 mg/mL.

Weekly dose	Every other day3.5×/week	Twice weekly2×/week	Once weekly1×/week	Every 10 days0.7×/week	Every 2 weekslabelled	Every 4 weekslabelled
12.5 mg/wk0.063 mL/wk	3.57 mg1.75 u	6.25 mg3.25 u	12.5 mg6.25 u	17.86 mg9 u	25 mg12.5 u	50 mg25 u
25 mg/wk0.125 mL/wk	7.14 mg3.5 u	12.5 mg6.25 u	25 mg12.5 u	35.71 mg17.75 u	50 mg25 u	100 mg50 u
50 mg/wk0.25 mL/wk	14.29 mg7.25 u	25 mg12.5 u	50 mg25 u	71.43 mg35.75 u	100 mg50 u	200 mg100 u
75 mg/wk0.375 mL/wk	21.43 mg10.75 u	37.5 mg18.75 u	75 mg37.5 u	107.14 mg53.5 u	150 mg75 u	300 mg150 u · luer-lock
100 mg/wk0.5 mL/wk	28.57 mg14.25 u	50 mg25 u	100 mg50 u	142.86 mg71.5 u	200 mg100 u	400 mg200 u · luer-lock
125 mg/wk0.625 mL/wk	35.71 mg17.75 u	62.5 mg31.25 u	125 mg62.5 u	178.57 mg89.25 u	250 mg125 u · luer-lock	500 mg250 u · luer-lock
150 mg/wk0.75 mL/wk	42.86 mg21.5 u	75 mg37.5 u	150 mg75 u	214.29 mg107.25 u · luer-lock	300 mg150 u · luer-lock	600 mg300 u · luer-lock
175 mg/wk0.875 mL/wk	50 mg25 u	87.5 mg43.75 u	175 mg87.5 u	250 mg125 u · luer-lock	350 mg175 u · luer-lock	700 mg350 u · luer-lock
200 mg/wk1 mL/wk	57.14 mg28.5 u	100 mg50 u	200 mg100 u	285.71 mg142.75 u · luer-lock	400 mg200 u · luer-lock	800 mg400 u · luer-lock

Units are on a U-100 insulin barrel, where 100 units is 1 mL; a draw marked “luer-lock” is over a millilitre and will not fit an insulin syringe at all. Only the last two columns are the labelled interval — the Depo-Testosterone and enanthate labels both give 50–400 mg every two to four weeks, and the enanthate label adds that injections more frequently than every two weeks are rarely indicated. The shorter intervals are common clinical practice, charted because people are on them, not because a label describes them.

Weekly dose split by injection interval — 100 mg/mL vial

Read down for your weekly milligrams, across for how often you inject. The large figure is one injection in milligrams; beneath it is the same injection in U-100 syringe units at 100 mg/mL.

Weekly dose	Every other day3.5×/week	Twice weekly2×/week	Once weekly1×/week	Every 10 days0.7×/week	Every 2 weekslabelled	Every 4 weekslabelled
12.5 mg/wk0.125 mL/wk	3.57 mg3.5 u	6.25 mg6.25 u	12.5 mg12.5 u	17.86 mg17.75 u	25 mg25 u	50 mg50 u
25 mg/wk0.25 mL/wk	7.14 mg7.25 u	12.5 mg12.5 u	25 mg25 u	35.71 mg35.75 u	50 mg50 u	100 mg100 u
50 mg/wk0.5 mL/wk	14.29 mg14.25 u	25 mg25 u	50 mg50 u	71.43 mg71.5 u	100 mg100 u	200 mg200 u · luer-lock
75 mg/wk0.75 mL/wk	21.43 mg21.5 u	37.5 mg37.5 u	75 mg75 u	107.14 mg107.25 u · luer-lock	150 mg150 u · luer-lock	300 mg300 u · luer-lock
100 mg/wk1 mL/wk	28.57 mg28.5 u	50 mg50 u	100 mg100 u	142.86 mg142.75 u · luer-lock	200 mg200 u · luer-lock	400 mg400 u · luer-lock
125 mg/wk1.25 mL/wk	35.71 mg35.75 u	62.5 mg62.5 u	125 mg125 u · luer-lock	178.57 mg178.5 u · luer-lock	250 mg250 u · luer-lock	500 mg500 u · luer-lock
150 mg/wk1.5 mL/wk	42.86 mg42.75 u	75 mg75 u	150 mg150 u · luer-lock	214.29 mg214.25 u · luer-lock	300 mg300 u · luer-lock	600 mg600 u · luer-lock
175 mg/wk1.75 mL/wk	50 mg50 u	87.5 mg87.5 u	175 mg175 u · luer-lock	250 mg250 u · luer-lock	350 mg350 u · luer-lock	700 mg700 u · luer-lock
200 mg/wk2 mL/wk	57.14 mg57.25 u	100 mg100 u	200 mg200 u · luer-lock	285.71 mg285.75 u · luer-lock	400 mg400 u · luer-lock	800 mg800 u · luer-lock

The labelled regimen, converted to weekly milligrams

The label is written per injection at a two-to-four-week interval. This is that same regimen expressed as milligrams a week, which is the only form in which it compares with anything else.

Labelled dose	Every 2 weeksmg/week	Every 3 weeksmg/week	Every 4 weeksmg/week
50 mg25 u at 200 mg/mL	25 mg12.5 u/wk	16.67 mg8.25 u/wk	12.5 mg6.25 u/wk
100 mg50 u at 200 mg/mL	50 mg25 u/wk	33.33 mg16.75 u/wk	25 mg12.5 u/wk
150 mg75 u at 200 mg/mL	75 mg37.5 u/wk	50 mg25 u/wk	37.5 mg18.75 u/wk
200 mg100 u at 200 mg/mL	100 mg50 u/wk	66.67 mg33.25 u/wk	50 mg25 u/wk
250 mg125 u at 200 mg/mL	125 mg62.5 u/wk	83.33 mg41.75 u/wk	62.5 mg31.25 u/wk
300 mg150 u at 200 mg/mL	150 mg75 u/wk	100 mg50 u/wk	75 mg37.5 u/wk
400 mg200 u at 200 mg/mL	200 mg100 u/wk	133.33 mg66.75 u/wk	100 mg50 u/wk

Dose amounts are the labelled range for both esters: “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” Across the full window the label spans 12.5 to 200 mg a week. The single-injection unit counts in the left-hand column are the same figures the printable testosterone dosage chart gives for those milligrams, because both are computed by the same function.

Frequently asked questions

How many units is 100 mg of testosterone a week?: That question is missing two things: the concentration and the interval. At 200 mg/mL injecting twice weekly, 100 mg a week is 50 mg an injection — 0.25 mL, or 25 units on a U-100 barrel. The same 100 mg a week given once weekly is 50 units in one go, and from a 100 mg/mL vial twice weekly it is 50 units. Same prescription, four different marks on the barrel.
What does 1 unit of testosterone equal in mg?: It depends entirely on what is in the vial, because a unit is a volume and not a dose. A U-100 syringe is graduated so 100 units is exactly 1 mL, so at 200 mg/mL one unit mark delivers 2 mg and at 100 mg/mL it delivers 1 mg. Twenty-five units is 50 mg from a 200 mg/mL vial and 25 mg from a 100 mg/mL one. Read the concentration off the label before you read the barrel.
What dose does the testosterone label actually state?: The Depo-Testosterone label states: “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” It specifies intramuscular use only, given deep in the gluteal muscle, and requires the diagnosis be confirmed with morning serum testosterone measured on at least two separate days and below the normal range before treatment starts. The Hikma testosterone enanthate label gives the same 50 to 400 mg every 2 to 4 weeks for male hypogonadism. Converted to weekly milligrams that window is 12.5 to 200 mg a week.
Is weekly or twice-weekly testosterone injection what the label says?: No, and the distinction matters. The approved cypionate and enanthate oil vials are both labelled at an interval of two to four weeks, and the enanthate label adds that injections more frequently than every two weeks are rarely indicated. Splitting the same weekly milligrams into weekly or twice-weekly injections is ordinary clinical practice, and it is a prescribing decision outside those labels rather than the regimen they describe. One approved product is labelled weekly: XYOSTED, testosterone enanthate in a subcutaneous autoinjector, whose starting dose is 75 mg once a week in the abdomen, supplied at 50, 75 and 100 mg per 0.5 mL.
How long does testosterone cypionate stay in your system?: The Depo-Testosterone label states: “The half-life of testosterone cypionate when injected intramuscularly is approximately eight days.” That is the figure behind the labelled two-to-four-week interval, and it is the reason a fortnightly injection produces a much larger peak and trough swing than the same weekly milligrams split across two. For testosterone enanthate no ester half-life is stated on the label at all — the ten-to-a-hundred-minute figure it gives is the half-life of unesterified testosterone, which is a different quantity — and this page will not quote a number for it that it cannot cite.
What concentration is testosterone supplied in?: Depo-Testosterone is supplied as 100 mg/mL in 10 mL vials and 200 mg/mL in 1 mL and 10 mL vials. The Hikma testosterone enanthate injection is supplied only at 200 mg/mL, in a 5 mL multiple-dose vial. XYOSTED comes as 0.5 mL autoinjectors at 50, 75 and 100 mg. AVEED, testosterone undecanoate, is 750 mg in 3 mL, which is 250 mg/mL, and it is dosed differently from all of the above, so it is not in this calculator.
Can I use an insulin syringe for a testosterone injection?: Volume-wise, most testosterone doses fit: 100 mg from a 200 mg/mL vial is 50 units, half a 1 mL barrel. Whether it is the right instrument is a different question, and not one a calculator answers. The Depo-Testosterone label specifies intramuscular injection deep in the gluteal muscle, and a fixed 29–31G insulin needle at half an inch is both fine enough to make drawing cold oil slow and short enough that it will not reach gluteal muscle in most adults. Route, gauge and needle length belong to your prescriber.
Why does the AVEED dose not fit this calculator?: Because its interval is nothing like a week. The AVEED label states that the recommended dose is 3 mL (750 mg) injected intramuscularly, followed by 3 mL (750 mg) after 4 weeks, then 3 mL (750 mg) every 10 weeks thereafter, given in a healthcare setting with 30 minutes of observation afterwards for pulmonary oil microembolism and anaphylaxis. Expressing that as a weekly milligram figure would be arithmetic with no clinical meaning, and running it through a syringe-unit converter would imply it is something you draw yourself. It is not.

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Compare online TRT providersTelehealth platforms that prescribe, dispense and monitor, with what each plan includes.Print the dosage chartThe same conversions as a one-page table you can keep beside the vial.

Related calculators

Educational reference, not medical advice. This converts a dose someone has already prescribed; it does not select one, and no figure on this page is a recommended dose. The labelled regimen for the oil vials is narrower than most protocols in use: “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” — intramuscular only, deep in the gluteal muscle, after the diagnosis has been confirmed with morning serum testosterone measured on at least two separate days and below the normal range. Weekly and twice-weekly splitting is common clinical practice, not the labelled interval, and the only approved once-weekly product is XYOSTED, a subcutaneous autoinjector, not a vial. Check the concentration printed on your own vial before you draw: at 200 mg/mL a unit mark is 2 mg and at 100 mg/mL it is 1 mg, so reading the barrel without reading the label is how a dose comes out double.