Injection schedule planner

Why an interval is harder than it looks on a calendar

A prescription is written in milligrams a week. A syringe carries one injection. Between those two sits the interval, and it changes the number in the barrel fourfold without changing the prescription at all: a hundred milligrams a week is fifty milligrams an injection given twice weekly and two hundred given fortnightly. That step is where doses double, and it happens before the vial concentration is even involved.

Then the interval has to become dates, and this is where a figure that looks tidy stops being tidy. "Twice weekly" is 3.5 days, and there is no such thing as half a day on a calendar. A schedule built by repeatedly adding three and a half days and rounding as it goes drifts — by the tenth injection it is a day or two from where the arithmetic says it should be, and the error is invisible because each individual step looked right. This planner computes every date from the FIRST injection instead, so the nth injection is always within half a day of n times the interval however far out you run it. What you get back is an alternation rather than a slide: a Monday start gives Monday and Thursday, with gaps of three days and four days, repeating exactly every seven days. The planner prints that gap pattern rather than hiding it behind a decimal.

Only then does the vial matter. The approved oil vials come at two strengths, and the same prescribed milligrams is twice the volume from the weaker one. On a U-100 insulin barrel, where 100 marks is one millilitre, one mark is worth 2 mg at 200 mg/mL and 1 mg at 100 mg/mL. The calendar below carries the millilitres and the marks for every dated injection so the two numbers never have to be held in your head at once.

What none of this is, is a regimen. A calendar is a persuasive object — a dated list reads as something a clinician signed off — so it is worth being blunt about what the labels describe. Both approved testosterone oil vials state 50 to 400 mg every two to four weeks for replacement in the hypogonadal male, and the enanthate label adds "Injections more frequently than every two weeks are rarely indicated." Weekly and twice-weekly splitting of those vials is routine in clinics and is a prescribing decision outside those labels. Exactly one approved product is labelled weekly — XYOSTED, testosterone enanthate in a sealed subcutaneous autoinjector at 50, 75 or 100 mg per 0.5 mL — and naming it is not the same as using it to cover a weekly vial protocol, because you cannot split a vial into an autoinjector. Every table on this page marks each interval as labelled, XYOSTED-only or practice. This tool lays out whichever schedule you were actually given; it does not choose one.

Twelve injections on the calendar — 100 mg a week, twice weekly, 200 mg/mL

The commonest protocol in practice, dated from a Monday start. Every figure is computed, including the dates; the amount per injection never changes, only the day does.

Look at the gap column: 3 then 4 days, alternating, landing on Mon and Thu every week. That is what a 3.5-day interval is on a calendar — there is no half day, so the pattern alternates rather than drifting, and every date here is measured from the first injection rather than added to the last. Common clinical practice, not a labelled interval. No approved testosterone vial label describes this frequency.

The same 100 mg a week, on seven different intervals

One prescription, one start date, one vial strength. The only thing that changes is how often — and it changes the amount in the barrel eightfold across these columns.

Columns marked "practice" are what most readers are on and no label describes them. "labelled" is the two-to-four-week window both approved oil vials state: “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” The once-weekly column is marked "XYOSTED only" because weekly is on exactly one approved label — “The starting dose of XYOSTED is 75 mg, administered subcutaneously in the abdominal region once a week.” — and that product is a sealed 0.5 mL autoinjector, not a vial you can split a weekly dose into. Six injections is six injections on every column, so the rightmost column spans five months and the leftmost ten days; that is the interval doing its work, not an error.

What each interval does to the days of the week

Whether a schedule settles onto fixed weekdays or walks around the calendar, and where the alternating gaps come from.

Only an interval that divides seven, or that seven divides, keeps the same weekdays. Every other day and every ten days both walk forward through the week, which matters more than it sounds: a schedule with no fixed weekday is one you cannot keep in your head, and a missed injection on it is invisible. Where the gap column shows two numbers the interval is not a whole number of days and the calendar alternates between them; the average is exactly the interval you asked for.

Amount per injection, and how long a vial lasts

Read down for your weekly milligrams, across for how often you inject. Beneath each amount is the U-100 mark count and how many injections a 10 mL vial at 200 mg/mL holds.

Every milligram and mark figure here is produced by the same function as /tools/testosterone-dose-calculator and /charts/testosterone-dosage-chart, so all three agree by construction. "luer-lock" means one injection is over a millilitre and no insulin barrel takes it. Note that the injections-per-vial figure changes across a row while the vial's LIFE does not: a 10 mL vial at 200 mg/mL holds 2,000 mg however you slice it, so at 100 mg a week it is twenty weeks whether that is twenty injections or forty. What the interval changes is the size of each draw, not the supply. A pharmacy may also set a beyond-use date once a multiple-dose vial is entered, which can bite long before the volume runs out.

What the approved labels actually schedule

The four injectable testosterone products and the interval each label states. Nothing here is converted into a protocol; it is what the documents say.

The last row is on this table on purpose. It is the schedule the calendar at the top of this page lays out and the one most readers arrive with, and it does not appear on any approved label — which is a statement about the documents, not about whether it is reasonable. AVEED is the only product whose schedule this page will not plan: “The recommended dose of AVEED is 3 mL (750 mg) injected intramuscularly, followed by 3 mL (750 mg) injected after 4 weeks, then 3 mL (750 mg) injected every 10 weeks thereafter.” It is given in a certified healthcare setting with 30 minutes of observation after every injection under a Risk Evaluation and Mitigation Strategy, so a self-service calendar for it would imply something untrue.

Frequently asked questions

What days should I inject if I inject twice a week?

Twice weekly is 3.5 days, and a calendar has no half days, so the honest answer is a pair of weekdays with alternating gaps rather than a single number. From a Monday start this planner gives Mon and Thu, with gaps of 3 and 4 days, repeating exactly every seven days — Monday, Thursday, Monday, Thursday. Any pair three and four days apart does the same job; what matters is that the pattern repeats weekly so the day of the week carries the reminder. The planner measures every date from the first injection rather than adding to the last, which is why the twelfth injection lands on day 38 exactly instead of a day or two adrift.

How much do I inject if my dose is 100 mg a week?

That question is missing the interval and the concentration, and both change the answer. At 200 mg/mL injecting twice weekly, 100 mg a week is 50 mg an injection — 0.25 mL, or 25 marks on a U-100 barrel. The same 100 mg a week given once weekly is 50 marks in one go, and given fortnightly it is 100. From a 100 mg/mL vial every one of those volumes doubles. Same prescription, six different marks on the barrel — which is why a dose copied from a forum post without its interval and its concentration attached is not a dose at all.

Is a weekly or twice-weekly injection schedule what the label says?

No, and the distinction is worth holding onto. Both approved testosterone oil vials are labelled at an interval of two to four weeks — “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” — and the enanthate label adds “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 is a prescribing decision outside those labels rather than the regimen they describe. One approved product is labelled weekly and it is not a vial: “The starting dose of XYOSTED is 75 mg, administered subcutaneously in the abdominal region once a week.” XYOSTED is a sealed 0.5 mL autoinjector supplied at 50, 75 and 100 mg, so it is an exception to name rather than a precedent to borrow. Every table on this page marks each interval as labelled, XYOSTED-only or practice.

If I miss an injection, do I shift the whole schedule?

This planner will not answer that, and the reason is that no label it is built from does either. The approved cypionate, enanthate and XYOSTED labels contain no missed-dose instruction — there is nothing to quote and nothing to compute. What the planner can tell you is what the schedule was: every date is anchored to the first injection, so if you move one injection the following dates in the table are still the original plan rather than a re-based one. A missed injection is a conversation with whoever prescribed it, particularly on a fortnightly or monthly interval where one gap is a large fraction of the whole cycle.

How long will a 10 mL vial last at my interval?

Longer than most people expect, and the interval does not change it. A 10 mL vial at 200 mg/mL holds 2,000 mg, so at 100 mg a week it is twenty weeks whether you take that as 20 weekly injections of 50 marks or 40 twice-weekly injections of 25. Splitting more often makes each draw smaller and the arithmetic per injection finer; it does not consume more or less drug. The real limit is often not volume at all — a pharmacy sets a beyond-use date once a multiple-dose vial is entered, and that date can arrive well before the vial empties.

Why does the calendar put a three-day gap and then a four-day gap?

Because 3.5 days is not a number of days you can put on a calendar, and something has to give. The planner computes each date as round((n − 1) × 3.5) measured from the first injection, which produces offsets of 0, 3, 7, 10, 14 and so on — gaps of three, four, three, four, averaging exactly 3.5. The alternative, adding 3.5 days each time and rounding as you go, drifts: each step looks right and the tenth injection is on the wrong day. At exactly half a day the rounding goes down, so a Monday start gives Monday and Thursday rather than Monday and Friday. That is a tie-break in the arithmetic, not a clinical preference.

Can I plan an AVEED schedule with this?

No, and the omission is deliberate. AVEED is testosterone undecanoate, 750 mg in 3 mL, and its label states: “The recommended dose of AVEED is 3 mL (750 mg) injected intramuscularly, followed by 3 mL (750 mg) injected after 4 weeks, then 3 mL (750 mg) injected every 10 weeks thereafter.” It is given intramuscularly in a certified healthcare setting, and after every injection the patient is observed there for 30 minutes so that serious pulmonary oil microembolism reactions or anaphylaxis can be treated — reactions that can follow any dose including the first. Because of those risks AVEED is available only through a restricted programme under a Risk Evaluation and Mitigation Strategy. Printing a self-service calendar for it would imply it is something you administer on a schedule of your own, and it is not.

Does injecting more often change how much drug I get?

Not in total, no — that is what the arithmetic says and it is worth being precise about. A hundred milligrams a week is a hundred milligrams a week at every interval on this page; splitting it changes the size of each injection and nothing else. At 200 mg/mL that is 14.25 marks every other day, 25 marks twice weekly, 50 marks once weekly or 200 marks every four weeks. What splitting does change is the peak-to-trough swing between injections, and the labels support that claim only partly: the cypionate label states a half-life of approximately eight days, while neither enanthate label states an ester half-life at all. This page will not put a number on a difference one of its labels does not publish.

Sources

1. [1]FDA label — DEPO-Testosterone (testosterone cypionate injection, USP), Pharmacia & Upjohn Company LLC. DailyMed SPL cfbb53d4-b868-4a28-8436-f9112eb01c39, approval block ANDA 085635, SPL version 26, effective 2026-08-21. Source of “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.”, the intramuscular-only and deep-gluteal directions, the two-morning-tests requirement, the 100 and 200 mg/mL strengths and the 1 mL and 10 mL vials
2. [2]FDA label — Testosterone Enanthate Injection, USP 200 mg/mL, Hikma Pharmaceuticals USA Inc. DailyMed SPL e89d6458-428c-4256-97a3-f1fa851293c1, approval block ANDA 091120, SPL version 10, effective 2026-05-08. Source of “Male hypogonadism: As replacement therapy, i.e., for eunuchism, the suggested dosage is 50 to 400 mg every 2 to 4 weeks.”, “In general, total doses above 400 mg per month are not required because of the prolonged action of the preparation. Injections more frequently than every two weeks are rarely indicated.” and the 5 mL multiple-dose vial
3. [3]FDA label — XYOSTED (testosterone enanthate) injection, for subcutaneous use, Antares Pharma, Inc. DailyMed SPL 8a3d204c-be26-49e0-8599-0ac12a272e81, approval block NDA 209863, SPL version 16, effective 2025-07-01. The one approved product labelled weekly. Source of “The starting dose of XYOSTED is 75 mg, administered subcutaneously in the abdominal region once a week.”, the 25 mg adjustment steps, the 350–650 ng/dL trough window and the three 0.5 mL strengths
4. [4]FDA label — AVEED (testosterone undecanoate) injection, for intramuscular use, Endo USA, Inc. DailyMed SPL f80f025b-17d8-40af-8739-20ce07902045, approval block NDA 022219, SPL version 45, effective 2025-07-15. Source of the every-ten-week regimen this planner declines to schedule, the boxed warning, the 30-minute observation requirement and the AVEED REMS Program
5. [5]Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744