How long does a 10 mL vial of testosterone last?

At 100 mg once a week, a 10 mL vial at 200 mg/mL is 20 injections and 140 days — 2,000 mg divided by 100. The same vial at 100 mg/mL is half that: 10 injections and 70 days. A year of weekly injections at 100 mg takes 3 vials of the 200 mg/mL. What no approved label will tell you is whether the vial is still good after all those weeks: seven testosterone cypionate labels were searched and none states a discard date after first puncture.

How many doses are in an Ozempic pen, and how long does it last?

Section 3 of the label states it rather than leaving it to arithmetic: “2 mg/3 mL (0.68 mg/mL) for 4 doses of 0.25 mg and 2 doses of 0.5 mg or 4 doses of 0.5 mg, 4 mg/3 mL (1.34 mg/mL) for 4 doses of 1 mg, and 8 mg/3 mL (2.68 mg/mL) for 4 doses of 2 mg”. Four weekly injections is 28 days. The pen’s in-use clock runs longer than that — “After first use of the OZEMPIC pen, the pen can be stored for 56 days” — so on a weekly schedule the drug always runs out first and the 56 days never binds. The Instructions for Use are blunt about which way the rule points if it ever did: “The OZEMPIC pen you are using should be disposed of (thrown away) after 56 days, even if it still has OZEMPIC left in it.”

Is a Wegovy pen four doses?

That depends entirely on which Wegovy you were dispensed, and the two are different products in the same carton design. The standard presentation is a SINGLE-dose pen — the carton reads “4 Single-Dose Prefilled Pens. Each pen delivers a single dose of 0.25 mg semaglutide”, so it is the CARTON that is four weeks, not the pen, and the label says “Discard the WEGOVY pen or syringe after use.” There is also a WEGOVY FlexTouch single-patient-use pen, “9.6 mg/3 mL (3.2 mg/mL) solution in a single-patient-use pen (WEGOVY FlexTouch) that delivers four 2.4 mg/0.75 mL doses”, and that one genuinely is four doses in one device, with a 56-day clock after first use. If you are counting what is left, check which of the two you are holding first.

How long does a Zepbound vial last after you open it?

ZEPBOUND is the one label on this page that states three ceilings in a single sentence and tells you to take whichever arrives first: “Throw away opened multi-dose vial or single-patient-use KwikPen after a total of 30 days at room temperature, 30 days after first use, or after taking 4 weekly doses, even if there is medicine left in it.” Four weekly doses is 28 days, so on a weekly schedule the dose count runs out two days before the 30-day clock and the drug runs out at the same moment — the 2.4 mL vial is built to hold exactly four. The single-dose pen and single-dose vial are a different question with a different answer: one dose, and a 21-day allowance out of the refrigerator before use, not after it.

How long does a reconstituted peptide vial last?

For an unapproved peptide, nobody has established that and we will not print a figure. A beyond-use date comes from stability testing of one formulation in one container, and no such data has been published for BPC-157, ipamorelin, retatrutide or the rest — so a number quoted to you has been borrowed from a different drug. For licensed peptides the figure exists and it is short and specific, which is the point: EGRIFTA WR is “Discard unused solution of EGRIFTA WR vial 7 days after mixing”, SEROSTIM 4 mg in bacteriostatic water “may be refrigerated at 2°C to 8°C (36°F to 46°F) for up to 14 days”, NOVAREL “should be refrigerated and used within 30 days” and PREGNYL is “STABLE FOR 60 DAYS WHEN REFRIGERATED”. Seven days to sixty, all FDA labels. There is no default to fall back on.

Why does my pen still have medicine in it when the label says to throw it away?

Because the two ceilings rarely land on the same day, and the label is written to the shorter one. A SAXENDA pen at 3 mg daily holds 6 doses — 6 days — inside a 30-day window, so it empties long before the clock. Run the same pen at a smaller daily dose and it inverts: the drug would give more days than the pen is allowed, and the remainder is discarded. EGRIFTA WR is the extreme case on this page — the reconstituted vial deliverably holds 8 daily doses but the label allows 7, so 1.44 mg is thrown away by instruction. Only one configuration here wastes nothing: a SAXENDA pen at 0.6 mg, where 30 doses and a 30-day clock expire together.

My testosterone vial holds 20 weeks of drug but CDC says 28 days — which is it?

Both figures are right and they are answers to different questions, which is exactly why this is the most-asked version of it. 2,000 mg at 100 mg a week is 20 injections and 140 days of DRUG — that is arithmetic and it is not in dispute. CDC’s 28 days is a general infection-control rule for any punctured multi-dose vial, stated with an explicit escape clause: discard “within 28 days unless the manufacturer states another date for that opened vial”. Here no manufacturer states another date — we searched seven approved testosterone cypionate labels and found no post-puncture language of any kind — so the escape clause never opens and the general rule is all there is. This page will not adjudicate that for you, because no FDA label does. What it will do is show you both numbers instead of quietly printing whichever one you were hoping for. Your prescriber and your pharmacy are the people who can tell you which applies to the vial you were dispensed.

How many testosterone vials do I need for a year?

3 vials at 100 mg once a week, if you buy the 10 mL 200 mg/mL presentation: each vial is 140 days, and 365 days divided by 140 rounds up to 3. On the 100 mg/mL vial the same prescription takes 6. Round up rather than down — running out mid-course is the expensive error, and the leftover is a spare vial. This is a count of containers, not a cost: /tools/trt-cost-calculator puts a sourced acquisition price against the same arithmetic.

Arithmetic, and the dates no label gives

Vial duration calculator

A container ends when the drug runs out or when the clock that started at first puncture runs out — whichever comes first. This works out both, for testosterone, GLP-1 pens and reconstituted vials, and says plainly where no clock exists.

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

Two ceilings, and the one people forget is on the calendar

Everybody does the first division. Drug in the container, divided by drug in one injection, rounded down, multiplied by the days between injections. A 10 mL vial at 200 mg/mL holds 2,000 mg; at 100 mg once a week that is 20 injections and 140 days. The same vial at 100 mg/mL holds half that and lasts 70 days. That part is not hard and it is not where people go wrong.

The part that is missed is that a punctured container is also on a clock, and the clock does not care how much is left. OZEMPIC states it as bluntly as a label ever states anything: “The OZEMPIC pen you are using should be disposed of (thrown away) after 56 days, even if it still has OZEMPIC left in it.” ZEPBOUND stacks three limits in a single sentence — “Throw away opened multi-dose vial or single-patient-use KwikPen after a total of 30 days at room temperature, 30 days after first use, or after taking 4 weekly doses, even if there is medicine left in it.” Whichever ceiling is lower is your answer, and which one that is changes by product.

It genuinely flips. An OZEMPIC 8 mg pen at the 2 mg maintenance dose holds 4 weekly injections — 28 days — against a 56-day clock, so the drug always runs out first and the clock never binds. A SAXENDA pen at the 0.6 mg starting dose holds 30 daily doses against a 30-day clock, so the two expire on the same morning and nothing is wasted. The same pen at the 3 mg maintenance dose is 6 days of drug inside a 30-day window, so the drug wins again — but below 0.6 mg a day the arithmetic inverts and the clock would start throwing medicine away — which is the situation nobody budgets for, and not a suggestion that anyone should be dosing there.

And the labels that state a clock do not agree with each other. Among the ones quoted on this page: EGRIFTA WR is discarded 7 days after mixing, SEROSTIM 4 mg may be refrigerated for 14, ZEPBOUND’s opened multi-dose vial and SAXENDA’s pen and NOVAREL’s reconstituted solution all run to 30, OZEMPIC and WEGOVY FlexTouch to 56, and PREGNYL’s reconstituted solution to 60. There is no general figure hiding behind those. They are seven different stability programmes on seven different formulations.

Which brings us to the number that is not on any of them. The 28 days everyone quotes is real and worth following, but it is not a label figure: it is CDC, citing USP General Chapter <797> — “Once a multi-dose vial is opened (e.g., needle-punctured) the vial should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.” We went looking for it on the labels of the container men’s health punctures most. Seven approved testosterone cypionate labels — Pharmacia & Upjohn’s Depo-Testosterone, Hospira, Cipla, Hikma, Sun, Eugia and Xiromed — retrieved as XML and searched on 20 September 2026 for “discard”, “punctur”, “beyond”, “in-use” and “28 day”. All five strings occur zero times in all seven. Every one of them says the same single thing about storage and nothing more: “Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Protect from light.”

So this page will tell you how many injections are in your vial, and it will tell you what your product’s label says about the calendar where a label says anything. Where no label says anything — an opened testosterone vial, a bottle of bacteriostatic water, a compounded GLP-1, any unapproved peptide — it says so, and it does not quietly substitute CDC’s 28. Date the vial at first puncture and follow the 28-day rule if you have nothing better; just do not tell yourself the vial told you to.

The formula

doses from the drug = floor(total mg in container ÷ mg per injection)

days from the drug = doses from the drug × days between injections

doses the clock allows = floor(in-use days ÷ days between injections)

doses you actually get = the SMALLER of those two

days of supply = doses you actually get × days between injections

2,000 mg ÷ 100 mg = 20 injections × 7 days = 140 days, no clock stated

Doses are floored in both directions: part of an injection is not an injection, and a dose falling exactly on the discard date is not counted. That second choice is an editorial one and worth naming — a pen first used on day 0 and discarded at 56 days could be argued to carry a weekly dose ON day 56, making nine rather than eight. No label resolves it, so this page takes the shorter reading, because being one dose out in that direction wastes a dose and being one out in the other means injecting from a container the label says to throw away. Containers needed for a period are rounded UP, for the opposite reason: the error of buying one too many is a spare vial.

Worked example

A 10 mL vial of testosterone cypionate at 200 mg/mL, with a prescription for 100 mg once a week:

Drug in the vial = 10 mL × 200 mg/mL = 2,000 mg
Injections in the vial = 2,000 mg ÷ 100 mg = 20, with 0 mg left over
Days of supply = 20 × 7 days = 140 days, about 20 weeks
In-use clock: none. No approved testosterone cypionate label states a discard date after first puncture
So the binding constraint is the drug — no clock exists — and a year of this takes 3 vials

How long a testosterone cypionate vial lasts

Days of supply from each labelled Depo-Testosterone presentation at a weekly injection. No approved testosterone label states an in-use clock, so every figure here is the drug running out.

Weekly dose	100 mg/mL, 10 mL1,000 mg · multiple-dose	200 mg/mL, 10 mL2,000 mg · multiple-dose	200 mg/mL, 1 mL200 mg · single-dose
50 mgonce a week	140 days20 injections	280 days40 injections	7 days1 injection · 150 mg unused
75 mgonce a week	91 days13 injections · 25 mg unused	182 days26 injections · 50 mg unused	7 days1 injection · 125 mg unused
100 mgonce a week	70 days10 injections	140 days20 injections	7 days1 injection · 100 mg unused
125 mgonce a week	56 days8 injections	112 days16 injections	7 days1 injection · 75 mg unused
150 mgonce a week	42 days6 injections · 100 mg unused	91 days13 injections · 50 mg unused	7 days1 injection · 50 mg unused
200 mgonce a week	35 days5 injections	70 days10 injections	7 days1 injection

The three columns are the only presentations the Depo-Testosterone label lists: “100 mg/mL 10 mL vials NDC 0009-0347-02 / 200 mg/mL 1 mL vials NDC 0009-0417-01 / 10 mL vials NDC 0009-0417-02”. The 1 mL column is short because its carton reads “One 1 mL Vial Single-dose” — the label permits one entry, so anything left after one injection is discarded by the labelling rather than by choice, and the “unused” figure in those cells is what the label throws away. The weekly doses down the side are an arithmetic axis and not a recommendation: the label’s own statement is for a different interval altogether — “For replacement in the hypogonadal male, 50 - 400 mg should be administered every two to four weeks.” What is NOT in this table is a discard date for an opened 10 mL vial, because no approved testosterone cypionate label states one. See the next chart.

What each label says about the clock — and where it says nothing

The in-use period from first puncture, product by product. Eight labels state one and they state eight different things; five containers have no published figure at all.

Container	Days from first use	Where that figure comes from	Doses the label caps it at
EGRIFTA WR (tesamorelin)11.6 mg vial, reconstituted	7 daysstated on the label	FDA-approved label	None stated
SEROSTIM (somatropin)4 mg vial, reconstituted	14 daysstated on the label	FDA-approved label	None stated
ZEPBOUND (tirzepatide)Multi-dose vial or KwikPen, 2.4 mL	30 daysstated on the label	FDA-approved label	4 doses
SAXENDA / VICTOZA (liraglutide)18 mg/3 mL prefilled pen	30 daysstated on the label	FDA-approved label	None stated
NOVAREL (chorionic gonadotropin)10,000 unit vial, reconstituted	30 daysstated on the label	FDA-approved label	None stated
OZEMPIC (semaglutide)Single-patient-use pen, 3 mL	56 daysstated on the label	FDA-approved label	None stated
WEGOVY FlexTouch (semaglutide)Single-patient-use pen, 9.6 mg/3 mL	56 daysstated on the label	FDA-approved label	None stated
PREGNYL (chorionic gonadotropin)10 mL multiple-dose vial, reconstituted	60 daysstated on the label	FDA-approved label	None stated
WEGOVY (semaglutide)Single-dose pen or syringe	One use onlythe container is spent	FDA-approved label	1 dose
Testosterone cypionate10 mL multiple-dose vial	Not statedthe label is silent	Nowhere — the label is silent	None stated
Bacteriostatic Water, USP30 mL multiple-dose vial	Not statedthe label is silent	Nowhere — the label is silent	None stated
Compounded semaglutide or tirzepatidePharmacy-filled vial	Set by the pharmacyread their label	The compounder’s label	None stated
Unapproved peptideLyophilised vial, reconstituted	None establishedno stability data exists	Nowhere — none published	None stated

Read the bottom four rows as findings rather than gaps. Testosterone cypionate: seven approved labels retrieved as XML and searched on 20 September 2026 — “discard”, “punctur”, “beyond”, “in-use” and “28 day” occur zero times in all seven. Bacteriostatic water: all seven standalone Bacteriostatic Water for Injection, USP labels on DailyMed were searched for the same strings when /charts/bac-water-mixing-chart was built and the Hospira label was re-checked here; the water does not answer the question, it hands it over — “Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.” Compounded GLP-1: not FDA-approved, so there is no FDA-reviewed label to read; the beyond-use date is the compounding pharmacy’s and is printed on their vial. Unapproved peptides: a beyond-use date requires stability testing of a specific formulation in a specific container, and none has been published for any of them, so we print none — anyone quoting you 28 or 56 days for BPC-157 is quoting it off a different drug. What you have instead for all four is CDC, citing USP General Chapter <797>: date the vial at first puncture and discard within 28 days “unless the manufacturer states another date for that opened vial”, and never past the printed expiry.

Which ceiling ends the container first

The same container measured twice — once by the drug in it and once by the label’s clock — at the dose each product is actually used at. The lower figure is the real answer.

Container and dose	Doses in itfrom the drug	Days from the drug	Days the clock allows	Days of supplythe lower of the two	Which ends it
OZEMPIC 8 mg/3 mL pen2 mg once weekly	4	28 days	56 days	28 daysnothing wasted	The drug
WEGOVY FlexTouch pen2.4 mg once weekly	4	28 days	56 days	28 daysnothing wasted	The drug
ZEPBOUND multi-dose vial10 mg once weekly	4	28 days	30 days	28 daysnothing wasted	All three, together
SAXENDA 18 mg/3 mL pen0.6 mg once daily	30	30 days	30 days	30 daysnothing wasted	Both, together
SAXENDA 18 mg/3 mL pen3 mg once daily	6	6 days	30 days	6 daysnothing wasted	The drug
EGRIFTA WR, reconstituted1.28 mg once daily	8	8 days	7 days	7 days1.44 mg cannot be used	The clock
Testosterone cypionate 10 mL100 mg once weekly, 200 mg/mL	20	140 days	Not stated	140 daysnothing wasted	The drug — no clock exists
Unapproved peptide, 10 mg vialany 0.5 mg draw — see footnote	20	140 days	None established	Not determinablemass alone gives 140 days	Unknown — no date exists

Three rows are worth reading twice. SAXENDA at 0.6 mg is the one configuration on this page where both ceilings land on the same day — 30 daily doses and a 30-day pen — so nothing is thrown away; at 3 mg the same pen is 6 days of drug and the 30-day window never comes into it. EGRIFTA WR is the reverse and the clearest case of the clock winning: the vial deliverably holds 8 daily doses of 1.28 mg but the label says “One reconstituted vial provides daily doses for 7 days. Discard unused solution of EGRIFTA WR vial 7 days after mixing”, so 1.44 mg goes in the bin on day seven. Its mass is taken as the label’s deliverable 8 mg/mL × 1.3 mL rather than the 11.6 mg printed on the vial, because the overfill is not dose. The last two rows are where the page stops rather than guesses. Testosterone is the widest divergence on the site: 2,000 mg at 100 mg a week is 140 days of drug, while CDC’s general multi-dose-vial rule would have you date the vial at first puncture and discard it at 28 days with roughly three quarters of it still in the glass. No approved testosterone label adjudicates that, because none of the seven says anything at all about the calendar — so this page prints the drug figure, names CDC’s rule as CDC’s, and does not pretend the conflict is settled. The peptide row prints no days-of-supply figure at all: with no beyond-use date established, the mass division is not an answer to how long the vial lasts, and the 0.5 mg in that row is an arithmetic input chosen to show the division, not a dose. No dose for any unapproved peptide is established and this page does not supply one.

Doses in a vial, for any vial and any draw

The mass division on its own, for a reconstituted or compounded vial where no clock is published. Weeks assume one injection a week.

Drug in the vial	0.5 mgper injection	1 mgper injection	2.5 mgper injection	5 mgper injection	10 mgper injection
5 mgwhatever the diluent	10 doses70 days weekly	5 doses35 days weekly	2 doses14 days weekly	1 dose7 days weekly	Under one doseneeds two vials
10 mgwhatever the diluent	20 doses140 days weekly	10 doses70 days weekly	4 doses28 days weekly	2 doses14 days weekly	1 dose7 days weekly
15 mgwhatever the diluent	30 doses210 days weekly	15 doses105 days weekly	6 doses42 days weekly	3 doses21 days weekly	1 dose7 days weekly
20 mgwhatever the diluent	40 doses280 days weekly	20 doses140 days weekly	8 doses56 days weekly	4 doses28 days weekly	2 doses14 days weekly
30 mgwhatever the diluent	60 doses420 days weekly	30 doses210 days weekly	12 doses84 days weekly	6 doses42 days weekly	3 doses21 days weekly
40 mgwhatever the diluent	80 doses560 days weekly	40 doses280 days weekly	16 doses112 days weekly	8 doses56 days weekly	4 doses28 days weekly
60 mgwhatever the diluent	120 doses840 days weekly	60 doses420 days weekly	24 doses168 days weekly	12 doses84 days weekly	6 doses42 days weekly

Two things this grid deliberately does not have. There is no diluent column, because the water makes no difference: reconstitution does not change the drug mass, so a 10 mg vial holds the same twenty 0.5 mg doses in 1 mL as in 5 mL — only the volume you draw changes, and /tools/peptide-reconstitution-calculator turns that into a mark on the barrel. And there is no days-until-discard column, because for a compounded or unapproved vial nobody has published one; the compounder’s own beyond-use date, printed on their label, is the only figure that exists and it overrides everything here. The doses along the top are arithmetic inputs. They are not a protocol, they are not sourced from a trial, and this page does not tell you which of them, if any, applies to anything.

Frequently asked questions

How long does a 10 mL vial of testosterone last?: At 100 mg once a week, a 10 mL vial at 200 mg/mL is 20 injections and 140 days — 2,000 mg divided by 100. The same vial at 100 mg/mL is half that: 10 injections and 70 days. A year of weekly injections at 100 mg takes 3 vials of the 200 mg/mL. What no approved label will tell you is whether the vial is still good after all those weeks: seven testosterone cypionate labels were searched and none states a discard date after first puncture.
How long is testosterone good for after you open the vial?: No FDA-approved testosterone cypionate label says. We retrieved seven of them as XML on 20 September 2026 — Pharmacia & Upjohn’s Depo-Testosterone, Hospira, Cipla, Hikma, Sun, Eugia and Xiromed — and searched every one for “discard”, “punctur”, “beyond”, “in-use” and “28 day”. All five strings occur zero times in all seven. What every one of them does say is identical and is only about temperature: “Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Protect from light.” The 28 days people quote is real but is CDC’s, citing USP General Chapter <797>: “Once a multi-dose vial is opened (e.g., needle-punctured) the vial should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.” Date the vial at first puncture and follow it — just know it is a general rule about multi-dose vials, not something your vial says.
How many doses are in an Ozempic pen, and how long does it last?: Section 3 of the label states it rather than leaving it to arithmetic: “2 mg/3 mL (0.68 mg/mL) for 4 doses of 0.25 mg and 2 doses of 0.5 mg or 4 doses of 0.5 mg, 4 mg/3 mL (1.34 mg/mL) for 4 doses of 1 mg, and 8 mg/3 mL (2.68 mg/mL) for 4 doses of 2 mg”. Four weekly injections is 28 days. The pen’s in-use clock runs longer than that — “After first use of the OZEMPIC pen, the pen can be stored for 56 days” — so on a weekly schedule the drug always runs out first and the 56 days never binds. The Instructions for Use are blunt about which way the rule points if it ever did: “The OZEMPIC pen you are using should be disposed of (thrown away) after 56 days, even if it still has OZEMPIC left in it.”
Is a Wegovy pen four doses?: That depends entirely on which Wegovy you were dispensed, and the two are different products in the same carton design. The standard presentation is a SINGLE-dose pen — the carton reads “4 Single-Dose Prefilled Pens. Each pen delivers a single dose of 0.25 mg semaglutide”, so it is the CARTON that is four weeks, not the pen, and the label says “Discard the WEGOVY pen or syringe after use.” There is also a WEGOVY FlexTouch single-patient-use pen, “9.6 mg/3 mL (3.2 mg/mL) solution in a single-patient-use pen (WEGOVY FlexTouch) that delivers four 2.4 mg/0.75 mL doses”, and that one genuinely is four doses in one device, with a 56-day clock after first use. If you are counting what is left, check which of the two you are holding first.
How long does a Zepbound vial last after you open it?: ZEPBOUND is the one label on this page that states three ceilings in a single sentence and tells you to take whichever arrives first: “Throw away opened multi-dose vial or single-patient-use KwikPen after a total of 30 days at room temperature, 30 days after first use, or after taking 4 weekly doses, even if there is medicine left in it.” Four weekly doses is 28 days, so on a weekly schedule the dose count runs out two days before the 30-day clock and the drug runs out at the same moment — the 2.4 mL vial is built to hold exactly four. The single-dose pen and single-dose vial are a different question with a different answer: one dose, and a 21-day allowance out of the refrigerator before use, not after it.
How long does a reconstituted peptide vial last?: For an unapproved peptide, nobody has established that and we will not print a figure. A beyond-use date comes from stability testing of one formulation in one container, and no such data has been published for BPC-157, ipamorelin, retatrutide or the rest — so a number quoted to you has been borrowed from a different drug. For licensed peptides the figure exists and it is short and specific, which is the point: EGRIFTA WR is “Discard unused solution of EGRIFTA WR vial 7 days after mixing”, SEROSTIM 4 mg in bacteriostatic water “may be refrigerated at 2°C to 8°C (36°F to 46°F) for up to 14 days”, NOVAREL “should be refrigerated and used within 30 days” and PREGNYL is “STABLE FOR 60 DAYS WHEN REFRIGERATED”. Seven days to sixty, all FDA labels. There is no default to fall back on.
Does bacteriostatic water make the vial last 28 days?: No, and the 28 days does not come from the water. All seven standalone Bacteriostatic Water for Injection, USP labels on DailyMed were searched, and none states a post-puncture period, a discard date or a beyond-use date — the strings “28”, “day”, “punctur”, “discard” and “expir” occur zero times. What the water label does is hand the question to the drug: “Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.” The preservative is what allows a vial to be entered more than once; it is not a shelf life, and CDC is direct that it “does not have an effect on viruses nor does it provide complete protection against bacterial contamination.” The 28 days is CDC’s general multi-dose-vial rule, citing USP <797>.
Why does my pen still have medicine in it when the label says to throw it away?: Because the two ceilings rarely land on the same day, and the label is written to the shorter one. A SAXENDA pen at 3 mg daily holds 6 doses — 6 days — inside a 30-day window, so it empties long before the clock. Run the same pen at a smaller daily dose and it inverts: the drug would give more days than the pen is allowed, and the remainder is discarded. EGRIFTA WR is the extreme case on this page — the reconstituted vial deliverably holds 8 daily doses but the label allows 7, so 1.44 mg is thrown away by instruction. Only one configuration here wastes nothing: a SAXENDA pen at 0.6 mg, where 30 doses and a 30-day clock expire together.
My testosterone vial holds 20 weeks of drug but CDC says 28 days — which is it?: Both figures are right and they are answers to different questions, which is exactly why this is the most-asked version of it. 2,000 mg at 100 mg a week is 20 injections and 140 days of DRUG — that is arithmetic and it is not in dispute. CDC’s 28 days is a general infection-control rule for any punctured multi-dose vial, stated with an explicit escape clause: discard “within 28 days unless the manufacturer states another date for that opened vial”. Here no manufacturer states another date — we searched seven approved testosterone cypionate labels and found no post-puncture language of any kind — so the escape clause never opens and the general rule is all there is. This page will not adjudicate that for you, because no FDA label does. What it will do is show you both numbers instead of quietly printing whichever one you were hoping for. Your prescriber and your pharmacy are the people who can tell you which applies to the vial you were dispensed.
How many testosterone vials do I need for a year?: 3 vials at 100 mg once a week, if you buy the 10 mL 200 mg/mL presentation: each vial is 140 days, and 365 days divided by 140 rounds up to 3. On the 100 mg/mL vial the same prescription takes 6. Round up rather than down — running out mid-course is the expensive error, and the leftover is a spare vial. This is a count of containers, not a cost: /tools/trt-cost-calculator puts a sourced acquisition price against the same arithmetic.

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Compare TRT providersWho ships vials rather than a clinic visit, what presentation they send, and how many months arrive in a shipment.Compare GLP-1 providersBranded pens against compounded vials — including which ones tell you the beyond-use date before you buy.

Related calculators

Educational reference, not medical advice. This counts what is in a container at a dose and interval you enter. It does not tell you what dose to take, how often to take it, or whether a container is still safe to use. No dose on this page is a recommendation and none is sourced from a trial. Where a label states an in-use period, follow the label; where it states none, CDC’s rule for multi-dose vials is to date the vial at first puncture and discard within 28 days, never past the printed expiry. A compounding pharmacy’s beyond-use date overrides every figure here. Sterility is a matter of technique as much as time: a preservative limits bacterial growth, it does not protect against what a used needle introduces.