Vial supply calculator
A vial lasts its volume divided by the volume of each dose, times the days between doses, minus a little lost in the needle each time. Enter your vial, your prescribed dose and how often you inject to see how many doses it holds, the date it runs out and when to order a refill.
This is an educational estimate, not medical advice. It doesn’t recommend a dose. Real levels vary a lot between people; only a blood test shows yours. Talk to your prescriber before changing anything. Use the dose your prescriber set, and check your vial’s beyond-use date with your pharmacy.
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- Last dose from your supply
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- Order a refill by
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- Left in each vial
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- Lost to dead space per vial
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TRTracker tracks your vial and warns you before you run out.
Every injection you log comes off the vial, so the run-out date stays right. Free on iPhone.
How it works
If your dose is in mg, the calculator first turns it into mL with the strength on your vial (mL = mg ÷ mg/mL). Then:
doses per vial = vial mL ÷ (dose mL + dead space), rounded down
Only whole doses count: the oil that is left is not enough for another full injection. The run-out date is the first injection date your supply can no longer cover, counted from the first dose you take from this vial. With more than one vial the doses add up.
Dead space is the oil left in the needle hub and syringe tip each time. It is close to nothing with an insulin syringe and fixed needle, and more with a separate needle on a Luer-Lock syringe. If you are not sure, 0.05 mL is a cautious allowance.
The dates assume you inject on schedule and lose nothing to spills or a dropped dose.
Sources
Questions
How long will a 10 mL vial of testosterone last?
Divide the vial’s volume by the volume of each dose, then multiply by the days between doses. A 10 mL vial at 0.5 mL a week gives 20 doses, about 20 weeks. Allow a little for what stays in the needle and syringe each time.
What is dead space?
The liquid left in the needle hub and syringe tip after you inject. It is lost with every draw. Insulin syringes with a fixed needle waste almost nothing; a separate needle on a Luer-Lock syringe can hold several hundredths of a mL.
Can I use the last bit of a vial?
Usually a little oil remains that a needle cannot reach. Some vials are filled slightly over their label volume, but do not count on it. Never combine leftovers from different vials, and check the vial’s beyond-use date with your pharmacy.
When should I order a refill?
Early enough for your pharmacy and prescriber: the calculator sets a reminder 3, 7 or 14 days before the run-out date. Prior authorisations and mail delivery can take longer.
Is anything I type saved?
No. The dates are worked out in your browser and nothing is stored. The calendar file and the PDF are made on your device. If you ask us to email it, we send it once and keep no copy of it or your address.
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- Free testosterone calculatorEstimate free and bioavailable testosterone from total T, SHBG and albumin (Vermeulen).
- All toolsEvery free calculator, including the ones on the way.
Your real curve, in your pocket
Log each injection and lab result. TRTracker redraws the curve for you, with the uncertainty range.
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Free tools for education only. Nothing you type here is stored; the maths runs in your browser, and your result is only sent if you ask us to email it. TRTracker does not provide medical advice, diagnosis or treatment. Privacy policy