How to work out how long a vial lasts
A vial's total drug is its volume times its concentration. Divide that by your weekly dose to get weeks of supply; divide the vial's cost by those weeks to get cost per week.
- Enter the vial volume in mL from the label (e.g. 10 mL).
- Enter the concentration in mg/mL (e.g. 200 mg/mL).
- Enter your weekly dose as your provider prescribed it.
- Add the vial cost (optional) to see cost per week alongside weeks of supply.
Worked example: a 10 mL, 200 mg/mL vial at 100 mg/week
A 10 mL vial at 200 mg/mL, used at 100 mg a week, costing $80:
- Total in the vial — 10 mL × 200 mg/mL = 2,000 mg.
- Weeks of supply — 2,000 mg ÷ 100 mg/week = 20 weeks.
- Cost per week — $80 ÷ 20 weeks = $4.00/week.
A little is lost to syringe dead space in practice, so real-world weeks run slightly lower — enter your own vial and dose above.
Frequently asked questions
How long does a testosterone vial last?
Multiply the vial volume by its concentration to get the total drug, then divide by your weekly dose. A 10 mL vial at 200 mg/mL is 2,000 mg, so at 100 mg a week it lasts about 20 weeks. Enter your own numbers and the tool shows the steps.
What is syringe dead space and does it matter?
Dead space is the small volume left in the syringe and needle hub after injecting. Over many draws it slightly reduces the usable doses, so real-world supply runs a bit shorter than the ideal figure. The calculator can account for it if you add it.
How do I work out cost per week?
Divide the vial’s cost by its weeks of supply. If a vial lasts 20 weeks and costs $80, that is $4.00 per week. It is a simple way to compare products or plan a budget.
Is this vial calculator medical advice?
No. It is an educational estimation tool that does the arithmetic and shows its work; it never recommends a dose. Always follow your licensed provider’s instructions.
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