𧬠Peptide Dosage Calculator
From vial milligrams to syringe units, step by step.
For informational purposes only, not medical advice. Consult a healthcare professional.
Peptide dosing confuses people because three different units collide: the vial is labeled in milligrams, the dose is discussed in micrograms, and the syringe is marked in units. The conversion chain is straightforward once laid out. Divide the vial milligrams by the water milliliters to get concentration, convert the dose to the same units, and divide dose by concentration to get the injection volume. This calculator runs that chain and shows insulin-syringe units, since most peptides are measured with U-100 syringes. It is informational only: peptide use should be discussed with a clinician, and dosing decisions belong with one.
How to Use This Calculator
Enter the vial size in milligrams, how much bacteriostatic water you will add in milliliters, and the target dose in micrograms. The calculator converts to concentration, injection volume, and insulin-syringe units.
Enter the vial size from the label in mg and the water volume you plan to add in mL. More water means a more dilute solution and easier small-dose measurement.
Enter the desired dose in micrograms. Note the unit change: vials are labeled in mg, doses in mcg, and 1 mg equals 1,000 mcg.
Read the syringe units to draw. On a standard U-100 insulin syringe, 1 unit equals 0.01 mL, so the calculator converts volume to units directly.
How the Math Works
Convert the vial to micrograms by multiplying mg by 1,000, then divide by the water volume in mL to get concentration in mcg per mL. A 5 mg vial with 2 mL of water gives 5,000 mcg divided by 2, which is 2,500 mcg per mL. Divide the desired dose by the concentration to get the injection volume: 250 mcg divided by 2,500 mcg per mL is 0.1 mL. On a U-100 insulin syringe, multiply mL by 100 to get units: 0.1 mL is 10 units. Doses per vial are the vial total in mcg divided by the dose: 5,000 divided by 250 is 20 doses.
Worked Example
A 5 mg vial reconstituted with 2 mL of bacteriostatic water holds 5,000 mcg at 2,500 mcg per mL. A 250 mcg dose therefore needs 0.100 mL of solution, which reads as 10.0 units (U-100) on a U-100 insulin syringe. The vial yields 20.0 such doses. Adding 3 mL of water instead would dilute to about 1,667 mcg per mL and make the same dose 15 units, which some people find easier to measure accurately.
Reading Your Result
The units number is the practical output: draw to that mark on the syringe. If the units come out awkwardly small, like 2 or 3, consider reconstituting with more water so the dose lands on an easily readable mark; accuracy matters more than vial economy. If the dose exceeds the syringe capacity, split it or reconsider the plan with your clinician. Always double-check the mg-to-mcg conversion, because a factor-of-1,000 error is the classic and dangerous mistake in this arithmetic.
| Step | Example (5 mg, 2 mL, 250 mcg) |
|---|---|
| Vial in mcg | 5,000 mcg |
| Concentration | 2,500 mcg/mL |
| Injection volume | 0.1 mL |
| Syringe units | 10 units |
| Doses per vial | 20 |
Limitations
This calculator does arithmetic; it does not validate that a peptide, dose, or source is safe, legal, or appropriate. Many peptides sold online are unregulated with uncertain purity and content. Reconstitution requires sterile technique, and multi-dose vials carry contamination risk if handled poorly. Discuss any peptide use with a clinician or pharmacist before proceeding.
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For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
How do I convert mg to mcg for peptides?
Multiply milligrams by 1,000. A 5 mg vial contains 5,000 mcg. This single conversion is where most dosing errors happen, so write it out every time: mg times 1,000 equals mcg. Going the other way, divide mcg by 1,000 to get mg.
What are units on an insulin syringe?
On a U-100 insulin syringe, 100 units equals 1 mL, so 1 unit is 0.01 mL. A 0.1 mL injection reads as 10 units. The units scale is just a magnified milliliter scale designed for small, precise volumes. Always confirm your syringe is U-100 before using unit math.
How much bacteriostatic water should I add?
Enough to make the dose measurable accurately. Common choices are 1 to 3 mL for a 5 mg vial. More water dilutes the solution, so each dose becomes a larger, easier-to-read volume. There is no single correct volume; it is a trade-off between vial economy and measurement precision.
How long does a reconstituted vial last?
Kept refrigerated, most reconstituted peptides are used within 2 to 4 weeks, though stability varies by peptide and this is product-specific. Discard if the solution looks cloudy or discolored, and never use a vial past the date your pharmacist or clinician advises.
Can I mix two peptides in one syringe?
Sometimes done in practice, but compatibility, dosing accuracy, and contamination risk all need professional input. Do not assume it is fine because both are peptides. Ask the prescribing clinician or pharmacist about the specific combination.
What is the difference between bacteriostatic water and sterile water?
Bacteriostatic water contains a small amount of benzyl alcohol that inhibits bacterial growth, making it suitable for multi-dose vials used over days or weeks. Plain sterile water lacks the preservative and suits single use. For multi-dose peptide vials, bacteriostatic water is the standard choice.
Why do doses use mcg while vials use mg?
Convention and precision. Peptide doses are small enough that micrograms avoid constant decimals: 250 mcg reads cleaner than 0.25 mg. Vials are labeled in mg because that is the manufactured quantity. The calculator bridges the two automatically.
What if my dose needs more than the syringe holds?
Standard insulin syringes hold 30, 50, or 100 units (0.3, 0.5, 1 mL). If the calculated units exceed your syringe, split the dose into two injections or discuss a more concentrated reconstitution with your clinician. Never guess a partial syringe.
Are online peptides safe?
Many are sold as research chemicals without quality oversight, and independent testing has repeatedly found mislabeled content and contamination. A calculator cannot fix an unreliable product. Source and purity questions belong with a clinician and a licensed pharmacy.
Do I need to prime or account for dead space?
Insulin syringes have minimal dead space by design, so no correction is needed for typical peptide volumes. The larger errors come from unit misreading and mg-mcg confusion, which deserve the attention instead.