Contents
On a 100-unit (U-100) insulin syringe, 1 unit = 0.01ml. To find your units: divide your dose (mcg) by your concentration (mcg/ml), then multiply by 100. Example: 250mcg dose ÷ 2,500 mcg/ml × 100 = 10 units.
Insulin syringes are the standard tool for peptide injection — they’re thin, precise, and widely available. But if you’ve never used one before, the markings can be confusing. This guide explains exactly what every line and number means, and how to draw the right volume for any peptide dose.
Use the Peptide Reconstitution Calculator to get the exact unit reading for your dose before you draw anything.
What Type of Syringe Do You Need?
For peptide injections, you need a U-100 insulin syringe — also called a 100-unit syringe. This is the standard insulin syringe available at pharmacies without a prescription in most countries.
Key specs:
- Total capacity: 1ml (= 100 units)
- Graduation: Each small line = 1 unit (= 0.01ml)
- Needle gauge: 27–31 gauge (thinner = less painful)
- Needle length: 4–8mm (0.16”–0.31”) for subcutaneous injection
Half-unit (0.5ml, 50-unit) syringes are also available and can be useful for smaller doses, but 1ml syringes are more common and work for the full range of peptide doses.
Understanding the Markings
A standard U-100 insulin syringe has markings from 0 at the tip to 100 at the plunger end (or 0 to 1.00ml on some syringe types).
The numbered markings (10, 20, 30, 40, 50, 60, 70, 80, 90, 100) indicate units. Each represents 10 units, which equals 0.10ml.
The small lines between numbers each represent 1 unit (0.01ml). There are 9 small lines between each numbered mark, plus the numbered mark itself, giving you 10 increments between each major mark.
| Marking | Units | Volume |
|---|---|---|
| 10 | 10 units | 0.10 ml |
| 20 | 20 units | 0.20 ml |
| 25 | 25 units | 0.25 ml |
| 30 | 30 units | 0.30 ml |
| 40 | 40 units | 0.40 ml |
| 50 | 50 units | 0.50 ml |
| 100 | 100 units | 1.00 ml |
What Are Units?
“Units” on an insulin syringe were originally designed for insulin dosing — insulin is prescribed in international units (IU), not ml. But for peptide dosing, we use the syringe markings as a convenient proxy for volume.
For peptides, 1 unit = 0.01ml. That’s all you need to know.
When a peptide calculator tells you your dose is “10 units,” it means draw the plunger back to the 10-unit line, which equals 0.10ml of solution.
The term “units” for peptides has nothing to do with biological activity or international units (IU). It’s purely a volume measurement tied to the syringe markings.
How to Convert ml to Units
To convert from milliliters (ml) to units on a U-100 syringe:
Units = ml × 100
| ml | Units |
|---|---|
| 0.05 ml | 5 units |
| 0.10 ml | 10 units |
| 0.15 ml | 15 units |
| 0.20 ml | 20 units |
| 0.25 ml | 25 units |
| 0.30 ml | 30 units |
| 0.40 ml | 40 units |
| 0.50 ml | 50 units |
To convert units back to ml: ml = units ÷ 100
How to Calculate Your Units From Dose
The full calculation, starting from your peptide dose:
- Know your concentration (mcg/ml) — from your reconstitution
- Know your dose (mcg) — from your protocol
- Injection volume (ml) = dose (mcg) ÷ concentration (mcg/ml)
- Units = injection volume (ml) × 100
Example — BPC-157:
- Vial: 5mg, BAC water: 2ml → Concentration: 2,500 mcg/ml
- Dose: 250mcg
- Volume: 250 ÷ 2,500 = 0.10ml
- Units: 0.10 × 100 = 10 units → draw to the 10-unit line
Example — Semaglutide:
- Vial: 10mg, BAC water: 2ml → Concentration: 5,000 mcg/ml
- Dose: 500mcg
- Volume: 500 ÷ 5,000 = 0.10ml
- Units: 0.10 × 100 = 10 units → draw to the 10-unit line
Example — TB-500:
- Vial: 5mg, BAC water: 2ml → Concentration: 2,500 mcg/ml
- Dose: 2,000mcg
- Volume: 2,000 ÷ 2,500 = 0.80ml
- Units: 0.80 × 100 = 80 units → draw to the 80-unit line
Use the Peptide Reconstitution Calculator to do this automatically for any vial and dose combination.
Peptide Dose Reference Table — Common Unit Readings
At the standard 2,500 mcg/ml concentration (5mg vial + 2ml BAC water):
| Dose | Units | ml |
|---|---|---|
| 100 mcg | 4 units | 0.04 ml |
| 200 mcg | 8 units | 0.08 ml |
| 250 mcg | 10 units | 0.10 ml |
| 300 mcg | 12 units | 0.12 ml |
| 400 mcg | 16 units | 0.16 ml |
| 500 mcg | 20 units | 0.20 ml |
| 750 mcg | 30 units | 0.30 ml |
| 1,000 mcg | 40 units | 0.40 ml |
At the standard 5,000 mcg/ml concentration (10mg vial + 2ml BAC water):
| Dose | Units | ml |
|---|---|---|
| 250 mcg | 5 units | 0.05 ml |
| 500 mcg | 10 units | 0.10 ml |
| 1,000 mcg | 20 units | 0.20 ml |
| 2,500 mcg | 50 units | 0.50 ml |
| 5,000 mcg | 100 units | 1.00 ml |
Step-by-Step: How to Draw the Correct Amount
Step 1: Calculate your units
Use the calculator above or the formula to find your target unit number before touching the syringe.
Step 2: Pull air into the syringe
Draw back the plunger to your target unit mark before inserting the needle into the vial. This creates air pressure that helps draw the solution out cleanly.
Step 3: Insert the needle into the vial
Pierce the rubber stopper with the needle at a slight angle. Push the air in, then invert the vial.
Step 4: Draw to your unit mark
Pull the plunger back until the bottom of the plunger head aligns with your target unit line. The bottom edge of the plunger is the measurement edge — not the top.
Step 5: Check for air bubbles
Tap the syringe gently and push small bubbles to the top. Push the plunger slightly to expel bubbles, then draw back to your target unit if needed.
Step 6: Remove the needle from the vial
Withdraw the syringe and check the volume once more before injecting.
Common Mistakes When Reading Insulin Syringes
1. Reading from the wrong edge of the plunger
The measurement is taken from the bottom edge of the rubber plunger, not the top. If your plunger has a raised dome shape, the lower flat edge is the measurement edge.
2. Miscounting small lines
Between major markings (e.g., 10 to 20), there are 9 small lines plus the line at 20, making 10 total increments. Counting carefully is important — especially for small doses like 5 or 7 units.
3. Drawing too fast
Pulling the plunger back quickly can create turbulence and air bubbles, making it harder to get an accurate reading. Draw slowly.
4. Measuring after removing from the vial
Always check your unit reading while the needle is still in the vial. Once you remove it, any adjustment requires re-inserting, increasing contamination risk.
5. Using a unit-10 syringe for peptides
Some insulin syringes are calibrated for U-40 insulin (40 units/ml), not U-100 (100 units/ml). A U-40 syringe has different markings and cannot be used interchangeably with U-100 dosing calculations. Always confirm you have a U-100 (100-unit) syringe.
Choosing the Right Syringe Size
1ml (100-unit) syringe: Works for doses from 5 units (0.05ml) to 100 units (1ml). Suitable for most peptide protocols.
0.5ml (50-unit) syringe: Better resolution for small doses below 25 units — each small line still represents 1 unit, but the scale is larger and easier to read precisely.
0.3ml (30-unit) syringe: Best for very small doses (under 15 units). The magnified scale makes precise measurement easier for low-dose protocols.
For most peptide users, a 1ml U-100 syringe works for the full range of common doses. If your dose is consistently below 20 units, a 0.5ml syringe gives a larger, easier-to-read scale.
Needle Gauge and Length
Gauge describes the needle’s thickness — higher gauge numbers = thinner needles. For peptide injections:
- 27 gauge: Standard, comfortable for most users
- 29–31 gauge: Thinner, less resistance, minimal pain — preferred for daily injections
Length determines injection depth:
- 4mm (5/32”): For subcutaneous injection in lean individuals
- 6mm (1/4”): Standard subcutaneous, works for most body compositions
- 8mm (5/16”): Subcutaneous in areas with more fat, or for IM injection
For subcutaneous peptide injections (the most common route), 29–31 gauge, 6–8mm needles are the standard recommendation. For a full guide on injection technique, see how to inject peptides.
FAQ
What does “10 units” mean for peptides? It means draw the plunger back to the 10-unit line on a U-100 insulin syringe. That equals 0.10ml of solution. The peptide content depends on your solution’s concentration.
Can I use a regular syringe instead of an insulin syringe? Standard medical syringes are graduated in ml (tenths or hundredths), not units. You can use them, but you need to calculate ml rather than units. Insulin syringes are preferred because they’re designed for precise, low-volume measurements.
Why do some peptide calculators show units instead of ml? Units are used because they directly correspond to syringe markings, making it easier to set up your injection without conversion. The underlying measurement is always ml — units are just a convenient shorthand for U-100 syringe users.
What if my dose calculation gives a non-whole number like 7.5 units? Draw to the closest line you can reasonably read. Most insulin syringes have 1-unit graduations, so 7 or 8 units is the practical range. For more precision, consider using a 0.5ml syringe where the lines are physically larger, or adjusting your BAC water volume to change concentration so your dose lands on a whole unit number.
My syringe markings go up to 100 but the numbers only show 10, 20, 30… Is something wrong? No — that’s standard. The numbers 10, 20, 30, etc. represent 10 units each. There are 9 small lines between each number, plus the number line itself, giving you 10 individual unit marks per major interval. Count each small mark as 1 unit.
For informational purposes only. Consult a healthcare professional before using any peptide compound.
This article is for informational and educational purposes only. It does not constitute medical advice. Always consult a qualified healthcare professional before using any peptide compound. Calculator results are mathematical estimates — verify all doses with a licensed clinician.