Units vs. milliliters
Insulin syringes are marked in units, not milliliters. Understanding the relationship between these measurements is essential for drawing your prescribed dose accurately.
The key conversion
100 units = 1 mL
This is true for all standard insulin syringes. So 10 units = 0.10 mL, 50 units = 0.50 mL, and so on. When your dosing card says "draw 20 units," that's 0.20 mL of solution.
1 mL Syringe
100 units total. Lines every 2 units. Most common for peptide dosing. Good for doses from 2 to 100 units.
0.5 mL Syringe
50 units total. Lines every 1 unit. Better precision for small doses. Good for doses under 50 units.
0.3 mL Syringe
30 units total. Lines every 1 unit. Best precision for very small doses. Used for doses under 30 units.
How to read syringe markings
On a 1 mL (100-unit) insulin syringe - the most common type included in your kit.
Understanding the lines on a 100-unit syringe
- Long lines with numbers (10, 20, 30... 100) = major markings in 10-unit increments
- Medium lines between numbered lines = 5-unit marks (halfway between major lines)
- Short lines between medium lines = 2-unit marks (each small tick = 2 units)
- The black rubber stopper inside the syringe = the indicator. Read where the flat edge (top edge, closest to the needle) meets the markings
Quick reference: common dose markings
| Units to Draw | mL Equivalent | Where on Syringe |
|---|---|---|
| 5 units | 0.05 mL | Halfway between 0 and the first short line |
| 10 units | 0.10 mL | First numbered line (10) |
| 15 units | 0.15 mL | Halfway between 10 and 20 |
| 20 units | 0.20 mL | Second numbered line (20) |
| 25 units | 0.25 mL | Halfway between 20 and 30 |
| 50 units | 0.50 mL | Halfway point of syringe (50) |
Step-by-step: loading the syringe
How to accurately draw your dose from a reconstituted vial.
Sterilize the vial top
Wipe the rubber stopper with a fresh alcohol swab. Let it air dry completely. Do this every single time you draw from the vial, even if you just used it.
Pull back the plunger to your dose
Before inserting the needle into the vial, pull the plunger back to the marking that matches your prescribed dose. This fills the syringe with air equal to the volume you'll draw. This step prevents a vacuum inside the vial.
Inject air into the vial
Push the needle through the center of the rubber stopper. With the vial upright on your workspace, push the plunger down to inject the air into the vial. This equalizes pressure and makes drawing the liquid easier.
Invert the vial and draw
Flip the vial upside down with the syringe still inserted. Make sure the needle tip is submerged in the liquid. Slowly pull the plunger down past your target dose by a few units - you'll adjust in the next step.
Remove air bubbles
With the vial still inverted, flick the syringe barrel gently with your finger to move air bubbles to the top (near the needle). Slowly push the plunger up until the top of the rubber stopper aligns exactly with your prescribed dose marking. A tiny drop of liquid at the needle tip means all air is out.
Remove and double-check
Pull the needle out of the vial. Hold the syringe at eye level with the needle pointing up. Verify the top edge of the rubber stopper is at your prescribed dose line. You're ready to inject.
How to calculate units from your concentration
If you know your concentration (mg/mL) and prescribed dose (mg), use this formula to calculate how many units to draw.
Units = (Dose ÷ Concentration) × 100
Example: Your vial is 5 mg reconstituted in 2 mL = 2.5 mg/mL concentration.
Your prescribed dose is 0.5 mg.
(0.5 ÷ 2.5) × 100 = 20 units
More examples
- 0.25 mg dose at 2.5 mg/mL: (0.25 / 2.5) × 100 = 10 units
- 0.5 mg dose at 5.0 mg/mL: (0.5 / 5.0) × 100 = 10 units
- 1.0 mg dose at 2.5 mg/mL: (1.0 / 2.5) × 100 = 40 units
- 1.0 mg dose at 5.0 mg/mL: (1.0 / 5.0) × 100 = 20 units
- 2.5 mg dose at 5.0 mg/mL: (2.5 / 5.0) × 100 = 50 units
Always double-check your calculation against your dosing card. If your numbers don't match, contact your care team before injecting. Use the interactive dose calculator on our injection instructions page.
Syringe FAQ
Related guides
Questions about your medication?
Your care team can walk you through dosing calculations and syringe technique.