The visual guide to precise administration. Toggle between standard 1mL and U-100 syringes to see exactly where the liquid level should land for your calculated dose.
For a dose, pull the plunger back until the top ring of the black stopper aligns with the corresponding mark.
Pro Tip: When drawing medication, tap the syringe to remove air bubbles. Even a small bubble can displace 0.05mL of dose, leading to a 5-10% error in small doses.
A standard 1mL syringe (often called a tuberculin syringe) is marked with lines every 0.01mL. The large numbers represent 0.1mL increments. When a doctor prescribes 0.45mL, you count four major lines (0.4) and then five small tick marks.
Measurement should be read from the top ring of the plunger—the part closest to the needle—not the bottom of the black rubber or the point of the dome.
Insulin syringes are calibrated in "Units" rather than milliliters. For a U-100 syringe, 100 units is exactly 1.0mL. This means 1 Unit = 0.01mL. Mixing up U-100 and U-40 syringes can lead to a 2.5x overdose or underdose, which is why visual verification is critical.
Dead space is the tiny amount of fluid left in the needle and hub after the plunger is fully depressed. Most syringes are "To Deliver" (TD) calibrated, meaning they account for this.
Most 1mL syringes only have 0.01mL resolution. Round to the nearest mark (0.46mL) unless your clinician specifies otherwise.
Higher Gauge Number = Thinner Needle
| Gauge (G) | Common Color | Best Use Case | Viscosity Limit |
|---|---|---|---|
| 31G | Purple | Insulin, Peptides (SubQ) | Water-like |
| 27G | Grey | Vaccines, Hormones | Thin Oils |
| 23G - 25G | Blue | Intramuscular (IM) | Thick Oils |
| 18G - 21G | Pink | Drawing Up Only | Any |
Dr. Igor I. Bussel is a board-certified ophthalmologist and fellowship-trained surgeon affiliated with the University of California, Irvine (UCI), the Gavin Herbert Eye Institute, and the UCI School of Medicine.
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