Insulin Syringes — The Standard Tool

Nearly all peptide protocols use insulin syringes. They are designed for small, precise volumes, feature thin-gauge needles (29G, 30G, 31G), and have a pre-attached fixed needle that reduces dead space. They are labeled by capacity and unit scale, and understanding those labels is the first step to accurate dosing.

Syringe Types and Scales

U-100 (1 mL)

The most common syringe. 100 units = 1 mL. Each unit = 0.01 mL. Smallest graduation typically 2 units. Best for doses of 10–100 units.

U-100 (0.5 mL)

The half-milliliter version. Same unit scale as the 1 mL but only holds 50 units maximum. The markings are more spread out, making it easier to read small volumes. Smallest graduation typically 1 unit. Best for doses of 5–50 units.

U-100 (0.3 mL)

The smallest common insulin syringe. Holds 30 units. Features half-unit markings. Most precise option for tiny doses. Best for doses of 1–30 units.

U-50

Less common. 50 units = 0.5 mL. Each unit = 0.01 mL — the same volume-per-unit as U-100. Labels differ but the volume math is identical. Best for small precise doses.

U-20

Primarily veterinary. 20 units = 0.2 mL. Widest spacing between marks. Best for ultra-small doses.

How to Read a Syringe

1. Identify syringe type — check barrel print for “U-100”, “U-50”, or “U-20” and capacity (1 mL, 0.5 mL, 0.3 mL).
2. Understand the lines — numbered marks at every 10 units on 1 mL syringes, single-unit on 0.5 mL syringes, half-unit on 0.3 mL syringes.
3. Read at the plunger tip — align your eye with the top flat edge of the rubber stopper. Do not read at the bottom curve. Hold the syringe at eye level to avoid parallax error.
4. Account for air bubbles — hold the syringe needle-up, flick the barrel to dislodge bubbles, push them out, and re-draw if needed.

The Three Unit Systems

This is where most beginners get confused. Three distinct unit systems are in common use, and mixing them is the source of nearly all dosing errors.

Weight: mg and mcg

Measure peptide by mass. 1 mg = 1,000 mcg. Critical: confirm whether your protocol uses mg or mcg. A 1,000× dosing error results if these are confused. Always verify the abbreviation — “mg” and “mcg” are not interchangeable.

Volume: mL and syringe units

Measure liquid. 1 mL = 100 units on a U-100 syringe. 1 unit = 0.01 mL. Syringe “units” are purely volume markings — they do not indicate peptide dose until you know the concentration of your reconstituted solution.

Potency: IU (International Units)

Measure biological activity for specific peptides (primarily HGH at ~3 IU per 1 mg, and HCG). Not the same as syringe units. When a protocol says “inject 2 IU of HGH,” you must calculate the volume based on your reconstitution concentration.

Conversion Math

Three-step formula to go from a peptide dose to syringe units:

Quick-Reference Conversion Tables

mg to mcg

mL to U-100 syringe units

HGH IU to syringe units (10 IU vial + 1 mL BAC water)

Common Mistakes

• Confusing syringe units with IU. The most dangerous error. “Inject 2 IU of HGH” does not mean drawing to “2” on the syringe. Calculate volume from your reconstitution concentration first.
• Confusing mg and mcg. 250 mcg vs. 250 mg = a 1,000× dosing error. Always verify the abbreviation written in your protocol.
• Reading the wrong part of the plunger. Read the top flat edge of the rubber stopper, not the bottom curve or the needle hub.
• Not accounting for air bubbles. A 5-unit air bubble in a 15-unit draw means only 10 units of actual liquid is drawn.
• Using the wrong syringe for dose volume. 5 units on a 1 mL syringe is nearly impossible to read accurately. Switch to a 0.3 mL or 0.5 mL syringe.
• Assuming all syringes use the same scale. U-40 syringes exist in veterinary contexts with a different relationship between marks and volume. Always verify the syringe type.

Needle Gauge and Length

Gauge (thickness)

• 29G — Standard/slightly thicker needle
• 30G — Most popular; good balance of thinness and durability
• 31G — Thinnest; least discomfort but more fragile

Higher gauge number = thinner needle.

Length

• 1/2 inch (12.7 mm) — Most common for subcutaneous injections
• 5/16 inch (8 mm) — For leaner body types or shallow injection

Which Syringe Should I Use?

For reconstitution: Use a 1 mL syringe when adding 1–3 mL of BAC water to a vial.  For daily dosing: Use the smallest syringe that comfortably holds your calculated dose volume.

Measurement Checklist

1. Confirm protocol dose and unit (mg / mcg / IU)
2. Check your reconstitution concentration
3. Calculate dose volume in mL
4. Convert mL to syringe units
5. Select the appropriate syringe size for your dose volume
6. Verify the syringe is U-100
7. Draw and check for air bubbles
8. Read at the top flat edge of the plunger, at eye level
9. Confirm your reading before injecting