Insulin syringe sizes
To read your dose clearly, compare 0.3 mL, 1 mL and 0.5 mL U-100 insulin syringe sizes, along with barrel unit marks, needle gauges and lengths.
- Syringe size 0.3 mL
- 30 units
- Syringe size 0.5 mL
- 50 units
- Syringe size 1 mL
- 100 units
- U-100 syringe, per 1 unit
- 0.01 mL
You can choose standard U-100 insulin syringe sizes with 0.3 mL and 1 mL barrels, plus a 0.5 mL option, for 3 volume choices. Each 1 mL of liquid contains 100 units on a U-100 syringe. That makes the 3 barrels hold 30, 50, or 100 units. Your dose comes from your prescriber, and we show how barrel and needle sizes work so you can read each line clearly.
| Syringe | Holds | Marks every | Common gauges | Needle lengths |
|---|---|---|---|---|
| 0.3 mL (30 unit) U-100 | 0.3 mL = 30 units | 1 unit (some show half units) | 30, 31 | 5/16 in, 15/64 in |
| 0.5 mL (50 unit) U-100 | 0.5 mL = 50 units | 1 unit | 30, 31 | 5/16 in, 15/64 in |
| 1 mL (100 unit) U-100 | 1 mL = 100 units | 2 units | 29, 30, 31 | 5/16 in, 1/2 in |
| 1 mL (40 unit) U-40 | 1 mL = 40 units | 1 unit | 29 | 1/2 in |
30 unit insulin syringe and 0.3 mL insulin syringe sizes
Among the available U-100 syringes, the narrowest holds up to 30 units of liquid in a 0.3 mL barrel. The slim tube spreads the printed lines farther apart, and the added space makes it much easier to see small doses.
Marks on every 0.3 mL barrel appear at 1 unit intervals, and some barrels add 0.5 unit marks for finer measurements. Thin 30 or 31 gauge needles usually pair with this barrel, at 5/16 inch or 15/64 inch long. For a small draw, including 10 units in mL, our insulin syringe reading guide explains how to align the plunger tip cleanly.
0.5 mL barrel for a 50 unit insulin syringe
Up to 50 units of liquid fit in a 0.5 mL U-100 syringe; at full capacity, that amount equals 0.5 mL. This size works well as a middle choice when your draw is over 30 units, or when a 30 unit barrel feels too full.
From the tip to the 50 mark, the 0.5 mL syringe has a line every 1 unit, like the smaller 0.3 mL barrel. Every unit has a clear black tick, so odd-numbered doses can be measured without guessing between even numbers. Needles of 30 and 31 gauge are common on a 50 unit syringe, with lengths of 5/16 inch and 15/64 inch.
100 unit insulin syringe: the 1 mL syringe with 100 units
Liquid capacity for the full-size barrel reaches up to 100 units, and it is a 1 mL U-100 model. We use this size if one draw exceeds 50 units, or if you mix bacteriostatic water into a vial.
On a 100 unit barrel, watch the scale closely because each line is printed every 2 units, not every 1 unit. For an odd dose such as 15 units, stop the plunger midway between the 14 and 16 marks. Needles for these barrels are available at 29, 30 or 31 gauge, with lengths of 5/16 inch and 1/2 inch. You can convert any mark on the barrel with our units to mL reference.
Gauges 29, 30 and 31; lengths 5/16 and 1/2 inch
Gauge tells you how thick a needle is, and a higher gauge number means a thinner shaft. According to Healthline, thinner needles may be more comfortable on the skin. A needle at 31 gauge has a thinner shaft than one at 29 or 30 gauge.
Subcutaneous injections only have to put liquid into the fat layer right under the skin, not deep into muscle. A 5/16 inch or 15/64 inch needle helps you avoid hitting muscle, more so than a 1/2 inch needle. Our best syringes for peptides page compares these barrel and needle pairings in more detail.
Why aren't 40 unit U-40 syringes suitable for peptides?
A U-40 syringe is made for veterinary pet insulin, including UltiCare VetRx. Its barrel carries 40 units within 1 mL of liquid. This 1 mL pet syringe has marks spaced every 1 unit through 40, and it usually includes a 29 gauge, 1/2 inch needle.
Every standard peptide chart and calculator assumes a U-100 barrel, in which 100 units equal 1 mL. Don't use U-100 unit numbers to measure on a U-40 syringe, since every U-40 unit measures 2.5 times as much and gives the wrong dose.
Questions people often ask
Is a 0.25 mL insulin syringe available?
Our syringe list's smallest U-100 barrel is the 0.3 mL syringe. It holds 30 units, with marks at 1 unit or 0.5 unit intervals.
What does 1 unit mean on a syringe?
With a U-100 syringe, 1 unit measures 0.01 mL of liquid. So 10 units measure 0.1 mL, while 50 units measure 0.5 mL and 100 units measure 1 full mL.
What size of insulin syringe is right for me?
Your full unit dose should fit in 1 draw, so pick the smallest U-100 barrel that can hold it. Healthline says a 0.3 mL syringe handles doses under 30 units well; its wider line spacing helps you read small amounts.