What is a tuberculin syringe?
A tuberculin syringe is a 1 mL syringe graduated in millilitres, with lines every 0.01 mL; BD lists its tuberculin syringe with a 1 mL capacity and a 0.01 mL scale.[1] An insulin syringe looks similar but is graduated in units for one insulin strength.[3]
Tuberculin syringe vs insulin syringe: same barrel, different scale
BD's 1 mL tuberculin syringe is listed with a capacity of 1 mL and a scale of 0.01 mL.[1] BD also makes 1 mL syringes with 0.01 mL, U-40 or U-100 graduations: the same barrel size, three different scales.[2] An insulin syringe's scale is designed for one insulin strength, U-100 or U-40.[3]
| Tuberculin syringe | U-100 insulin syringe | |
|---|---|---|
| Scale printed in | mL | Units of U-100 insulin |
| Smallest line (BD 1 mL) | 0.01 mL | 1 or 2 units, by model |
| 1 mL reads as | 1 (mL) | 100 (units) |
| 0.1 mL reads as | 0.1 | 10 |
Conversion chart
On a U-100 scale 100 units are 1 mL, so 0.01 mL is one unit.[4]
| Tuberculin (mL) | U-100 insulin syringe (units) | U-40 insulin syringe (units) |
|---|---|---|
| 0.01 mL | 1 | 0.4 |
| 0.05 mL | 5 | 2 |
| 0.1 mL | 10 | 4 |
| 0.2 mL | 20 | 8 |
| 0.25 mL | 25 | 10 |
| 0.5 mL | 50 | 20 |
| 0.75 mL | 75 | 30 |
| 1 mL | 100 | 40 |
Why insulin is measured with an insulin syringe
The printed numbers are where mix-ups start: a dose of 10 units is “0.1” on one syringe and “10” on the other. In 2024 the Institute for Safe Medication Practices reported a close call in which the packaging of a 1 mL U-100 insulin syringe and a 1 mL syringe with mL markings looked nearly identical.[5] ISMP has also reported that measuring concentrated insulin with tuberculin or U-100 syringes frequently led to miscommunication and wrong doses.[6] The U-500 insulin label names tuberculin and allergy syringes among those that can give the wrong dose.[7]
Use the syringe that matchesMeasure insulin with an insulin syringe whose scale matches the insulin strength, unless your prescriber tells you otherwise. Use the converter below to understand a volume, not to swap syringes.
Instructions that say “cc” mean mL; see cc to units. The full chart of mL against U-100, U-40 and U-500 units is on 1 mL = how many units, and the dedicated syringe that replaced tuberculin syringes for U-500 insulin is described in U-500 insulin syringe. For the three insulin syringe barrels, see insulin syringe sizes.
mL ⇄ units converter
U-100 · U-40 · U-500 · ccVolume
0.1 mL
= 0.1 cc
- U-100 scale
- 10 units
- U-40 scale
- 4 units
- U-500 insulin
- 50 units
- Smallest U-100 syringe
- 0.3 mL (30 units)
Formula: units = mL × scale (100, 40 or 500 units per mL). 1 mL = 1 cc.
Frequently asked questions
Is a tuberculin syringe the same as an insulin syringe?
Both can hold 1 mL, but a tuberculin syringe is marked in mL and an insulin syringe in units for a specific insulin strength.
How many units is 0.1 mL on a tuberculin syringe?
0.1 mL is the same volume as 10 units on a U-100 insulin syringe, or 4 units on a U-40 syringe.
Can I use a tuberculin syringe for insulin?
Labels and safety groups say to use an insulin syringe that matches the insulin strength. Ask your prescriber or pharmacist before using any other syringe.
Sources
- BD SafetyGlide tuberculin syringe, 1 mL (product 305945)
- BD Plastipak 3-piece syringe product family
- Technical data sheet: insulin syringes (Micro-Fine, Ultra-Fine)
- Giving an insulin injection
- Medication Safety Alert! Acute Care: insulin dosing error close call due to look-alike syringe packaging
- ISMP Guidelines for Optimizing Safe Subcutaneous Insulin Use in Adults
- Humulin R U-500 (insulin human) prescribing information and instructions for use