U-40 vs U-100: why are the syringe scales different?
U-40 and U-100 specify concentration, not barrel volume. U-40 is calibrated for 40 units per mL. U-100 is calibrated for 100 units per mL. Both scales are offered in 0.5 mL and 1 mL barrels.
Key specifications compared
| Specification | U-40 | U-100 | Source |
|---|---|---|---|
| Scale calibration | 40 units/mL | 100 units/mL | UltiMed |
| Needle-cap colour | Red | Orange | MSF; UltiMed |
| Published unit-capacity examples | 1/2 cc: up to 20 units; 1 cc: up to 40 units | 3/10 cc: up to 30 units; 1/2 cc: up to 50 units | Banfield |
| CarePoint Vet, 3/10 cc, 29G × 1/2" | Item 12-4903; UPC 786227490359 | Item 12-7903; UPC 786227790350 | Allison Medical |
| CarePoint Vet, 1/2 cc, 29G × 1/2" | Item 12-4905; UPC 786227490557 | Item 12-7905; UPC 786227790558 | Allison Medical |
| CarePoint Vet, 1 cc, 29G × 1/2" | Item 12-4910; UPC 786227491059 | Item 12-7910; UPC 786227791050 | Allison Medical |
| UltiMed U-100 gauge/length pairs | — | 31G × 6 mm; 31G × 8 mm; 30G × 8 mm; 30G × 12.7 mm; 29G × 12.7 mm; 28G × 12.7 mm | UltiMed |
Why the scales differ
A piston syringe uses a calibrated hollow barrel and a movable plunger. FDA lists insulin syringes under product code FMF, regulation 21 CFR 880.5860. The FDA classification record does not create separate device types for U-40 and U-100; the distinguishing property is the barrel calibration.
As reproduced in Médecins Sans Frontières’ procurement specification for ISO 8537, an insulin syringe indicates the concentration it is intended to contain, and its scale is graduated in units of only one concentration. The barrel is also marked with that concentration. U-40 and U-100 are therefore different printed calibrations, even where the nominal barrel capacity and needle dimensions match.
Wenzhou Wuzhou’s FDA 510(k) summary lists 0.5 mL and 1 mL syringes in both concentrations. Allison Medical shows the same product pattern in matched rows: a 1 cc, 29G × 1/2" barrel appears as item 12-4910 on the U-40 scale and item 12-7910 on the U-100 scale, with different UPCs. Their 3/10 cc and 1/2 cc syringes also share the 29G × 1/2" needle dimensions.
UltiMed lists its U-40 syringes under animal health and its U-100 syringes under consumer health, and prints “FOR ANIMAL USE ONLY” on the U-40 line. That is why the U-40 references here are veterinary catalogues.
Nominal capacity and unit scale are separate fields. A capacity label does not identify the concentration scale. The product record also matters: Allison Medical item numbers distinguish near-identical variants, while UltiMed publishes gauge and needle length as fixed pairs. Its U-100 grid lists no 31G × 12.7 mm or 28G × 6 mm combination.
UltiMed lists its 1.0 mL U-100 syringe at 2-unit increments, while MSF lists 1 IU or 2 IU. U-40 listings state whole-unit markings and identify half-unit options. Red and orange cap colours correspond to U-40 and U-100 respectively. The printed concentration remains the explicit barrel identifier.
Where to buy
Both scales sell at ordinary retail in 100-count boxes. U-40 is stocked as a veterinary product.
- UltiCare VetRx U-40 3/10cc Pet Insulin Syringes — 29G x 1/2", half-unit markings, 100 ct
- UltiCare U-100 Insulin Syringes — 1cc, 29G x 12.7mm, 100 count
Sources
- eCFR — 21 CFR 880.5860, Piston syringe
- FDA — Product Classification database, product code FMF
- Médecins Sans Frontières — UniCat insulin syringe specification
- FDA 510(k) K110421 — Wenzhou Wuzhou Import & Export Co., Ltd., Disposable Insulin Syringe
- Allison Medical, Inc. — CarePoint Vet U-40 and U-100 data sheet
- UltiMed, Inc. — UltiCare U-100 Insulin Syringes
- UltiMed, Inc. — UltiCare VetRx U-40 Insulin Syringes
- Banfield Pet Hospital — UltiCare VetRx U-40 Insulin Syringes
- Banfield Pet Hospital — UltiCare VetRx U-100 Insulin Syringes
Specifications last verified: 2026-07-31