31G vs 30G insulin syringes: which needle?
Quick answer
31G is thinner than 30G. The gauge number runs backwards: higher means thinner. On a fixed-needle insulin syringe the 31G needle is about 0.26 mm (0.010 in) across and the 30G about 0.31 mm (0.012 in), a difference most people feel as "slightly less" rather than "painless". The bigger choice is usually the barrel that comes attached: 31G needles come on 0.3 and 0.5 mL syringes, 30G on the 1 mL.
Side by side
Rows that differ are highlighted. Values come from the product records for the two products named in the header.
31G Insulin Syringes 31G, 0.5 mL (100-count) |
30G Insulin Syringes 30G, 1 mL (100-count) |
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|---|---|---|
| GaugeGauge is the needle's thickness. A higher number is a thinner needle: 31G is thinner than 30G. Glossary | 31G | 30G |
| CapacityCapacity is how much liquid the barrel holds. Smaller barrels have more space between the lines, so small amounts are easier to read. Glossary | 0.5 mL | 1 mL |
| MarkingsMarkings are the scale printed on the barrel. U-100 means 100 units to the millilitre, so one unit is 0.01 mL; a mL scale is marked in tenths or fifths of a millilitre, depending on the barrel. Glossary | U-100 | U-100 |
| Smallest lineSmallest line is what one line on the barrel is worth. Half-unit lines let you read 0.005 mL; a 1 mL syringe is usually marked in 2-unit steps. Glossary | 1 unit | 2 units |
| Needle lengthNeedle length is how long the needle is. 4–8 mm (5/32–5/16 in) is common for under-the-skin use, and 13 mm (1/2 in) insulin syringes are used under the skin too; muscle needles are usually 25 mm (1 in) or longer. Glossary | 8 mm | 13 mm |
| Needle connectionNeedle connection is how the needle attaches. Fixed means it is built in (least dead space). Luer-lock screws on and cannot pop off. Luer-slip pushes on. None means there is no luer fitting at all — a pen needle screws onto the pen's own thread. Glossary | Fixed needle | Fixed needle |
| Needle included | Yes | Yes |
| TipTip is the shape of the needle's point. A blunt tip is far less likely to stick you while mixing and drawing up, but it is still a sharp that can go through skin under force. Never for injecting. | Sharp | Sharp |
| Dead spaceDead space is the liquid left in the hub after the plunger bottoms out. Fixed-needle insulin syringes have almost none. Glossary | Low | Low |
| PricePrice tier is the rough position within its category, not a live price: budget is the cheapest sensible option, premium costs more for a reason the page explains. | Budget | Budget |
| TravelTravel says whether it is practical to fly with: carry-on means it goes through security without fuss. | Carry-on friendly | Carry-on friendly |
| SterileSterile means individually sealed and sterile until opened; anything that touches the inside of a vial or your skin should be. | Yes | Yes |
| PackPack is how many come in the listing this site links to; it is shown only where every store's listing gives the same count. Check it against the listing, since photos often show ten and ship one. | 100 | 100 |
| Reusable | No | No |
Which should you choose?
- Pick 31G if you draw small amounts (under 50 units) and want the finest needle; it comes on the 0.3 and 0.5 mL barrels, whose lines are easier to read.
- Pick 30G if you need the 1 mL barrel for larger draws, or if a thicker liquid draws slowly through 31G.
- Do not pick on gauge alone. Barrel size and marking increments change how accurately you can measure; gauge changes only how the needle feels.
The products
Open in the comparison tool Find the right syringe
Related guides
- Needle gauge chart: 18G to 32G, and what each is for
- 0.3, 0.5 or 1 mL insulin syringe: which size to buy
- How to read an insulin syringe
Common questions
Is 31G thinner than 30G?
Yes. Higher gauge numbers are thinner needles. 31G is one step thinner than 30G, and 32G thinner still.
Does a thinner needle hurt less?
A little, for most people; technique (room-temperature liquid, a fresh needle, slow injection) matters more than one gauge step.
Can I get 31G on a 1 mL syringe?
Rarely. Most 1 mL insulin syringes come with 29G or 30G needles; 31G is standard on the 0.3 and 0.5 mL barrels.
Last edited . Equipment only: nothing on this page is advice about what to inject, how much, or whether a product is fit to use. That comes from the product's labelling and whoever supplied it. Product pages link to your own country's Amazon store through affiliate links; your price is the same.