An insulin syringe has four parts: a cap, a needle, a barrel, and a
The needle is short and thin and covered with a
fine layer of silicone to allow it to pass through the skin easily. A cap
covers and protects the needle before it is used.
The barrel is the
long, thin chamber that holds the insulin. The barrel is marked with lines to
measure the number of insulin units.
The plunger is a long, thin
rod that fits snugly inside the barrel of the syringe. It easily slides up and
down to push the insulin out through the needle. The plunger has a rubber seal
on the end that is inside the barrel, to prevent leakage. To measure the
required amount of insulin, you move the rubber seal until it matches the
correct line on the barrel.
Insulin syringes are made in several sizes.
Syringe size and insulin units
Number of units the
1/4 mL or 0.25 mL
1/3 mL or 0.33 mL
1/2 mL or 0.50 mL
Use the smallest syringe size you can for the dose of insulin you
need. The measuring lines on the barrel of small syringes are farther apart and
easier to see. When you choose the size of syringe, consider the number of
units you need to give and how well you can read the numbers on the barrel. A
0.25 mL or 0.33 mL syringe often is best for people who have poor eyesight,
because the numbers on the barrel are larger and easier to see.
Sarah Marshall, MD - Family Medicine & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator
How this information was developed to help you make better health decisions.