An insulin syringe has three parts: a needle, a barrel, and
The needle is short and thin and covered with a
fine layer of silicone to allow it to pass through the skin easily and lessen
pain. A cap covers and protects the needle before it is used.
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 either draw the insulin into the barrel or push the
insulin out of the barrel through the needle. The plunger has a rubber seal at
the lower end to prevent leakage. The rubber seal is matched with the line on
the barrel to measure the correct amount of insulin.
Insulin syringes are made in several sizes.
Syringe size and units
units the syringe holds
1/4 mL or 0.25
1/3 mL or 0.33
1/2 mL or 0.50
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 see the markings on
A 0.25 mL or 0.33 mL syringe usually is best for
children (who often need very small doses of insulin) and for people with poor
A 1 mL syringe may be best for an adult who needs to take
a large amount of insulin.
How this information was developed to help you make better health decisions.