• People of all ages:

• the route of injection — whether it is intramuscular or subcutaneous
• the anatomic site of the injection

• Infants and children:

• age must also be considered

• Adults:

• weight will also need to be taken into account

Below is a summary of the guidance for choosing the proper needle length for intramuscular and subcutaneous injections based on CDC’s General Best Practice Guidelines for Immunization (Vaccine Administration).

FOR INFANTS, CHILDREN, AND TEENS

Intramuscular (IM) injections: Injection site and needle size

• For newborns (0–28 days): Use anterolateral thigh muscle, ⅝" needle, 22–25 gauge
  Note: For neonates (first 28 days of life) and preterm infants, a ⅝" needle is recommended if the skin is stretched flat between the thumb and forefinger and the needle is inserted at a 90° angle to the skin.
   
• For infants (1–12 months): Use anterolateral thigh muscle, 1" needle, 22–25 gauge
   
• For toddlers (1–2 years): There are two options for injection site and needle length:
  • Anterolateral thigh muscle – use 1"–1¼" needle, 22–25 gauge
  • Deltoid muscle – if muscle mass adequate, use ⅝"–1" needle, 22–25 gauge
     
• For children (3–10 years): There are two options for injection site and needle length:
  • Deltoid muscle – use ⅝"–1" needle, 22–25 gauge
  • Anterolateral thigh muscle – use 1"–1¼" needle, 22–25 gauge
     
• For preteens and teens (11–18 years): There are two options for injection site and needle length:
  • Deltoid muscle – use ⅝"–1" needle, 22–25 gauge
  • Anterolateral thigh muscle – use 1"–1½" needle, 22–25 gauge

Subcutaneous (Subcut) injections: Injection site and needle size

• For infants (11–12 months): Inject at a 45° angle into fatty tissue overlying the anterolateral thigh muscle – use ⅝" needle, 23–25 gauge
   
• For children and teens (1–18 years): Inject at a 45° angle into fatty tissue overlying the triceps or anterolateral thigh muscle – use ⅝" needle, 23–25 gauge

FOR ADULTS

Intramuscular (IM) injections

The deltoid muscle is most often used as the site for IM injections in adults. Needle length is usually 1"–1½", 22–25 gauge, but a longer or shorter needle may be needed depending on the patient's weight.

Note: An alternate site for IM injection in adults is the anterolateral thigh muscle. The needle length and gauge are the same as when the deltoid muscle is used, i.e., 1"–1½" length, 22–25 gauge.

You should choose needle length based on the weight of your adult patients, as follows:

• Adults weighing less than 130 lbs (60 kg): Use of a 1" needle is recommended. However, a ⅝" needle may be used for IM injection in the deltoid muscle if the fatty tissue overlying the deltoid muscle is flattened (i.e., not bunched between thumb and fingers during the injection) and the needle is inserted at a 90° angle to the skin.
   
• Adults weighing 130–152 lbs (60–70 kg): Use of a 1" needle is recommended.
   
• Women weighing 152–200 lbs (70–90 kg) and men weighing 152–260 lbs (70–118 kg): Use of a 1"–1½" needle is recommended.
   
• Women weighing more than 200 lbs (90 kg) or men weighing more than 260 lbs (118 kg): Use of a 1½" needle is recommended.

Subcutaneous (Subcut) injections

• Inject at a 45° angle into fatty tissue overlying the triceps muscle – a ⅝" needle, 23–25 gauge is recommended.

MORE RESOURCES

Administering Vaccines: Dose, Route, Site, and Needle Size

Administering Vaccines to Adults: Dose, Route, Site, and Needle Size

How to Administer Intramuscular and Subcutaneous Vaccine Injections

How to Administer Intramuscular and Subcutaneous Vaccine Injections to Adults

IAC’s Handouts: Administering Vaccines gateway page

IAC’s Clinic Tools: Administering Vaccines gateway page

CDC Vaccine Administration gateway page

CDC Vaccine Administration Resource Library with instructive videos on vaccine administration

CDC Epidemiology and Prevention of Vaccine-Preventable Diseases (“The Pink Book"), Chapter 6, Vaccine Administration: Route and Site