Needle Length for Deltoid Injection


Synopsis: It may be appropriate to obtain a patient’s weight and choose a needle of the correct length to assure mid-deltoid delivery of vaccine.

Source: Poland GA, et al. Determination of deltoid fat pad thickness. JAMA 1997;277:1709-1711.

Vaccines are a major focus of travel medicine, and proper technique in administering them is important for immunogenicity and to decrease side effects. In a study from the Mayo Clinics, the deltoid fat pad thickness (DFPT) was measured with the goal of deciding the appropriate needle length to assure intramuscular administration of vaccine.

Health care personnel who were being given hepatitis B vaccine had skin to muscle distance (DFPT) and muscle to bone distance (deltoid muscle thickness) measure by ultrasound. In addition, their weight, height, and mid-deltoid circumference were determined. There were 94 men and 126 women. Men and women had the same body mass index, but women consistently had a greater DFPT (mean, 11.7 mm vs 8.3 mm; P < 0.001) and men had greater deltoid muscle thickness. For women, the DFPT varied by weight. For men in the weight ranges studied (59-118 kg), a needle length of 25 mm (1 in) was needed to penetrate the deltoid muscle by 5 mm (See table). A 16 mm (5/8 in) needle would not have been long enough in 17% of the men. For women who weighed less than 60 kg, a 16 mm (5/8 in) needle was adequate; for those 60-90 kg, a 25 mm needle was needed; and for women more than 90 kg, a 38 mm (1.5 in) needle was required. These needle lengths took into account the authors’ recommendation that the needle not be inserted to the hub, but that 2-3 mm be left exposed at the skin.


Needle Length Recommendation for Intramuscular Immunization*

Age or Weight Needle Length Site

Very young or small infants 16 mm (5/8 in) Anterolateral thigh

Average 4-month-old 22-25 mm (7/8-1 in) Anterolateral thigh

Toddlers and older childre22-25 mm (7/8-1 in) Anterolateral thigh or deltoid (if sufficient muscle mass)

Adolescents and adults Deltoid

Men 59-118 kg 25 mm (1 in)


< 60 kg 16 mm (5/8 in)

60-90 kg 25 mm (1 in)

> 90 kg 38 mm (1.5 in)

* Adapted from: Poland GA, et al. JAMA 1997;277:1709-1711 and References 5 and 6.


Administration of vaccine into the substance of muscle is necessary to assure immunogenicity and to potentially decrease side effects. The importance of intramuscular administration has been clearly shown with hepatitis B vaccination. Individuals who received vaccine in the gluteal region had lower frequencies of seroconversion,1 and the reason for this was felt to be failure to inject vaccine into muscle.2 While there are multiple other reasons for variability in the immunogenicity of vaccines such as age, gender, smoking status, obesity, and concomitant disease,3,4 the effort to assure intramuscular administration of vaccine remains important.

The current study provides guidelines for needle length use in adults. (See table.) While there are some limitations of the study, such as that the individuals vaccinated were all healthy (potentially limiting a wide range of weights) and all were younger than 60 years of age, the authors’ recommendations fall within accepted guidelines.5 For children, the American Academy of Pediatrics has published guidelines that should be followed.6 (See table.)

For practical purposes in the travel clinic, it may be appropriate to obtain a patient’s weight and choose a needle of the correct length to assure mid-deltoid delivery of vaccine.


1. Ukena T, et al. Site of injection and response to hepatitis B vaccine (letter). N Engl J Med 1985;313:579-580.

2. Shaw FEJ, et al. Effect of anatomic injection site, age, and smoking on the immune response to hepatitis B vaccination. Vaccine 1989;7:425-430.

3. Roome AJ, et al. Hepatitis B vaccine responsiveness in Connecticut public safety personnel. JAMA 1993; 270:2931-2934.

4. Wood RC, et al. Risk factors for lack of antibody following hepatitis B vaccination in Minnesota health care workers. JAMA 1993;270:2935-2939.

5. Centers for Disease Control and Prevention. General recommendations on immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 1994;43 (No. RR-1):1-38.

6. American Academy of Pediatrics. Vaccine Administration. In: 1997 Red Book: Report of the Committee on Infectious Diseases. Peter G (ed.) Elk Grove Village, IL: American Academy of Pediatrics; 1997:9, 14-15.