One needle size does not fit all: Skin to muscle depth for successful

  • Hemingway, S. (Speaker)
  • Jacqueline White (Contributor to Paper or Presentation)
  • Steve Lui (Contributor to Paper or Presentation)

Activity: Talk or presentation typesOral presentation


Intramuscular injection [IMI] practice is an essential nursing skill. Current practice relies on clinical judgement to determine needle length (unless specified in the medicine product licence). Obesity is increasing in the global population but guidelines have largely ignored how to select needle length to meet individual patient need.

b. Aim and objective/s of the study
Our aim was to systematically review the skin to muscle depth required to achieve injection into muscle in adults. Our objectives were to identify any implications of obesity status when selecting an appropriate needle length and site in clinical practice.

c. Search and review methodology
We performed our review according to the PRISMA statement. Studies of subjects above the age of 18 years using observational or experimental designs where the distance from the skin to muscle had been measured at any IMI site, and obesity status was reported were included in our search strategy. The primary outcome of interest was the distance from skin surface to muscle penetration.

d. Findings
13 studies were identified that investigated the dorsogluteal, ventrogluteal, deltoid and vastus lateralis sites, all used cross sectional observational designs. Nine used ultrasound, five computer tomography and one magnetic resonance imaging. Obesity status was reported as BMI or hip to waist ratio. In all studies there was a correlation between obesity status and the distance from skin surface to muscle. In females this exceeded 37mm at both gluteal sites, independent of obesity status.

e. Conclusions and implications
There should be an assessment of obesity status before selecting needle length for intramuscular injections in both genders. Needles greater than the standard 37mm length are recommended for all females, whatever their obesity status for any gluteal site. Injections into gluteal sites should be avoided in females who are obese. Deltoid injections are more likely to achieve muscle penetration in both genders, and in patients who are overweight or obese. Further high-quality research is required.
Period4 Mar 2020
Event titleTrinity Health and Education International Research Conference: 'Integrated healthcare: Developing person-centred health systems’
Event typeConference
LocationDublin, IrelandShow on map
Degree of RecognitionInternational