title: Intramuscular risk at insulin injection sites--measurement of the distance from skin to muscle and rationale for shorter-length needles for subcutaneous insulin therapy.
abstract: BACKGROUND
  Intramuscular (IM) injection can increase insulin absorption, causing hypoglycemia. Available needle lengths today are 4-12.7 mm for pens and 6-12.7 mm for syringes. We describe the distance (D) from skin surface to muscle fascia at injection sites for subcutaneous (SC) insulin therapy and recommend needle lengths to reduce IM injection risk.
  
  
  METHODS
  At two locations in the United States, skin and SC fat thicknesses were measured by ultrasound at the abdomen, arm, thigh, and buttock in diverse adults (body mass index [BMI] range, approximately 19-65 kg/m²) with diabetes (n=341 with one or more paired skin and SC measurement, permitting calculation of D). The natural log of D by body site, BMI, and gender were analyzed using a mixed model to estimate IM risk.
  
  
  RESULTS
  D varied significantly by body site, BMI, and gender (each P<0.001), increasing with higher BMI and in women. Median D ranged from 10.9 mm (95% confidence interval, 10.3, 11.6) at the thigh to 16.9 mm (15.9, 18.1) at the buttock. Minimum D was <3 mm at the thigh and <5 mm elsewhere. When inserted 90° without pinch-up, the most commonly used needle worldwide (8 mm) has estimated IM risks of 25% and 9.7%, respectively, in the thigh and abdomen, versus 1.6% and 0.1%, respectively, with a 4 mm needle. A 45° insertion reduces, but does not eliminate, IM risk with longer needles.
  
  
  CONCLUSIONS
  Gender, BMI, and body site affect D; when combined with needle length and insertion angle, these factors permit detailed estimates of IM insulin injection risk. Such risk varies across sites, appears greatest at the thigh, is unnecessarily increased with 8 mm and 12.7 mm needles, and is greatly reduced with shorter-length needles and good injection technique.
authors.affiliation: Diabetes Care , BD, Franklin Lakes, New Jersey.
authors.forename: Laurence
authors.initials: L
authors.lastname: Hirsch
authors.forename: Karen
authors.initials: K
authors.lastname: Byron
authors.forename: Michael
authors.initials: M
authors.lastname: Gibney
mesh_terms: D050154:Adiposity; D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D048909:Diabetes Complications / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D007049:Iatrogenic Disease / Q000453:epidemiology / Q000517:prevention & control; D007279:Injections, Subcutaneous; D007328:Insulin / Q000008:administration & dosage / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000187:drug effects / Q000293:injuries; D009135:Muscular Diseases / Q000139:chemically induced / Q000453:epidemiology / Q000517:prevention & control; D016602:Needlestick Injuries / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000517:prevention & control*; D050177:Overweight / Q000150:complications / Q000000981:diagnostic imaging; D061214:Patient Safety; D012306:Risk; D012867:Skin / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000293:injuries; D050151:Subcutaneous Fat / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000293:injuries; D040521:Subcutaneous Tissue / Q000000981:diagnostic imaging / Q000187:drug effects / Q000293:injuries; D014463:Ultrasonography; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin