Ultrasound-Guided Skin and Subcutaneous Fat Thickness Profiling for Insulin Delivery in Overweight and Obese Adults...

Safe insulin administration requires delivery into the subcutaneous tissue to avoid intradermal or intramuscular injection. Although international guidelines recommend the universal use of 4 mm needles, local anatomical data supporting this recommendation among overweight and obese adults with type 2 diabetes mellitus (T2DM) in Malaysia are limited.

To assess skin thickness (ST) and subcutaneous adipose tissue (SAT) using ultrasound to evaluate the safety of 4 mm insulin needles in overweight and obese adults.

This cross-sectional study involved 98 adults with T2DM on insulin therapy (body mass index [BMI] ≥23 kg/m²) attending a primary care clinic in Johor Bahru, Malaysia. ST and SAT at 10 abdominal injection sites and 8 upper arm injection sites were measured using ultrasonography. Data were analyzed using descriptive statistics, correlation tests, and multiple linear regression to identify associations with BMI, age, gender, and other variables.

The median abdominal ST was 2.46 mm (interquartile range [IQR]: 2.20-2.80), and upper arm ST was 1.92 mm (IQR: 1.73-2.11). Only 6.1% of participants had any site with ST greater than 4 mm. Median abdominal SAT was 16.75 mm (IQR: 14.83-19.28), and upper arm SAT was 15.38 mm (IQR: 12.10-17.73). Multiple linear regression showed that abdominal ST was significantly predicted by BMI (β = 0.244, p = 0.015) and inversely by age (β = -0.202, p = 0.040). Gender was the strongest predictor of upper arm ST (β = -0.418, p <0.001), with females having thinner skin. Abdominal SAT was positively associated with BMI (β = 0.469, p <0.001) and male gender (β = -0.205, p = 0.026), suggesting that BMI may serve as a useful clinical indicator of abdominal injection depth. No significant predictors were found for upper arm SAT.

Most overweight and obese Malaysian adults with T2DM have adequate ST and SAT for safe insulin delivery using 4 mm pen needles. Ultrasonographic data support individualized injection technique education in primary care, considering BMI, gender, and age.