Insulin therapy is essential for type 1 diabetes. While a reasonable glycemic control prevents complications, inadvertent intramuscular (IM) insulin injection results in hypoglycemia and fluctuations of blood glucose levels.

To assess the subcutaneous thickness (SCt) at the potential insulin injection sites, in order to determine the suitable needle length.

Diabetic and non-diabetic children (n=125; aged 2–14 years) attending a tertiary care hospital were examined, after excluding those who had skin abnormality at the injection site, were hospitalized for>3 days, or had any other chronic illnesses. Dermal thickness (Dt) and SCt at the potential insulin injection sites were measured with ultrasonography.

The mean age of the patients was 8 years and 57% were boys; mean Dt was 2.1±0.4 mm, SCt was 7.45.6±3.7 mm, and maximum SCt was 29.8 mm in the anterior abdominal wall. SCt increased with age and by raising a skin fold (sf). There was no difference (P>0.05) in Dt between genders, and limbs showed thinner Dt values than the abdomen. SCt changed with the injection site: it was the lowest in the thigh and the highest in the abdomen. SCt was thicker in females, with or without sf (P<0.001). For all sites, IM risk was high for 15-mm needles: it was highest in the thighs (98%) and reduced to 86% with sf. IM risk was low for 5-mm needles: it was highest in the thigh (38%), and reduced to 12% with sf. Compared with girls (up to 42%), IM risk was higher for boys (up to 54%), even for 5-mm needles with a sf.

Using a short needle is recommended for children, particularly for boys. Regardless of the needle length, the raised sf technique is associated with reduced IM risk.