Insulin is meant to be injected into the fat layer just below the skin for consistant absorption.1

If you inject into a muscle, the insulin can work too quickly, which may lead to low blood sugar.2

The BD Nano™ 4-mm pen needle, BD's shortest pen needle yet, gets insult to the fat layer over 99.5% of the time, at all injection sites.3


References
  1. Vaag A., et al. Diabetes Care. 1990;13(1):74-6.
  2. Frid A., et al. Diabetes Care. 1990;13(1):473-7.
  3. Bigney MA, et al. Current Medial Research Opinion. 2010;26(6):1519-30.