**2. Current insulin delivery practice**

A large survey of current insulin delivery has shown that there are many aspects of injection practice which are suboptimal [5, 6]. For decades, professionals had been advising patients to use insulin needles which, we now know, were too long for them, with no scientific rationale. However, after the shortest pen needles (4 mm) became available and studies on injection site anatomy and needle performance began to be published, starting in 2010 [7, 8], showing the safety and efficacy of these needles, the recommendations of experts changed. It was recognized that 4-mm pen needles were the optimal choice for nearly all injecting patients, whether adults or children: thin, normal-weight or obese, male or female, and of all ethnicities. These needles were felt to be a key step toward reducing the risk of IM injections. As a result, the use of the 8-mm needle, the dominant size in 2010, has decreased dramatically since then, with a corresponding increase in the use of the 4-mm needle.

However, the latest survey revealed that the longer lengths (8 mm and higher) are still being used by approximately 30% of patients worldwide and that the 5- and 6-mm needles are still used by approximately 20% each. This means that only 30% of patients worldwide currently use the recommended 4-mm needles. Longer needles are being used in sites where IM injection risk is very high (thighs and arms) and by patients who are at an increased risk because they have thin SC layers (slim and normal-weight adults as well as all adolescents and children).

The same survey has shown that lipohypertrophy (LH) is very common at injection sites. LH was found in almost a third of patients worldwide, many of them having LH at multiple injection sites. Injecting into LH has serious consequences for glucose control as well as possibly adverse effects on long-term outcomes and costs. Patients with LH consume a mean of over 10 IU more insulin per day than those without LH, and their HbA1c is on average 0.55% higher. LH is associated with increased rates of unexplained hypoglycemia, glucose variability, and more frequent diabetic ketoacidosis (DKA).

The survey showed that LH is most frequently associated with an incorrect rotation of injection sites and reusing pen needles. Rotating injection sites carefully appears to be the best method of avoiding LH. HbA1c values are lower in patients who rotate their injections over larger injection areas and who get their sites inspected regularly. Checking of injection sites routinely by health-care givers is associated with less LH and lower HbA1c levels, yet nearly 40% of patients reported that they could not remember their injection sites ever being examined. Patients are also more likely to rotate correctly if they have obtained injection instruction from their carer in the last 6 months. However, less than two out of five claim to have obtained such instructions on injecting in that time period. Ten percent of total injectors claim that they have never obtained injection training at all. The survey also shows that incorrect disposal of sharps after use is rampant. The majority of used sharps end up in public trash and constitute a major risk factor for accidental needle sticks.
