**6. Needle length**

In the last decade, insulin needle lengths have decreased dramatically. Previously, adults were given needles that were ≥ 8 mm long and children ≥6 mm. As shown in **Tables 1** and **2**, these lengths are now universally recognized as too long. They make IM injections more likely, and on the whole, the length of the needle has little or nothing to do with glucose control, according to a multitude of studies [8, 21–28]. Longer needles also tend to have larger diameters (smaller G or gauge), which correlates with a greater injection pain.

Hirsch [8] compared the 4-mm pen needle to 5- and 8-mm needles and showed the former to be safe and efficacious in adults (i.e., comparable glucose control); leakage from the skin was equivalent and both pain scores and overall preference were better with the 4 mm. In Japan, Miwa [29] compared the 4-mm needle with 6 mm and showed equivalent results, as did Nagai [30] when comparing 4-to 5-mm pen needles. Hirose [31] found equivalent modeled PK/PD results for the 4 mm compared to the 6- and the 8-mm needles, in young non-diabetics. Birkebaek [32] found a reduced IM risk with 4 versus 6-mm PNs in children and lean adults. Lo Presti [14] measured the skin and SC in children and adolescents with diabetes (ages 2–17) and concluded that the safest needle length for all ages is the 4 mm.

In obese adults, Bergenstal [33] recently showed that the 4-mm pen needles deliver equivalent glycemic control (HbA1c) to both 8- and 12.7-mm pen needles. These obese patients were taking relatively high doses of glargine (>40 IU), with total daily dose (TDD) insulin up to 300 U daily. No differences between 4- and both 8- and 12.7-mm PNs in hypo- or hyperglycemic events or insulin leakage were found in obese subjects with BMI up to nearly 60 kg/m2 . The 4-mm needle was found to be less painful, easier to use, easier to insert, and less anxiety-provoking than 8 or 12.7 mm (all at p < 0.05).

• The abdomen is the preferred site for soluble human insulin (regular), since absorption of

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http://dx.doi.org/10.5772/intechopen.76232

• The regular/NPH mix should be given in the abdomen to increase the speed of absorption of the short-acting insulin in order to cover postprandial glycemic excursions [18]. **A1**

• If there is risk of nocturnal hypoglycemia, NPH- and NPH-containing mixes given in the evening should be injected into the thigh or the buttock as these sites have slower absorp-

There are fewer studies of optimal delivery methods for the newer insulin analogs and GLP-1 s. However, insulin analogs are *not* as dependent on injection sites as are human insu-

• Rapid-acting insulin analogs may be given at any of the injection sites, as absorption rates

• Rapid-acting analogs should not be given IM although studies have shown that absorption rates are similar from fat tissue and resting muscle. Absorption from working muscle has

• Pending further studies, patients may inject long-acting insulin analogs in any of the usual injecting sites, with appropriate technique to prevent IM injection which can lead to pro-

• Pending further studies, patients using non-insulin injectable therapies should follow the recommendations already established for insulin injections with regards to needle length,

LH is the most common complication of insulin injection [59–62] or infusion [63, 64], with prevalence rates of 50% or higher. Risk factors for LH appear to be longer time on insulin, more daily injections, failure to carefully rotate injection sites, and extensive reuse of needles [59, 65–68]. The latter two risk factors are modifiable. Insulin injected into LH has been reported to have delayed or erratic absorption which may worsen glucose control, although these trials are older with less rigor, less precise insulin assays, or very small sample sizes

lins or NPH. From the existing studies, FITTER recommended the following:

this insulin is fastest there [35, 42–46]. **A1**

do not appear to be site-specific [49–53]. **A2**

not, however, been studied [50, 51, 54]. **A2**

site selection, and site rotation [56–58]. **A2**

found hypoglycemia [55]. **B2**

**10. GLP-1 agents**

**11. Lipohypertrophy**

tion of NPH [38, 47, 48]. **A1**

**9. Insulin analogs**

Based on these studies, FITTER recommended the following:

