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| Factor | Effect on insulin pharmacokinetics | International recommendations on insulin delivery [141] |
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| Needle size | Age and gender, for example, have significant influence on the anthropometry in people with diabetes and should therefore be taken into account when choosing needle length and dosing strategy [158] in order to reduce the risk of intramuscular injection | Use of the shortest needles is recommended (the 4 mm pen and 6 mm syringe needle). In order to decrease the risk of intramuscular injections, the 4 mm needle should be used for injection in children and young adults. Lifting of a skinfold prior to injection or injection at a 45° angle may further reduce the risk of intramuscular injection |
| Time before withdrawal | Rapid withdrawal may result in loss of insulin and increased pharmacokinetic variability between injections [141] | With use of insulin pens, patients should count to 10 after the plunger is fully depressed before removing the needle from the skin |
| Dispersion | Dispersion of the injection volume gives rise to a more rapid absorption [108] | Larger doses may be split to reduce the volume of insulin and avoid leakage |
| Mixing | Inadequate resuspension is a problem with insulin suspensions (e.g., NPH insulin) and contributes to pharmacokinetic variability between injections [82, 141] | It is recommended to gently roll and tip cloudy insulin until the crystals are resuspended (the solution becomes milk white) |
| Needle reuse | Reuse of needles increases the risk of lipodystrophy [160, 161] | Reusing insulin needles is not an optimal injection practice, and patients should be discouraged from doing so |
| Rotation | Rotation between injection sites reduces the prevalence of lipodystrophy [141, 160, 161], but for a number of insulin preparations, rotation also elicits different pharmacokinetic and pharmacodynamic responses [111, 115, 118, 122–125, 130] | Patients should be encouraged to avoid injecting into areas of lipohypertrophy, and injections should be rotated by injecting at least 1 cm from previous injection (i.e., within the same injection region) |
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