Insulin Administration Technique
Drawing up two insulins in the wrong order can destroy an entire vial — and the wrong injection technique can turn rapid-acting insulin into something dangerously unpredictable.
Core Concept
Insulin is administered subcutaneously at a 90-degree angle (or 45 degrees for thin clients) into rotating sites: abdomen (fastest absorption), arms, thighs, and buttocks (slowest). Site rotation within the same anatomic region prevents lipodystrophy while maintaining predictable absorption. When mixing insulins in one syringe, always draw up clear (regular) before cloudy (NPH) — "clear before cloudy." This protects the regular insulin vial from contamination with NPH, which would alter its onset. Roll NPH gently between palms to resuspend — never shake, as this denatures the protein and creates air bubbles. Opened insulin vials are stable at room temperature for 28 days; refrigerated until first use. Inject at room temperature to reduce pain and ensure consistent absorption. After injection, do not massage the site — this accelerates absorption unpredictably. For pen devices, hold the needle in the skin for 10 seconds after injection to ensure full dose delivery. Only regular insulin may be given IV; all other formulations are subcutaneous only.
Watch Out For
Don't confuse injection site rotation (moving within the same region, e.g., different spots on the abdomen) with switching regions entirely each dose — same-region rotation maintains consistent absorption. Students mix up the mixing rule: clear (regular) is drawn first into the syringe, then cloudy (NPH) is drawn second. Never mix long-acting analogs (glargine, detemir) with any other insulin — they cannot be combined in the same syringe.
Clinical Pearl
Clear before cloudy, roll don't shake, abdomen absorbs fastest. If you contaminate the regular vial with NPH, that vial is ruined.
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