Insulin Therapy and Administration Nursing
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Direct answer
Insulin is matched to meal patterns by its pharmacokinetics: rapid analogues (aspart, lispro) act within 10 to 15 minutes and are taken with food, regular insulin starts in about 30 minutes and is taken half an hour before meals, intermediate NPH peaks at 6 to 12 hours, and long analogues such as glargine last about 24 hours with no peak and cannot be mixed. Bedside craft runs on four rules — clear before cloudy when mixing, systematic rotation within one body region to prevent lipohypertrophy, in-use vials kept at room temperature for about 28 days and spare supplies at 2 to 8°C never frozen, and the 15-15 rule for hypoglycaemia below 70 mg per dL.
What you must remember
- Onset, peak, duration by class: rapid analogues 10 to 15 minutes, peak 1 to 2 hours, 3 to 5 hours total; regular insulin onset 30 minutes, peak 2 to 4, duration 5 to 8; NPH onset 1 to 2 hours, peak 6 to 12, duration 16 to 24; glargine about 24 hours with no pronounced peak; degludec beyond 24 hours.
- Timing with meals follows the class: rapid analogues immediately before or with the meal, regular insulin 30 minutes before food — and the tray must be present before the injection.
- Mixing rule: draw the clear (regular) insulin first, then the cloudy (NPH); glargine and detemir are never mixed with any other insulin.
- Storage: unopened vials and pens at 2 to 8°C until expiry; in-use cartridges or vials at cool room temperature for about 28 days, protected from light and heat; insulin that has frozen is discarded.
- Sites and rotation: abdomen absorbs fastest and most uniformly, then arm, thigh, buttock; rotate injections systematically within one region, because repeated same-spot injections create lipohypertrophy that both looks poor and absorbs erratically.
- Technique: inject at 90 degrees with a skin fold where needed, use 4 to 6 mm needles, leave the needle in briefly, and dispose of sharps without recapping.
- Hypoglycaemia (below 70 mg per dL): adrenergic signs of sweating, tremor, palpitations and hunger, then neuroglycopenic confusion — the 15-15 rule gives 15 grams of fast carbohydrate and rechecks in 15 minutes.
- The dawn phenomenon (early-morning hormone-driven hyperglycaemia) differs from the Somogyi effect (nocturnal hypoglycaemia with rebound); the discriminator is a 3 a.m. glucose check.
A mixed-dose morning and a ward hypoglycaemia
The order reads 12 units regular plus 18 units NPH before breakfast. The nurse rolls (never shakes) the NPH bottle to resuspend the crystals, cleans both vial tops, injects air into the NPH first, injects air into the regular vial and withdraws 12 units of clear insulin exactly, then withdraws cloudy NPH to the 30-unit total — the order of drawing is the examination point, because reversing it contaminates the regular vial. The injection goes into the abdomen, a centimetre or two from the last site, at 90 degrees with a pinch; breakfast is confirmed on the table, because regular insulin with a delayed tray is a planned hypoglycaemia. Two hours later, a patient on a sliding scale becomes sweaty with a meter reading of 52: the 15-15 rule applies — half a glass of juice, recheck in 15 minutes, repeat until above target, then a snack, since juice alone does not hold the glucose up. Had he been drowsy, nothing oral: intravenous dextrose or glucagon intramuscularly, airway watched, and the trigger sought — usually a meal that never arrived or a unit misread as millilitres.
Where students slip
The mixing order is the highest-frequency error, and the reasoning is worth knowing: regular insulin must stay uncontaminated, so cloudy-into-clear is forbidden. In-use pens are needlessly refrigerated, and frozen insulin is degraded and discarded, not thawed and used. The timing items trip on regular insulin being given "with meals" — it needs 30 minutes of lead. In hypoglycaemia items, the unconscious patient is given juice by mistake, and mild episodes are overtreated into hyperglycaemia instead of the 15-15 discipline with rechecking.
Frequently asked questions
Which insulin is drawn up first when mixing?
The clear short-acting (regular) insulin is drawn before the cloudy NPH, so that the intermediate insulin never contaminates the regular vial; glargine is not mixed at all.
What is the 15-15 rule?
For hypoglycaemia below 70 mg per dL, give 15 grams of fast-acting carbohydrate, recheck the glucose after 15 minutes, and repeat until above target, following with a snack if the meal is distant.
How is hypoglycaemia managed in an unconscious patient?
Nothing by mouth: intravenous 50% dextrose or glucagon 1 mg intramuscularly, airway positioned, glucose rechecked every 15 minutes and the cause sought.
Why must injection sites be rotated?
Repeated injection into the same spot causes lipohypertrophy — lumpy fat that absorbs insulin unpredictably, swinging glucose control; systematic rotation within one region prevents it.
Which site gives the fastest, most predictable absorption?
The abdomen, followed by the upper arm, thigh and buttock; consistency within one region matters more than the region itself.