Insulin
Types, mixing, injecting, and handling hypoglycemia
Insulin types (approximate times)
| Type | Examples | Onset | Peak | Duration | Notes |
|---|---|---|---|---|---|
| Rapid-acting | lispro, aspart, glulisine | ~15 min | 1–2 h | 3–5 h | Give within 15 min of a meal; food must be ready |
| Short-acting | regular | 30–60 min | 2–4 h | 5–8 h | 30 min before meals. Used in IV infusions (DKA) |
| Intermediate | NPH | 1–2 h | 4–12 h | 12–18 h | Cloudy: roll gently to mix; peak = hypoglycemia risk |
| Long-acting | glargine, degludec (detemir discontinued in the US) | 1–2 h | No real peak | ~24 h (degludec up to 42 h) | Basal dose. Never mix with other insulins |
Mixing NPH and regular in one syringe
- Inject air into NPH (cloudy). Don't draw up.
- Inject air into regular (clear) and draw up the regular dose.
- Then draw up the NPH dose.
Memory hook"Clear before cloudy", or R before N, like an RN. Never contaminate the clear vial with cloudy insulin.
Giving insulin
- Subcutaneous: abdomen (fastest, ≥2 in from the umbilicus), back of arms, thighs, buttocks.
- Rotate sites within an area (lumps of fat called lipohypertrophy cause erratic absorption).
- Pens: prime 2 units; hold the needle in for ~10 sec.
- High-alert: independent double check per policy; always use "units", never "U".
- Storage: unopened in the fridge (don't freeze); in-use pen or vial at room temperature for the time on the label (often 28 days).
Hypoglycemia (<70 mg/dL)
Signs: shaky, sweaty, fast heartbeat, anxious, hungry, headache, confused, irritable → seizures, coma. Beta blockers can hide the warning signs.
- Awake and can swallow: 15 g fast carbohydrate (4 oz/120 mL juice or regular soda, glucose tablets).
- Recheck in 15 min; repeat if still <70.
- Once normal: a snack or meal with protein and carbohydrate.
- Can't swallow or unconscious: glucagon (IM, SC or nasal) or IV dextrose; turn on the side.
In the hospital
- Typical target for most inpatients: 140–180 mg/dL.
- Basal + mealtime + correction insulin is preferred over sliding-scale insulin alone. Updated
- NPO: basal insulin is usually continued (often at a reduced dose): clarify with the prescriber; hold mealtime insulin.
- DKA drip: regular insulin IV; check K⁺ first (don't start if K⁺ <3.3: replace K⁺ first). Give SC basal insulin 1–2 h before stopping the drip.
Sick-day rules (type 1 and insulin users)
Keep taking basal insulin even if not eating; check glucose every 2–4 h and ketones if >240 mg/dL; drink fluids; call if vomiting, unable to keep fluids down, moderate/large ketones, or glucose staying high.
Morning highs
Dawn phenomenon: early-morning hormone surge raises glucose (2–3 AM glucose normal or high). Somogyi effect: night-time low followed by a rebound high (2–3 AM glucose low). Check a 2–3 AM glucose to tell them apart.