Insulin therapy
A clinical reference covering insulin types and pharmacokinetics, basal-bolus regimen design, dose titration, adjustment in renal impairment, and hypoglycaemia recognition and management.
Insulin preparations: onset, peak, and duration
| Type | Examples | Onset | Peak | Duration | Use |
|---|---|---|---|---|---|
| Rapid-acting analogue | Aspart (NovoRapid), Lispro (Humalog), Glulisine (Apidra) | 5–15 min | 1–2 h | 3–5 h | Meal bolus |
| Short-acting (regular) | Actrapid, Humulin R | 30–60 min | 2–4 h | 6–8 h | Meal bolus (30 min pre-meal); IV infusions |
| Intermediate (NPH) | Insulatard, Humulin NPH | 2–4 h | 4–10 h | Up to 18 h | Basal BD or combined with rapid-acting |
| Long-acting analogue | Glargine U100 (Lantus), Glargine U300 (Toujeo) | 2–4 h | Peakless | 24 h | Basal once daily |
| Long-acting analogue | Detemir (Levemir) | 1–3 h | Minimal | ~20 h | Basal OD or BD |
| Ultra-long analogue | Degludec (Tresiba) U100/U200 | ~1 h | Peakless | 42+ h | Basal OD; flexible timing |
| Pre-mixed | NovoMix 30, Humulin 70/30 | Dual | Dual | Variable | Fixed-ratio BD regimens |
Basal-bolus regimen: structure and titration
Basal-bolus therapy provides near-physiological insulin replacement by combining a long-acting insulin (basal) with rapid-acting insulin at each meal (bolus). It is the standard intensive regimen for type 1 diabetes and the preferred intensive regimen for type 2 diabetes when oral/non-insulin agents are insufficient.
Starting doses
Total daily dose (TDD): 0.3–0.5 units/kg/day in insulin-naive patients (lower end for elderly or renal impairment). Split: 50% basal (long-acting, once daily at bedtime or morning) + 50% bolus (divided equally before each of 3 meals). In clinical practice, doses are increased in 2-unit increments every 2–3 days.
Titration targets
Basal dose: titrate to fasting glucose 4.4–7.2 mmol/L (80–130 mg/dL) per ADA Standards of Care ↗. Bolus dose: titrate to 2-hour postprandial glucose <10 mmol/L. Insulin-to-carbohydrate ratio (ICR): starting estimate 500 ÷ TDD (grams carb per 1 unit). Correction factor (ISF): 1700 ÷ TDD (mg/dL) or 94 ÷ TDD (mmol/L).
Sick day rules
Never stop insulin entirely during illness — counter-regulatory hormones increase glucose and ketone production. Continue basal insulin at 80% of usual dose; adjust bolus to match any eating. Check blood glucose every 2–4 h. Check ketones if BG >14 mmol/L (250 mg/dL). Sick day rules are detailed in ADEA/Diabetes Australia guidelines ↗.
Storage and injection technique
Unopened insulin: refrigerate 2–8°C; do not freeze. In-use pens/vials: room temperature up to 28–30 days (product-specific). Rotate injection sites (abdomen, thigh, upper arm, buttock) within and between sites to prevent lipohypertrophy — a common cause of erratic absorption. See Forum for Injection Technique recommendations (NCBI PMC) ↗.
Hypoglycaemia: classification and treatment
| Level | Definition | Symptoms | Treatment |
|---|---|---|---|
| Alert value | BG <3.9 mmol/L (<70 mg/dL) | May be asymptomatic — action required | 15g fast-acting carbohydrate; recheck in 15 min |
| Clinically significant | BG <3.0 mmol/L (<54 mg/dL) | Sweating, tremor, palpitations, confusion | 15–15 rule; follow with complex carb if meal >1 h |
| Severe | Requires assistance from another person | Impaired consciousness, seizure, coma | Glucagon IM/SC 1 mg; or IV dextrose 50% 25 mL; call emergency services |
15–15 rule: 15 g fast-acting carbohydrate (4 glucose tablets = 150 mL regular juice = 6 jelly beans) → wait 15 min → recheck BG → repeat if still <3.9 mmol/L. Sources: ADA Standards 2026 ↗, Diabetes Canada hypoglycaemia guidelines ↗.