Chart — Pharmacology
Insulin Clinical Decision Chart
Clinical decision support for insulin selection — advantages, disadvantages, typical use cases, hypoglycemia risk, and dosing flexibility by insulin type. For onset/peak/duration pharmacokinetics, see the Insulin Types Chart.
Educational use only. Insulin is a high-alert medication. Selection, dosing, and timing require a provider order and independent two-nurse verification per institutional policy. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Clinical Comparison at a Glance
| Type | Primary Use | Hypo Risk | Dosing Flexibility | Can Mix? | IV Use? |
|---|---|---|---|---|---|
| Rapid-Acting | Prandial bolus; insulin pump | High (peak 1–2 hr) | High — within 15 min of meal | With NPH (some preparations) | No |
| Regular | IV insulin (DKA); sliding scale; prandial | Moderate-High (peak 2–4 hr) | Low — 30 min pre-meal required | With NPH (clear before cloudy) | Yes — only insulin for IV |
| NPH | Basal coverage (BID); mixed regimens | High (pronounced peak 6–12 hr) | Low — timing critical | With Regular; rapid-acting (some) | No |
| Glargine | Basal (once daily) | Low (no peak) | Moderate — same time daily | Never mix | No |
| Detemir | Basal (once or twice daily) | Low (minimal peak) | Moderate — same time daily | Never mix | No |
| Degludec | Basal with flexible schedule | Very Low (ultra-flat, no peak) | Very High — ±8 hr window | Never mix | No |
Advantages and Disadvantages by Type
Rapid-Acting
Lispro (Humalog), aspart (NovoLog), glulisine (Apidra)
- Closely mimics physiological post-meal insulin spike
- Can be given immediately before (or just after) a meal — flexible timing
- Short duration reduces stacking risk between doses
- Can be used in insulin pumps (CSII)
- Must be paired with a meal — if meal is delayed or withheld, hypoglycemia risk is high
- Requires frequent glucose monitoring
- Higher cost than Regular insulin
Prandial (mealtime) coverage in basal-bolus regimens; correction doses; insulin pumps
High — peak within 1–2 hrs; hypo occurs when patient does not eat after injection
High — timing flexible within 15 min of meal
Short-Acting (Regular)
Regular insulin (Humulin R, Novolin R)
- Only insulin approved for IV administration — essential for DKA protocols
- Can be mixed with NPH (regular drawn first)
- Lower cost than analog insulins
- Used for sliding-scale coverage
- Slower onset requires 30-min pre-meal timing — harder to coordinate with meal delivery
- Longer duration increases overlap and stacking risk between doses
- Not as physiologically matched as rapid-acting analogs for meal coverage
IV insulin infusions (DKA/HHS management), sliding-scale coverage, mixed with NPH in 2-dose regimens
Moderate-high — peak at 2–4 hrs; risk if meal is missed after dose
Low — 30-min pre-meal timing is required
Intermediate-Acting (NPH)
NPH insulin (Humulin N, Novolin N)
- Provides basal-like coverage when given twice daily
- Can be mixed with Regular insulin (cost-effective combination)
- Lower cost than long-acting analogs
- Long clinical track record
- Pronounced peak at 6–12 hrs creates predictable hypoglycemia window (especially overnight with PM dose)
- Variable absorption — more unpredictable than long-acting analogs
- Requires consistent injection timing to avoid gaps in coverage
- Must be resuspended (roll, not shake) before each use
Background basal coverage (twice daily), mixed with Regular in fixed 70/30 regimens, cost-sensitive patients
High — pronounced peak; overnight hypoglycemia is a significant concern with evening NPH dose
Low — timing critical due to peak-driven hypoglycemia risk
Long-Acting (Basal)
Glargine (Lantus, Basaglar, Toujeo), detemir (Levemir)
- Flat, peakless profile — lower and more predictable hypoglycemia risk vs. NPH
- Once-daily dosing (glargine); consistency reduces adherence burden
- Stable 24-hr basal coverage without pronounced peak
- Continue even during NPO status (typically at reduced dose per provider order)
- Cannot be mixed with any other insulin — separate injection required
- Higher cost than NPH
- Glargine and Regular are both clear — label mix-up risk if not verified
- Toujeo (U-300 glargine) is not substitutable 1:1 with standard glargine
Basal coverage in basal-bolus regimens; Type 1 diabetes; Type 2 with inadequate oral agent control
Low — no pronounced peak; hypoglycemia still possible from accumulation or dose error
Moderate — same time daily preferred; some flexibility within a few hours
Ultra Long-Acting
Degludec (Tresiba U-100, U-200)
- Longest duration (> 42 hr) and flattest peakless profile available
- Flexible dosing window — same time each day with ±8 hr window acceptable
- Lowest day-to-day variability of any basal insulin
- Ideal for patients with irregular schedules or shift work
- Cannot be mixed with any other insulin
- Highest cost among basal insulins
- Very long half-life means dose errors have prolonged consequences
- Cannot be rapidly titrated — changes take days to reach steady state
Basal insulin for patients who need flexible dosing schedules; brittle diabetes; patients with frequent NPO status
Very low — ultra-flat profile; but duration means any hypoglycemia may be prolonged
Very high — ±8 hr dosing window; can vary daily
Basal-Bolus Insulin Therapy
The physiological insulin secretion pattern has two components: basal (continuous low-level secretion throughout the day to suppress hepatic glucose production) and bolus (sharp spikes after each meal). Modern insulin regimens replicate this pattern.
Standard Basal-Bolus Regimen:
- Basal insulin: Long-acting (glargine, detemir, or degludec) given once daily — provides the 24-hr background coverage
- Bolus insulin: Rapid-acting (lispro, aspart, or glulisine) given before each meal — covers post-meal glucose rise
- Correction dose: Additional rapid-acting based on current glucose, per sliding scale or correction factor
NPH-based regimens (NPH + Regular given BID) were the predecessor to basal-bolus therapy. They are still used in cost-sensitive settings but have less predictable pharmacokinetics than analog-based regimens.
Insulin Mixing — Clinical Rules
Can mix: Regular + NPH
Draw Regular (clear) first — inject air into NPH vial, then withdraw Regular, then add NPH. “Clear before cloudy.” Administer immediately. Prevents NPH contaminating Regular and slowing its onset.
Cannot mix: Glargine, Detemir, Degludec
These long-acting analogs are formulated at an acidic or neutral pH that is disrupted by mixing. Mixing changes their pharmacokinetic profile, making absorption unpredictable. Each requires a separate injection.
Rapid-acting + NPH: conditionally compatible
Lispro and aspart can be mixed with NPH in some preparations — but always follow manufacturer guidance and institutional protocol. Glulisine should not be mixed with NPH per manufacturer labeling.
Key Decision-Point Safety Reminders
- Insulin is a high-alert medication — independent two-nurse verification is required before every dose
- Glargine and Regular are both clear solutions and look identical — label verification every time is non-negotiable
- Never give rapid-acting insulin to an NPO patient without a provider order — confirm the patient will eat
- Regular insulin is the only insulin that can be given IV — this is non-negotiable for DKA management
- Hold insulin and notify provider for blood glucose < 70 mg/dL before administration (or per institutional threshold)
- Long-acting insulin is typically continued at reduced dose during NPO periods — always verify with provider
- Toujeo (glargine U-300) and standard glargine (U-100) are not interchangeable on a 1:1 unit basis
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with Academy of Medical-Surgical Nurses (AMSN) · Current medical-surgical nursing standards. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →