Key Takeaways
- Only Regular insulin can be given intravenously - all other insulins are subcutaneous only
- When mixing insulins, draw "Clear before Cloudy" (Regular before NPH) to prevent contamination
- Hypoglycemia signs include: cool/clammy skin, tremors, confusion, tachycardia - treat immediately with 15g fast-acting carbohydrate
- Long-acting insulins (Glargine/Lantus, Detemir/Levemir) should NEVER be mixed with other insulins
- Insulin is measured in units - always use an insulin syringe and have a second nurse verify high-alert doses
High-Alert Medications: Insulins
Insulin errors are among the most common and dangerous medication errors in healthcare. Understanding insulin types, administration, and monitoring is critical for the NCLEX and patient safety.
Insulin Types and Action Profiles
| Type | Examples | Onset | Peak | Duration |
|---|---|---|---|---|
| Rapid-Acting | Lispro (Humalog), Aspart (Novolog), Glulisine (Apidra) | 5-15 min | 30-90 min | 3-5 hours |
| Short-Acting | Regular (Humulin R, Novolin R) | 30-60 min | 2-4 hours | 5-8 hours |
| Intermediate | NPH (Humulin N, Novolin N) | 1-2 hours | 4-12 hours | 12-18 hours |
| Long-Acting | Glargine (Lantus), Detemir (Levemir) | 1-2 hours | No peak (flat) | 24 hours |
| Ultra Long-Acting | Degludec (Tresiba) | 1 hour | No peak | 42+ hours |
Critical Concept: Peak time = highest risk for hypoglycemia
IV Insulin Administration
Only Regular insulin can be given IV.
Indications for IV insulin:
- Diabetic ketoacidosis (DKA)
- Hyperglycemic hyperosmolar state (HHS)
- Critical illness requiring tight glucose control
IV insulin requires:
- Continuous cardiac monitoring
- Hourly blood glucose checks
- IV potassium replacement (insulin drives K+ into cells)
Mixing Insulins: "Clear Before Cloudy"
When mixing Regular and NPH in the same syringe:
- Inject air into NPH vial first (cloudy)
- Inject air into Regular vial (clear)
- Draw up Regular insulin first (clear)
- Draw up NPH insulin (cloudy)
Mnemonic: RN - Regular before NPH, or "Clear before Cloudy"
Rationale: If NPH contaminates the Regular vial, the entire vial is compromised because the action profile becomes unpredictable.
Insulins That Should NEVER Be Mixed
- Glargine (Lantus) - precipitates if mixed
- Detemir (Levemir) - altered absorption if mixed
- Degludec (Tresiba) - never mix
These long-acting insulins are given as separate injections.
Hypoglycemia Recognition and Treatment
Blood Glucose < 70 mg/dL = Hypoglycemia
| Signs/Symptoms | Body System |
|---|---|
| Tremors, shakiness | Sympathetic response |
| Tachycardia, palpitations | Cardiovascular |
| Diaphoresis (sweating) | Autonomic |
| Cool, clammy skin | Peripheral |
| Confusion, irritability | CNS - early |
| Seizure, unconsciousness | CNS - severe |
Treatment Protocol (Rule of 15):
- Give 15 grams of fast-acting carbohydrate
- Recheck blood glucose in 15 minutes
- Repeat if still < 70 mg/dL
- Once > 70, give protein/complex carb snack
Fast-Acting Carbohydrate Sources (15g each):
- 4 oz (120 mL) juice or regular soda
- 3-4 glucose tablets
- 1 tablespoon honey or sugar
- 6-7 hard candies
Unconscious Patient:
- Do NOT give anything by mouth (aspiration risk)
- Administer Glucagon 1 mg IM/SubQ
- Or Dextrose 50% (D50W) 25-50 mL IV push
Hyperglycemia Recognition
Blood Glucose > 250 mg/dL with ketones = Medical emergency
Signs of DKA:
- Kussmaul respirations (deep, rapid breathing)
- Fruity breath odor (ketones)
- Polyuria, polydipsia, polyphagia (3 P's)
- Nausea, vomiting, abdominal pain
- Altered mental status
Treatment: IV Regular insulin + IV fluids + electrolyte replacement
Administration Safety
| Safety Measure | Rationale |
|---|---|
| Use insulin syringe | Calibrated in units |
| Verify with 2nd nurse | Independent double-check |
| Check expiration date | Expired insulin loses potency |
| Rotate injection sites | Prevents lipodystrophy |
| Store properly | Opened vials room temp 28 days; unopened refrigerated |
| Never skip meals | Prevents hypoglycemia |
Timing of Administration
| Insulin Type | When to Give |
|---|---|
| Rapid-acting | With meals or within 15 minutes of eating |
| Regular | 30 minutes before meals |
| NPH | Same time daily; often morning and/or bedtime |
| Long-acting | Same time daily; often bedtime |
Sliding Scale Insulin
Sliding scale provides supplemental insulin based on blood glucose readings:
| Blood Glucose | Regular Insulin Dose |
|---|---|
| < 150 mg/dL | 0 units |
| 150-200 mg/dL | 2 units |
| 201-250 mg/dL | 4 units |
| 251-300 mg/dL | 6 units |
| 301-350 mg/dL | 8 units |
| > 350 mg/dL | 10 units + call provider |
Note: Actual scales vary by provider order
On the Exam
- Know which insulin can be given IV (Regular only)
- Recognize hypoglycemia symptoms
- Understand mixing order (clear before cloudy)
- Calculate insulin doses correctly
A patient receiving NPH insulin at 0730 is most at risk for hypoglycemia at what time?
The nurse is preparing to mix Regular and NPH insulin in the same syringe. Which action is correct?
A diabetic patient is found unresponsive with cool, clammy skin and blood glucose of 42 mg/dL. The priority intervention is:
Which insulin can be administered intravenously?