You are ordered to prepare a mixture of regular insulin and NPH insulin. After injecting the required amount of air into the vials, you begin to withdraw the insulin into the syringe. The principles are

1. A

   NPH Insulin is filled first

2. B

   You must never mix NPH with regular insulin

3. C

   Regular insulin is filled first.

4. D

   The sequence of filling is not important

Appeared in: GMCH - 2015

Explanation

• The correct sequence for mixing insulins is to draw up the short-acting (Regular) insulin before the intermediate-acting (NPH) insulin.
• This procedure follows the well-established nursing mnemonic "Clear before Cloudy" or "RN" (Regular then NPH).
• The primary rationale is to prevent the NPH insulin, which contains added proteins (protamine), from contaminating the vial of pure Regular insulin.
• Contamination of the Regular insulin vial would alter its rapid onset of action, making its effect unpredictable and potentially leading to poor glycemic control and patient harm.

Why Other Options Were Wrong

• Option A: This is incorrect because drawing the cloudy NPH insulin first creates a significant risk of transferring it into the clear Regular insulin vial, which would contaminate the vial and alter the insulin's properties.
• Option B: This is incorrect. Regular and NPH insulins are compatible and are frequently mixed in one syringe to provide both short-term and intermediate-term glucose control with a single injection.
• Option D: This is incorrect and represents a dangerous practice. The sequence is critical for patient safety to ensure the predictable action of the short-acting insulin and maintain stable blood glucose levels.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Medication Administration: Mixing Insulins as background academic context rather than a clinical decision trigger.
• Correctly mixing insulin is a fundamental nursing skill essential for patient safety and effective diabetes management.
• Administering contaminated or improperly mixed insulin can lead to unexpected hypoglycemia or hyperglycemia, jeopardizing patient stability and potentially causing a medical emergency.
• Patient education is a key nursing responsibility. Nurses must be able to teach patients and their families how to mix insulins correctly and safely at home.

How to Approach the Question

• Identify the core task in the question: preparing a mixture of Regular and NPH insulin.
• Recall the physical properties of these insulins: Regular insulin is clear (short-acting), and NPH insulin is cloudy (intermediate-acting).
• Access the key safety principle for mixing insulins, often remembered by the mnemonic 'Clear before Cloudy' or 'RN' (draw up Regular first, then NPH).
• Understand the rationale behind this rule: to prevent the cloudy NPH from contaminating the clear Regular insulin vial, which would alter its action profile.
• Evaluate the options based on this principle. The option stating 'Regular insulin is filled first' directly matches the correct procedure.

Concept Tested & Keywords

• Concept Tested: Medication Administration: Mixing Insulins
• Stem keywords: mixture of regular insulin, NPH insulin, withdraw the insulin
• Lead-in keywords: The principles are
• Negative lead-in flag: false

Question ID

Q4ryxL5l2s8zVS658UTDEO

Copy ID

Reference Book

E6 Pharmacology Nursing Lilley 11e Part 2 p. 212-214