# A nurse is preparing to administer heparin 5,000 units subcutaneously every 12 hours. The available heparin concentration is 10,000 units/mL. How many mL should the nurse administer per dose?

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## 문제

A nurse is preparing to administer heparin 5,000 units subcutaneously every 12 hours. The available heparin concentration is 10,000 units/mL. How many mL should the nurse administer per dose?

## 보기

1. 1 mL
2. 2 mL
3. 0.25 mL
4. 0.5 mL **✔ 정답**

**정답: 4**

## 해설

Using the formula: Dose ordered ÷ Dose available × Volume = 5,000 units ÷ 10,000 units/mL × 1 mL = 0.5 mL. This calculation ensures safe administration of heparin, a high-alert medication.

## 심화 해설

Understanding the Prescription and Supply

The provider has ordered heparin 5,000 units to be given subcutaneously every 12 hours. The vial you have on hand contains a concentration of 10,000 units/mL. This means that for every 1 mL of liquid in the vial, there are 10,000 units of heparin.

Performing the Dosage Calculation

To find the volume in mL to administer, you can use the standard formula method, which is a fundamental nursing proficiency for safe medicine administration [1]. The formula is:

(Desired Dose / Available Concentration) = Volume to Administer

Plug the values from the order and the medication label into the formula:

Desired dose (D) = 5,000 units

Available concentration (H) = 10,000 units / 1 mL

Calculation: (5,000 units / 10,000 units) × 1 mL = 0.5 mL

The result is 0.5 mL. The nurse should administer 0.5 mL of the heparin solution to deliver the prescribed dose of 5,000 units.

Clinical Significance of Accurate Calculation

Performing this calculation with utmost care is a non-negotiable element of patient safety. Inaccurate medicine dosage calculations are a significant causative factor in medication errors, which can lead to severe patient harm [1]. For a high-alert medication like heparin, an error in this calculation could result in a massive overdose. For instance, if a nurse mistakenly administered 1 mL instead of 0.5 mL, the patient would receive 10,000 units, doubling the intended dose and substantially increasing the risk of a critical bleeding event. Competence in this skill relies not only on understanding the mathematical formula but also on the nurse's ability to manage factors like mathematics anxiety, which can impair calculation accuracy in clinical settings [2]. A systematic approach, such as double-checking the calculation and having another nurse independently verify the dose, is a standard safety practice that helps mitigate the risk of error before the medication reaches the patient.References (research sources)

- [1]How to undertake oral medicine dosage calculations.Research articlePritchard A. (2026) · DOI: 10.7748/ns.2026.e12636

- [2]Associations Between Numeracy, Mathematics Anxiety, Perceived Teaching Quality and Medication Calculation Competence Among Undergraduate Nursing Students: A Cross-Sectional Study.Research articleAl-Ghraiybah T, Zahr Z, Chen S, Torrelli C, Pich J, Gholizadeh L. (2026) · DOI: 10.1002/nop2.70679

## 임상 시나리오

Clinical Practice Guide: Subcutaneous Heparin Administration

Independent Double-Check

Heparin is a high-alert medication. Always perform an independent double-check of the dose calculation with another qualified nurse before drawing up and administering the medication. Verify the original order, the calculation, the drawn volume in the syringe, and the patient's identity using two identifiers.

Safe Injection Technique

Administer heparin subcutaneously into the abdomen, ensuring a distance of at least 2 inches from the umbilicus. Rotate injection sites systematically to prevent lipodystrophy and bruising. Do not aspirate after needle insertion, and do not massage the site post-injection, as this can increase the risk of hematoma formation. Apply gentle pressure if needed.

Patient Monitoring and Safety

Monitor the patient for signs of bleeding, such as epistaxis, hematuria, melena, or excessive bruising. Regularly check the platelet count and activated partial thromboplastin time (aPTT) or anti-Xa levels as ordered. Ensure the patient's call light is within reach and educate them to report any unusual bleeding, abdominal pain, or signs of hypersensitivity immediately.

## 핵심 개념

- **Desired Dose (D)** — The amount of medication prescribed by the provider; in this case, 5,000 units of heparin.
- **Available Concentration (H)** — The strength of the medication on hand, expressed as 10,000 units per 1 mL.
- **Volume to Administer (V)** — The calculated amount in mL to be given to the patient, derived from D/H * Quantity.
- **High-Alert Medication** — A drug like heparin that carries a heightened risk of causing significant patient harm when used in error.

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