What volume of heparin (unfractionated heparin) sodium 5000 units/5ml should be administered subcutaneously twice a day for a patient prescribed 5000 units?

Heparin Sodium Dosing Calculation

Administer 5 mL subcutaneously twice daily, as the concentration is 5000 units per 5 mL, which equals exactly 5000 units per dose. 1

Calculation Method

• The concentration provided is 5000 units/5 mL, which simplifies to 1000 units/mL 1
• For a prescribed dose of 5000 units: 5000 units ÷ 1000 units/mL = 5 mL 1
• This volume should be administered via deep subcutaneous (intrafat) injection using a fine needle (25 to 26 gauge) to minimize tissue trauma 1

Administration Guidelines

• Use a different injection site for each administration to prevent the development of massive hematoma 1
• The recommended sites are the arm or abdomen 1
• A concentrated solution of heparin sodium is recommended for subcutaneous prophylactic dosing 1

Dosing Context for VTE Prophylaxis

• The 5000 units BID (twice daily) regimen is the standard prophylactic dose for moderate-risk hospitalized patients 2, 1
• For higher-risk patients (such as those weighing >100 kg, cancer patients, or hip fracture patients), every 8-hour dosing (5000 units three times daily) may be more appropriate 3, 4
• The American College of Cardiology notes that subcutaneous heparin 5000 units twice to three times per day can be considered in patients with renal dysfunction where LMWH is contraindicated 2

Important Clinical Considerations

• Monitoring of aPTT is not routinely required for prophylactic dosing, unlike therapeutic anticoagulation 4
• However, be aware that even prophylactic doses can occasionally prolong aPTT, particularly with higher doses (7500-10,000 units BID) 5
• Periodic platelet counts, hematocrits, and tests for occult blood in stool are recommended during the entire course of heparin therapy 1