What is the recommended dose of Unfractionated Heparin (UFH) for Deep Vein Thrombosis (DVT) prophylaxis?

UFH Dosing for DVT Prophylaxis

The recommended dose of unfractionated heparin (UFH) for DVT prophylaxis is 5000 IU subcutaneously every 8 hours, which is more effective than twice-daily dosing and represents the standard of care across multiple guidelines. 1, 2

Standard Prophylactic Dosing

UFH 5000 IU subcutaneously every 8 hours is the preferred regimen for DVT prophylaxis in most clinical settings, particularly in:

• General surgery patients - where three times daily dosing was shown to be more effective than twice-daily administration in preventing DVT 1
• Cancer patients - where this is the specifically recommended regimen by the National Comprehensive Cancer Network 1, 2
• ICU patients - when LMWH is contraindicated or unavailable 3

The three times daily dosing provides more consistent anticoagulant effect compared to twice daily dosing and reduced DVT incidence from 29% to 13% in ICU patients. 3, 4

Alternative Dosing: Twice Daily Administration

UFH 5000 IU subcutaneously every 12 hours (twice daily) is an acceptable alternative in general medical patients, though with important caveats:

• A meta-analysis in general medical patients showed no difference in overall VTE rates between twice-daily versus three times daily dosing 1
• However, twice-daily dosing showed less reduction in the combined endpoint of proximal DVT and PE (p=0.05) 1
• The risk of major bleeding was significantly higher with three times daily dosing (p<0.001), which may favor twice-daily dosing in medical patients at higher bleeding risk 1

The FDA label supports both regimens: 5000 units every 8 hours or 8,000-10,000 units every 12 hours for prophylaxis. 5

Special Population Adjustments

Renal Impairment

UFH is the agent of choice for patients with creatinine clearance <30 mL/min because it is primarily metabolized by the liver rather than renally excreted. 1, 2, 3 Standard dosing of 5000 IU every 8 hours can be used without dose adjustment in renal failure. 2, 3

Obesity

For patients weighing >100 kg or BMI >30 kg/m², do NOT increase UFH prophylactic doses above 5000 IU every 8 hours. 6 A study of 1335 overweight and obese patients found that high-dose UFH (7500 units every 8 hours) provided no additional efficacy in reducing VTE but significantly increased bleeding complications, particularly in obese class II and III patients. 6

Cancer Patients

UFH 5000 IU subcutaneously every 8 hours is the specifically recommended regimen for VTE prophylaxis in cancer patients per NCCN guidelines. 1, 2 This population benefits from the more frequent dosing interval.

Duration of Prophylaxis

• Medical patients: Continue until fully ambulatory or hospital discharge 2
• Surgical patients: Minimum 7-10 days or until fully ambulatory, whichever is longer 2, 5
• Cancer patients: Consider extended prophylaxis with ongoing risk factors 2

Critical Timing Considerations

Administer the first dose 2 hours before surgery for surgical prophylaxis, using a fine needle (25-26 gauge) via deep subcutaneous injection in the arm or abdomen to minimize tissue trauma. 5 The most widely used surgical dosage is 5000 units 2 hours before surgery and 5000 units every 8-12 hours thereafter. 5

Common Pitfalls to Avoid

• Do not use UFH in patients with active or history of heparin-induced thrombocytopenia (HIT) - use a direct thrombin inhibitor or fondaparinux instead 1
• Monitor platelet counts every 2-3 days from day 4 to day 14 in patients with HIT risk ≥1% 1
• Avoid administering anticoagulants too close to neuraxial anesthesia due to spinal hematoma risk 2
• Do not routinely monitor anti-Xa levels for prophylactic dosing - this is unnecessary for standard prophylaxis 2, 3
• Do not escalate doses in obese patients - this increases bleeding without improving efficacy 6

When to Choose UFH Over LMWH

UFH should be preferentially selected over LMWH in:

• Severe renal impairment (CrCl <30 mL/min) 1, 2, 3
• Patients without reliable IV access who cannot receive monitored therapeutic anticoagulation 1
• Settings where rapid reversibility is needed (though this is less relevant for prophylactic dosing)
• Cost-sensitive situations where LMWH is not affordable 7

Note that LMWH is generally preferred over UFH when renal function is normal due to more predictable pharmacokinetics, reduced healthcare worker exposure, and lower rates of missed doses. 1, 3