Heparin (Low Molecular Weight) — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Heparin (Low Molecular Weight)?
Low molecular weight heparins (LMWH — including enoxaparin, dalteparin) are injectable anticoagulants used for treatment and prevention of blood clots. This medication is funded by Pharmac for VTE treatment and thromboprophylaxis.
What is Heparin (Low Molecular Weight) Used For?
LMWH is used for treatment and prevention of DVT and PE, anticoagulation in acute coronary syndrome, thromboprophylaxis after surgery, and anticoagulation during pregnancy (preferred over warfarin/DOACs).
How Does Heparin (Low Molecular Weight) Work?
LMWHs are derived from standard unfractionated heparin by chemical or enzymatic depolymerisation. They inhibit factor Xa (and to a lesser extent thrombin/IIa) by binding to antithrombin III, enhancing its inhibitory activity. The predominant anti-Xa activity provides predictable anticoagulation with once or twice-daily dosing without the need for routine monitoring in most patients.
How to Take Heparin (Low Molecular Weight)
Administered by subcutaneous injection, usually in the abdomen. Dosing depends on indication, weight, and renal function. For DVT/PE treatment: enoxaparin 1 mg/kg twice daily (or 1.5 mg/kg once daily). For thromboprophylaxis post-surgery: 40 mg once daily. Inject into alternating sides of abdomen, 5 cm from navel.
Common Side Effects of Heparin (Low Molecular Weight)
- Bruising at injection site
- Pain or skin reaction at injection site
- Mild elevation in liver enzymes
- Mild thrombocytopaenia (transient)
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Major bleeding (intra-abdominal, intracranial)
- Heparin-induced thrombocytopenia (HIT) — rare but serious — paradoxical thrombosis with falling platelet count — urgent specialist assessment
- Hyperkalaemia (LMWHs inhibit aldosterone)
- Osteoporosis (with prolonged use during pregnancy)
Drug Interactions
Heparin (Low Molecular Weight) may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Other anticoagulants and antiplatelets (significantly increased bleeding risk)
- NSAIDs (increased bleeding risk)
New Zealand Prescribing Information
Enoxaparin (Clexane® 20 mg, 40 mg, 60 mg, 80 mg, 100 mg prefilled syringes) and dalteparin (Fragmin® 2500, 5000, 7500, 10000 IU syringes) are funded by Pharmac. Routine anti-Xa monitoring is not required for most patients but is recommended in renal impairment (eGFR <30), extremes of body weight, pregnancy, and HIT assessment. LMWH is the anticoagulant of choice in pregnancy as it does not cross the placenta.
Frequently Asked Questions
Do I need blood tests to monitor LMWH injections?
Routine monitoring is not required for most patients on standard-dose LMWH. However, anti-Xa levels may be measured in renal impairment, very low or high body weight, or pregnancy. Your doctor will advise if monitoring is appropriate for you.
How do I give myself a LMWH injection at home?
Inject into the fatty tissue of the abdomen, at least 5 cm from the navel. Pinch a fold of skin, insert the needle at 90 degrees, and inject slowly. Rotate sites. Do not rub the area after injection. Your district nurse or pharmacist will provide training and written instructions.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: