Heparin Sodium: What It Is and When It's Used

Heparin sodium is a fast-acting anticoagulant (blood thinner) used to prevent and treat blood clots. Hospitals use it for conditions like deep vein thrombosis, pulmonary embolism, during heart procedures, and when people are on dialysis. It doesn’t dissolve clots — it helps stop them from getting bigger while the body breaks them down on its own.

Forms and How It’s Given

Heparin comes in two main forms. Unfractionated heparin (UFH) is usually given through an IV or as repeated subcutaneous injections and is closely monitored in the hospital. Low-molecular-weight heparin (LMWH) is given as a single daily or twice-daily injection under the skin and is often used for outpatient treatment. LMWH is easier to manage at home because it needs less frequent lab checks. You might see heparin in prefilled syringes, vials for IV pumps, or as part of flush solutions to keep IV lines open.

Which type you get depends on the reason for treatment, kidney function, body weight, and bleeding risk. If you’re switching from heparin to an oral anticoagulant or vice versa, your care team will time doses and tests so clotting stays controlled.

Safety: Monitoring, Side Effects and What to Watch For

With UFH, hospitals commonly check aPTT (a clotting test) to keep dosing safe. For LMWH, doctors may check anti-Xa levels in specific situations like pregnancy or kidney disease. The main risk with heparin is bleeding — from small bruises to more serious internal bleeding. Watch for unusual bruising, a nosebleed that won’t stop, bloody urine or stools, heavy menstrual bleeding, sudden severe headache, or weakness. Those need immediate medical attention.

Heparin-induced thrombocytopenia (HIT) is a less common but serious reaction where platelet counts drop and clot risk paradoxically rises. If platelets drop or you see new clots while on heparin, your team will evaluate for HIT and switch medications if needed.

Heparin interacts with other drugs that affect clotting. Take extra care if you use aspirin, NSAIDs, certain antidepressants, or other blood thinners — these increase bleeding risk. Tell every provider and the pharmacist about heparin so they can check for interactions.

Practical tips: store injections as the label directs, never reuse needles, and keep a list of your medications and any recent lab results. Don’t stop heparin suddenly without talking to your doctor — stopping can raise clot risk. If you have surgery or a dental procedure coming up, tell the surgeon and dentist that you’re on heparin so they can plan timing and pauses safely.

Questions about dosing, side effects, or lab tests are normal. Ask your nurse or pharmacist to show you injection technique and explain the monitoring plan. If you notice any signs of bleeding or sudden changes in health, get medical help right away.