Heparin
Heparin is an anticoagulant medication that works by enhancing the activity of antithrombin III to inhibit blood clotting factors. It is commonly used to prevent and treat dangerous blood clots in conditions such as deep vein thrombosis, pulmonary embolism, and during certain surgeries or procedures.
A fast-acting anticoagulant that prevents blood clots by enhancing the body's natural inhibitors of the clotting cascade.
Key facts at a glance
- ATC
- B01AB01
- RxNorm
- 5224
- Generic
- Heparin
- Class
- atc-b01
- Brands
- Defencath
- Availability
- rx
- Lactation
- unknown
- Routes
- —
- Forms
- injection, prefilled syringe, solution
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 5000 units
- Maximum
- consult physician
- Frequency
- every 8 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 50-100 units/kg
- Maximum
- consult physician
- Frequency
- every 4 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 5000 units
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
7 groupspregnancy
first trimesteruse lowest effective dose
prefer unfractionated heparin over LMWH in pregnancy due to reversibility; avoid if possible in first trimester unless benefits outweigh risks
regular fetal monitoring and maternal platelet counts
Use with caution and monitor for adverse effects.
pregnancy
second third trimesterstandard dosing
heparin does not cross placenta making it safe for fetus; preferred anticoagulant in pregnancy
monitor maternal platelet counts and aPTT
lactation
breastfeedingno adjustment needed
compatible with breastfeeding; molecular weight prevents significant excretion in breast milk
no specific monitoring required
pediatric_age
neonates infantsweight-based dosing with frequent adjustment
use with extreme caution; dosing differs from adults; require specialized pediatric protocols
frequent aPTT monitoring and platelet counts to monitor for HIT
Use with caution and monitor for adverse effects.
geriatric
elderly over 65consider reduced initial dose and careful titration
increased sensitivity to anticoagulant effects; higher risk of bleeding complications; start with lower doses
frequent monitoring of aPTT and renal function; monitor for signs of bleeding
Use with caution and monitor for adverse effects.
renal_impairment
mild moderateno significant adjustment for unfractionated heparin
unfractionated heparin preferred over LMWH as it is not renally cleared; monitor renal function
monitor renal function and aPTT closely
Use with caution and monitor for adverse effects.
hepatic_impairment
mild moderateuse with caution
altered metabolism may affect anticoagulation; use with careful monitoring
frequent aPTT monitoring and liver function tests
Use with caution and monitor for adverse effects.
Statistics and clinical data
Commonly prescribed since
General prescribing information
Drug class
Drug class information
Common uses
Common therapeutic uses
Mechanism of action
Pharmacological mechanism
Used to prevent and treat deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation with embolism, acute coronary syndrome, and during surgeries such as cardiac catheterization, dialysis, and open-heart surgery. Also used for maintaining catheter patency and preventing clots in hospitalized patients.
Heparin binds to antithrombin III, inducing a conformational change that dramatically increases its ability to inactivate thrombin (Factor IIa) and Factor Xa, as well as other activated coagulation factors. This prevents the conversion of fibrinogen to fibrin, thereby inhibiting clot formation.
Administered by injection (IV or subcutaneous), with dosing based on weight and requiring regular monitoring of aPTT/anti-Xa levels. Major risks include bleeding complications and heparin-induced thrombocytopenia (HIT). Protamine sulfate is the reversal agent. Use cautiously in patients with renal impairment, recent surgery, or history of bleeding disorders.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy