What the FDA labels say about taking them together
Heparin and warfarin
Heparin's FDA label (Heparin Sodium) of April 30, 2026 names warfarin in its drug interactions section, and warfarin's label names heparin too. The heparin label: “Therefore, when heparin sodium is given with dicumarol or warfarin sodium, a period of at least 5 hours after the last intravenous dose or 24 hours after the last subcutaneous dose should elapse before blood is drawn …”
Check it at the source: the heparin FDA label on DailyMed (effective November 28, 2025, Fresenius Kabi USA, LLC); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the heparin label say about warfarin?
Heparin Sodium label (Fresenius Kabi USA, LLC, April 30, 2026), drug interactionsTherefore, when heparin sodium is given with dicumarol or warfarin sodium, a period of at least 5 hours after the last intravenous dose or 24 hours after the last subcutaneous dose should elapse before blood is drawn, if a valid prothrombin time is to be obtained.
Source: FDA drug label (Heparin Sodium, NDA017029), Fresenius Kabi USA, LLC, effective April 30, 2026 (SPL set 2a173253-dfdc-4d9d-8dee-b9c13e6fa9f5), via openFDA
Source: FDA drug label (Heparin Sodium), Fresenius Kabi USA, LLC, effective November 28, 2025 (SPL set d55b4a63-0c04-4874-b74f-9e9b9e8b008c), via openFDA; the full label on DailyMed
What does the warfarin label say about heparin?
Warfarin label, drug interactionsDrug Class: Anticoagulants; Specific Drugs: argatroban, dabigatran, bivalirudin, desirudin, heparin, lepirudin
Warfarin label, warnings and precautionsConcomitant anticoagulation therapy with heparin for 5 to 7 days during initiation of therapy with warfarin sodium may minimize the incidence of tissue necrosis in these patients.
Source: FDA drug label (Warfarin Sodium), Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Heparin | Warfarin | |
|---|---|---|
| Labeled for | Blood clots (DVT and PE), Atrial fibrillation | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.18 per mL 5,000 unit/mL vial | $0.093 per tablet 2 mg tablet |
| Shortage now | In shortage | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once