What the label lists and what reports show
Warfarin side effects
Warfarin's FDA label: “Most common adverse reactions to warfarin sodium are fatal and nonfatal hemorrhage from any tissue or organ.” FAERS holds 127,492 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is international normalised ratio increased (10,459 reports).
- Generic listed
- Boxed warning
Check it at the source: the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of warfarin sodium?Warfarin sodium may cause serious side effects, including: See “ What is the most important information I should know about warfarin sodium? ” Death of skin tissue (skin necrosis or gangrene). This can happen soon after starting warfarin sodium. It happens because blood clots form and block blood flow to an area of your body. Call your healthcare provider right away if you have pain, color, or temperature change to any area of your body. You may need medical care right away to prevent death or loss (amputation) of your affected body part. Kidney problems. Kidney injury may happen in people who take warfarin sodium. Tell your healthcare provider right away if you develop blood in your urine. […]
Source: FDA drug label, Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions to warfarin sodium are fatal and nonfatal hemorrhage from any tissue or organ.
From the label: adverse reactions, continuedThe following serious adverse reactions to warfarin sodium are discussed in greater detail in other sections of the labeling: Hemorrhage [see Boxed Warning, Warnings and Precautions (5.1), and Overdosage (10) ] Tissue Necrosis [see Warnings and Precautions (5.2) ] Calciphylaxis [see Warnings and Precautions (5.3) ] Acute Kidney Injury [see Warnings and Precautions (5.4) ] Systemic Atheroemboli and Cholesterol Microemboli [see Warnings and Precautions (5.5) ] Limb Ischemia, Necrosis, and Gangrene in Patients with HIT and HITTS [see Warnings and Precautions (5.6) ] Other Clinical Settings with Increased Risks [see Warnings and Precautions (5.8) ] Other adverse reactions to warfarin sodium include: Immune system disorders: hypersensitivity/allergic reactions (including urticaria and anaphylactic reactions) Vascular disorders: vasculitis Hepatobiliary disorders: hepatitis, elevated liver enzymes. Cholestatic hepatitis has been associated with concomitant administration of warfarin sodium and ticlopidine. …
Source: FDA drug label, Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), via openFDA; the full label on DailyMed
What do FAERS reports show?
127,492 reports list warfarin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 16,218 are coded as a death and 58,202 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 20 reactions below, 6 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Warfarin: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions