What the label lists and what reports show
Dalteparin side effects
Dalteparin's FDA label: “Most common adverse reactions (>1%) are: bleeding (including hemorrhage), thrombocytopenia (Type I), hematoma at the injection site, pain at the injection site, transient elevation of transaminases ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer …” FAERS holds 10,517 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 nausea (707 reports).
- No generic listed
- Boxed warning
Check it at the source: the dalteparin FDA label on DailyMed (effective September 30, 2025, Pfizer Laboratories Div Pfizer Inc); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsMost common adverse reactions (>1%) are: bleeding (including hemorrhage), thrombocytopenia (Type I), hematoma at the injection site, pain at the injection site, transient elevation of transaminases ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc.
Table 11
| Reaction | Number at risk | Patients with Major Bleeding n (%) | Patients with Any Bleeding n (%) | Number at risk | Patients with Major Bleeding n (%) | Patients with Any Bleeding n (%) |
|---|---|---|---|---|---|---|
| Total during study | 338 | 19 (5.6) | 46 (13.6) | 335 | 12 (3.6) | 62 (18.5) |
| Week 1 | 338 | 4 (1.2) | 15 (4.4) | 335 | 4 (1.2) | 12 (3.6) |
| Weeks 2 to 4 | 332 | 9 (2.7) | 17 (5.1) | 321 | 1 (0.3) | 12 (3.7) |
| Weeks 5 to 28 | 297 | 9 (3.0) | 26 (8.8) | 267 | 8 (3) | 40 (15) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described in more detail in other sections of the prescribing information. • Risk of Hemorrhage including Spinal/Epidural Hematomas [see Warnings and Precautions (5.1) ] • Thrombocytopenia [see Warnings and Precautions (5.2) ] • Benzyl Alcohol Preservative Risk to Premature Infants [see Warnings and Precautions (5.3) ] Most common adverse reactions (>1%) are: bleeding (including hemorrhage), thrombocytopenia (Type I), hematoma at the injection site, pain at the injection site, transient elevation of transaminases ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc. at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not accurately reflect the rates observed in practice. Hemorrhage The most commonly reported adverse reactions are hematoma at the injection site and hemorrhagic complications. The risk for bleeding varies with the indication and may increase with higher doses. …
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective September 30, 2025 (SPL set 23527b8b-9b28-4e6d-9751-33b143975ac7), via openFDA; the full label on DailyMed
What do FAERS reports show?
10,517 reports list dalteparin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,287 are coded as a death and 5,467 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 17 reactions below, none is 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?
- Dalteparin: 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