What the label lists and what reports show
Leucovorin side effects
Leucovorin's FDA label lists its adverse reactions in its own words. FAERS holds 19,004 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 diarrhoea (1,800 reports).
- Generic listed
Check it at the source: the leucovorin FDA label on DailyMed (effective March 19, 2025, Meitheal Pharmaceuticals Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsAllergic sensitization, including anaphylactoid reactions and urticaria, has been reported following administration of both oral and parenteral leucovorin calcium. No other adverse reactions have been attributed to the use of leucovorin calcium per se. The following table summarizes significant adverse events occurring in 316 patients treated with the leucovorin calcium/5-fluorouracil combinations compared against 70 patients treated with 5-fluorouracil alone for advanced colorectal carcinoma. These data are taken from the Mayo/NCCTG large multicenter prospective trial evaluating the efficacy and safety of the combination regimen.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| Reaction | Any (%) | Grade3+ (%) | Any (%) | Grade 3+ (%) | Any (%) | Grade 3+ (%) |
|---|---|---|---|---|---|---|
| Leukopenia | 69 | 14 | 83 | 23 | 93 | 48 |
| Thrombocytopenia | 8 | 2 | 8 | 1 | 18 | 3 |
| Infection | 8 | 1 | 3 | 1 | 7 | 2 |
| Nausea | 74 | 10 | 80 | 9 | 60 | 6 |
| Vomiting | 46 | 8 | 44 | 9 | 40 | 7 |
| Diarrhea | 66 | 18 | 67 | 14 | 43 | 11 |
| Stomatitis | 75 | 27 | 84 | 29 | 59 | 16 |
| Constipation | 3 | 0 | 4 | 0 | 1 | - |
| Lethargy/Malaise/Fatigue | 13 | 3 | 12 | 2 | 6 | 3 |
| Alopecia | 42 | 5 | 43 | 6 | 37 | 7 |
| Dermatitis | 21 | 2 | 25 | 1 | 13 | - |
| Anorexia | 14 | 1 | 22 | 4 | 14 | - |
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.
Source: FDA drug label, Meitheal Pharmaceuticals Inc., effective March 19, 2025 (SPL set 9df20901-6980-4d4e-89ec-40f3c1f91852), via openFDA; the full label on DailyMed
What do FAERS reports show?
19,004 reports list leucovorin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,533 are coded as a death and 9,242 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. Reports rose sharply in 2025 (1,956, against a median of 498 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 22 reactions below, 5 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?
- Leucovorin: 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