What the label lists and what reports show
Mefenamic acid side effects
Mefenamic acid's FDA label: “Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure In patients taking mefenamic acid or other …” FAERS holds 2,183 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 (314 reports).
- Generic listed
- Boxed warning
Check it at the source: the mefenamic acid FDA label on DailyMed (effective April 20, 2026, Lupin Pharmaceuticals, Inc.); 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 mefenamic acid capsules?Mefenamic acid capsules may cause serious side effects, including: S ee "What is the most important information I should know about mefenamic acid capsules, and medicines called nonsteroidal anti-inflammatory drugs (NSAIDs)?" liver problems including liver failure heart failure increase in blood potassium level (hyperkalemia) serious skin reactions, including life-threatening skin reactions new or worse high blood pressure kidney problem including kidney failure life-threatening allergic reactions asthma attacks in people who have asthma low red blood cells (anemia) Other side effects of mefenamic acid capsules include: stomach pain, constipation, diarrhea, indigestion, gas, heartburn, nausea, vomiting, dizziness, swelling, increased liver enzyme levels, headaches, itching, rashes, and ringing in the ear. […]
Source: FDA drug label, Lupin Pharmaceuticals, Inc., effective April 20, 2026 (SPL set d15733a9-d5fd-4d5f-86ce-e7ed8c706c7f), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsBecause some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure In patients taking mefenamic acid or other NSAIDs, the most frequently reported adverse reactions occurring in approximately 1 to10 % of patients are: Gastrointestinal - Abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gross bleeding/perforation, heartburn, nausea, GI ulcers (gastric/duodenal) […]
From the label: adverse reactions, continuedThe following adverse reactions are discussed in greater detail in other sections of the labeling: Cardiovascular Thrombotic Events [see Warnings and Precautions ( 5.1 )] GI Bleeding, Ulceration and Perforation [see Warnings and Precautions ( 5.2 )] Hepatotoxicity [see Warnings and Precautions ( 5.3 )] Hypertension [see Warnings and Precautions ( 5.4 )] Heart Failure and Edema [see Warnings and Precautions ( 5.5 )] Renal Toxicity and Hyperkalemia [see Warnings and Precautions ( 5.6 )] Anaphylactic Reactions [see Warnings and Precautions ( 5.7 )] Serious Skin Reactions [see Warnings and Precautions ( 5.9 , 5.10 )] Hematologic Toxicity [see Warnings and Precautions ( 5.12 )] 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 reflect the rates observed in practice. The following adverse reactions associated with the use of mefenamic acid were identified in clinical studies or post- marketing reports.
Source: FDA drug label, Lupin Pharmaceuticals, Inc., effective April 20, 2026 (SPL set d15733a9-d5fd-4d5f-86ce-e7ed8c706c7f), via openFDA; the full label on DailyMed
What do FAERS reports show?
2,183 reports list mefenamic acid among the medicines taken, each a report of something that happened, not proof the medicine caused it; 107 are coded as a death and 747 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 22 reactions below, 10 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?
- Mefenamic acid: 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