What the label lists and what reports show
Cephalexin side effects
Cephalexin's FDA label: “The most common adverse reactions associated with cephalexin include diarrhea, nausea, vomiting, dyspepsia and abdominal pain.” FAERS holds 21,515 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 chronic kidney disease (2,157 reports).
- Generic listed
Check it at the source: the cephalexin FDA label on DailyMed (effective December 31, 2020, Teva Pharmaceuticals USA, Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions associated with cephalexin include diarrhea, nausea, vomiting, dyspepsia and abdominal pain.
From the label: adverse reactions, continuedThe following serious events are described in greater detail in the Warning and Precautions section: Hypersensitivity reactions [ see Warning and Precautions ( 5.1 ) ] Clostridium difficile -associated diarrhea [ see Warnings and Precautions ( 5.2 ) ] Direct Coombs’ Test Seroconversion [ see Warnings and Precautions ( 5.3 ) ] Seizure Potential [ see Warnings and Precautions ( 5.4 ) ] Effect on Prothrombin Activity [ see Warnings and Precautions ( 5.5 ) ] Development of Drug-Resistant Bacteria [ see Warnings and Precautions ( 5.6 ) ] The most common adverse reactions associated with cephalexin include diarrhea, nausea, vomiting, dyspepsia and abdominal pain. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Teva Pharmaceuticals USA, Inc. at 1-888-838-2872 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 reflect the rates observed in practice. In clinical trials, the most frequent adverse reaction was diarrhea. Nausea and vomiting, dyspepsia, gastritis, and abdominal pain have also occurred. As with penicillins and other cephalosporins, transient hepatitis and cholestatic jaundice have been reported.
Source: FDA drug label, Teva Pharmaceuticals USA, Inc., effective December 31, 2020 (SPL set 19307ff0-71de-477b-965d-ea243e5ede3a), via openFDA; the full label on DailyMed
What do FAERS reports show?
21,515 reports list cephalexin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 1,795 are coded as a death and 7,498 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 21 reactions below, 9 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?
- Cephalexin: 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