Keflexcephalexin
According to the FDA label: Cephalexin capsules are a cephalosporin antibacterial drug indicated for the treatment of the following infections caused by susceptible isolates of designated bacteria: Respiratory tract infection ( 1.1 ) Otitis media ( 1.2 ) Skin and skin structure infections ( 1.3 ) Bone infections ( 1.4 ) Genitourinary tract infections ( 1.5 ) To reduce the development of drug-resistant bacteria and maintain the effectiveness of cephalexin capsules and other antibacterial drugs, cephalexin capsules should…
21,104 adverse event reports submitted to the FDA (2003–2026)
Top Reported Adverse Events
The most frequently reported events in association with Keflex in the FAERS database. These are events reported by patients taking this medication, not necessarily caused by it. A single report may include multiple events.
Show these terms with plain-language definitions
Tap any term below for a plain-language definition.
Chronic Kidney Disease 2,157 reports
A long-term, gradual loss of kidney function over months or years.
Full definition in the glossary →Renal Failure 1,558 reports
A serious decline in kidney function, where the kidneys can no longer filter waste properly.
Full definition in the glossary →Acute Kidney Injury 1,544 reports
A sudden drop in how well the kidneys are working. It is often temporary and can have many causes.
Full definition in the glossary →Diarrhoea 1,383 reports
Loose or watery bowel movements, often frequent. Also spelled diarrhea in American English.
Full definition in the glossary → See all drugs reporting this event →Pain 1,383 reports
A general report of physical discomfort, used when no more specific location is given.
Full definition in the glossary →Fatigue 1,270 reports
Extreme tiredness or lack of energy that does not improve with rest.
Full definition in the glossary → See all drugs reporting this event →Nausea 1,262 reports
The feeling of sickness in your stomach that often comes before vomiting.
Full definition in the glossary → See all drugs reporting this event →Dyspnoea 1,193 reports
Shortness of breath or difficulty breathing. Also spelled dyspnea in American English.
Full definition in the glossary → See all drugs reporting this event →Anxiety 1,143 reports
A feeling of worry, nervousness, or unease.
Full definition in the glossary → See all drugs reporting this event →Rash 1,128 reports
An area of irritated, red, or bumpy skin.
Full definition in the glossary → See all drugs reporting this event →Headache 1,122 reports
Pain in the head or upper neck.
Full definition in the glossary → See all drugs reporting this event →Drug Ineffective 1,021 reports
A report that the medication did not work as expected for the person taking it. This is a reporting category, not a sign the drug is defective. It simply means someone felt it was not helping their condition.
Full definition in the glossary →Off Label Use 894 reports
Using a medication for a condition or in a way that the FDA has not officially approved. This is common and often legal, and a report of it does not mean something went wrong. Doctors sometimes prescribe drugs off label based on their judgment.
Full definition in the glossary →Vomiting 854 reports
Throwing up the contents of the stomach.
Full definition in the glossary → See all drugs reporting this event →Dizziness 850 reports
A feeling of being lightheaded, unsteady, or like the room is spinning.
Full definition in the glossary → See all drugs reporting this event →
Ranked by frequency of reports, not severity. The most-reported event is not necessarily the most dangerous or the most common in patients taking this drug.
Who Is Reporting
Demographics of patients in FAERS reports that included this information. Not all reports include patient demographics.
By Sex
View reporter sex data as a table
| Sex | Reports |
|---|---|
| Female | 12,749 |
| Male | 7,079 |
| Unknown | 32 |
By Age Group
View age group data as a table
| Age group | Reports |
|---|---|
| 0-17 | 724 |
| 18-34 | 1,482 |
| 35-49 | 2,334 |
| 50-64 | 3,726 |
| 65-74 | 2,888 |
| 75+ | 2,777 |
This shows who filed reports, reflecting who takes this drug and who tends to report, not who is at greatest risk.
Reported Outcomes
Outcomes recorded in FAERS reports that included Keflex. A single report may involve multiple reactions, each with a different outcome. These categories are defined by FDA reporting guidelines, not by PillSignal.
View outcome data as a table
| Outcome | Reports |
|---|---|
| Other Serious | 10,672 |
| Hospitalization | 7,352 |
| Non-Serious | 5,475 |
| Death | 1,769 |
| Life-Threatening | 870 |
| Disability | 710 |
Serious outcomes are far more likely to be reported than mild ones, so this overstates how often outcomes are serious. A recorded death does not mean the drug caused it.
Report Volume Over Time
Number of FAERS reports received per quarter for Keflex. Changes in volume may reflect shifts in prescribing rates, media attention, or reporting behavior, not changes in the medication's safety profile.
View report trend as a table
| Year | Reports |
|---|---|
| 2003 | 1 |
| 2004 | 212 |
| 2005 | 268 |
| 2006 | 321 |
| 2007 | 248 |
| 2008 | 318 |
| 2009 | 387 |
| 2010 | 415 |
| 2011 | 600 |
| 2012 | 699 |
| 2013 | 443 |
| 2014 | 481 |
| 2015 | 835 |
| 2016 | 978 |
| 2017 | 1,176 |
| 2018 | 1,705 |
| 2019 | 2,043 |
| 2020 | 1,529 |
| 2021 | 1,461 |
| 2022 | 1,585 |
| 2023 | 1,624 |
| 2024 | 1,704 |
| 2025 | 1,651 |
| 2026 (partial) | 420 |
The steep increase around 2004 reflects the FDA's move to electronic submission, not a change in this drug's safety. Trends track reporting volume, not risk.
Medications commonly reported with Keflex
In FDA adverse event reports that mention Keflex, these medications appeared most often in the same report.
- Omeprazole (4,079 reports)
- Furosemide (3,551 reports)
- Prednisone (3,531 reports)
- Aspirin (3,419 reports)
- Acetaminophen (3,306 reports)
This reflects co-occurrence in submitted reports, not evidence of drug interaction or combined risk. People often report several medications taken for the same condition or for unrelated reasons. Talk to a doctor or pharmacist about your specific medications.
Related Drugs
Other medications with similar adverse event profiles in FDA FAERS reports.
Data Source
This data is sourced from the FDA's Adverse Event Monitoring System (AEMS), formerly FAERS, via the OpenFDA API. PillSignal is not affiliated with the FDA.
View this data on the FDA website →Data last updated: June 2026