Fluoroquinolone Antibiotics: Disabling Side Effects, FDA Warnings, and How to Protect Yourself

Fluoroquinolones, a class of antibiotics that includes ciprofloxacin (Cipro), levofloxacin (Levaquin, now discontinued in the U.S. under that brand), and moxifloxacin (Avelox), have been prescribed hundreds of millions of times for infections ranging from pneumonia to urinary tract infections. They are powerful, convenient, and effective. But over the past two decades, a growing body of evidence has shown that they can cause serious, sometimes permanent side effects affecting tendons, nerves, muscles, the brain, the eyes, and even the aorta.

Some patients have described devastating experiences: tendon ruptures requiring repeated surgeries, nerve pain that never resolved, or a cluster of symptoms that left them unable to work. These stories prompted the FDA to strengthen its warnings several times. This article explains what fluoroquinolones are, what research shows about their risks, when they are and are not appropriate, and how patients can protect themselves.

How dangerous are fluoroquinolone antibiotics like Cipro and Levaquin? They are effective but carry serious, sometimes permanent risks. Studies link them to about 2.5 times higher odds of tendon rupture, plus higher risks of nerve damage, aortic tears, and disabling multi-system reactions. Since 2016 the FDA has advised against using them for minor infections like uncomplicated UTIs when safer options exist. They remain important for some serious infections, but should be used cautiously.

What Are Fluoroquinolone Antibiotics?

Fluoroquinolones are a class of broad-spectrum antibiotics, including ciprofloxacin (Cipro), levofloxacin (Levaquin), and moxifloxacin, used for many infections but now known to carry serious potential side effects. Fluoroquinolones are broad-spectrum antibiotics that kill bacteria by interfering with enzymes needed to copy bacterial DNA. They work against many types of bacteria, are well absorbed when taken by mouth, and penetrate tissues well, which made them popular for a wide range of infections. Common examples include ciprofloxacin, levofloxacin, moxifloxacin, and ofloxacin. They are important for certain serious infections, such as some cases of pneumonia, complicated urinary tract and kidney infections, certain bone and joint infections, anthrax, and plague, and for patients who cannot take other antibiotics. Their broad use for minor infections, however, exposed many people to risks that were not necessary. Fluoroquinolones are not the only products to receive class-wide warnings; gadolinium MRI contrast agents are another example.

Can Fluoroquinolones Cause Tendon Rupture?

Yes. A 2019 meta-analysis found fluoroquinolone use associated with about 2.5 times higher odds of Achilles tendon rupture and nearly 4 times higher odds of tendinitis, which led to an FDA boxed warning. Tendon problems were the first major safety concern. The FDA added a Boxed Warning, its strongest warning, for tendinitis and tendon rupture in 2008. A 2019 systematic review and meta-analysis in the European Journal of Clinical Pharmacology by Carlos Alves and colleagues pooled 15 observational studies and found that fluoroquinolone treatment was associated with about 2.5 times higher odds of Achilles tendon rupture and about 4 times higher odds of Achilles tendinitis, as well as increased risk of tendon disorders overall. Risk is higher in people over 60, those taking corticosteroids, and those with kidney disease or organ transplants. Tendon injury can occur within hours to days of starting treatment and up to several months after stopping.

Do Fluoroquinolones Cause Nerve Damage?

They can. Studies link fluoroquinolones to higher risk of peripheral neuropathy, causing pain, numbness, or weakness, and the FDA warns this nerve damage may sometimes be permanent. Peripheral neuropathy, damage to nerves outside the brain and spinal cord, causes pain, burning, tingling, numbness, or weakness, usually in the hands and feet. In 2013, the FDA required label changes stating that fluoroquinolone-associated neuropathy may be permanent. A 2014 study in Neurology by Mahyar Etminan and colleagues, examining 6,226 cases and 24,904 controls among U.S. men aged 45 to 80, found that current fluoroquinolone users had an 83 percent higher risk of peripheral neuropathy, with the highest risk among new users. A comparison drug not expected to cause neuropathy showed no significant risk, supporting a real association.

Eye Problems

A 2012 study in JAMA by Etminan and colleagues, drawn from nearly one million patients in British Columbia who had visited an ophthalmologist, found that current use of oral fluoroquinolones was associated with a 4.5 times higher rate of retinal detachment. The absolute increase was small, about 4 additional cases per 10,000 person-years, meaning roughly 2,500 people would need to take the drug for one additional retinal detachment. Recent and past use were not associated with higher risk. Later studies produced mixed results, but sudden vision changes such as flashes, floaters, or a curtain over the vision require urgent care.

Can Fluoroquinolones Harm the Aorta?

Research associates fluoroquinolones with a higher risk of aortic aneurysm and dissection (tears in the body’s main artery), prompting FDA warnings against their use in people with or at risk of aortic disease. Because fluoroquinolones can affect collagen, researchers examined risks to the aorta, the body’s main artery. A 2015 study in JAMA Internal Medicine by Chien-Chang Lee and colleagues, using Taiwan’s national insurance database, found that current fluoroquinolone use was associated with 2.4 times the risk of aortic aneurysm or dissection. A 2018 Swedish nationwide cohort study in The BMJ by Björn Pasternak and colleagues compared 360,088 fluoroquinolone treatment episodes with matched amoxicillin episodes and found a 66 percent higher risk of aortic aneurysm or dissection within 60 days, about 82 extra cases per million treatment episodes, driven mainly by aneurysm. In December 2018, the FDA warned against fluoroquinolone use in people with or at risk of aortic aneurysms, such as older adults and people with high blood pressure, certain genetic disorders, or blocked arteries, unless no other options are available.

Disabling Side Effects That Occur Together

The most alarming reports involve people who develop several serious problems at once. After reviewing reports of apparently healthy patients who experienced disabling and potentially permanent side effects involving two or more body systems, the FDA in 2016 updated its Boxed Warning. The FDA’s 2016 safety labeling announcement stated that fluoroquinolones are associated with disabling and potentially permanent side effects of the tendons, muscles, joints, nerves, and central nervous system that can occur together in the same patient, within hours to weeks of starting the drug. The agency identified 178 U.S. patients from 1997 to 2015 who took a fluoroquinolone for sinusitis, bronchitis flare-ups, or uncomplicated urinary tract infections and developed such reactions, many lasting more than a year.

A 2015 case series in BMJ Case Reports by Beatrice Golomb and colleagues at the University of California, San Diego described four previously healthy, employed adults whose symptoms began during fluoroquinolone treatment and progressed after they stopped, evolving into a severe, disabling profile involving tendon problems, muscle weakness, neuropathy, autonomic dysfunction, sleep disorders, cognitive problems, and psychiatric symptoms. The authors proposed that delayed mitochondrial toxicity could explain the pattern. Case series cannot establish how common such reactions are, but they document the experiences that patients and advocacy groups have described.

Mental Health and Blood Sugar Effects

In July 2018, the FDA strengthened warnings about two additional risks. Fluoroquinolones can cause significant drops in blood sugar, which in rare cases led to coma, especially in older adults and people with diabetes taking glucose-lowering medicines. The agency also required warnings about mental health side effects, including disturbances in attention, disorientation, agitation, nervousness, memory problems, and delirium. Seizures and other central nervous system effects were already listed on labels. Patients who experience confusion, mood changes, or symptoms of low blood sugar while taking these drugs should contact a clinician promptly.

Other Risks: C. difficile and Costs

Like other broad-spectrum antibiotics, fluoroquinolones disrupt normal gut bacteria and can lead to Clostridioides difficile infection, which causes severe diarrhea and can be life-threatening, particularly in older and hospitalized patients. A 2019 systematic review in PLOS ONE by Kuula and colleagues in Finland examined health service use and costs from fluoroquinolone-related adverse events, including C. difficile diarrhea, liver injury, and seizures, and found that hospitalization was a major driver of costs. Widespread fluoroquinolone use has also contributed to antibiotic resistance, reducing their effectiveness when they are truly needed.

Who Is Most at Risk From Fluoroquinolones?

Group	Main concern
Adults over 60	Tendon rupture, aortic aneurysm, low blood sugar, confusion
People taking corticosteroids	Much higher risk of tendon injury
Kidney, heart, or lung transplant recipients	Tendon rupture
People with aortic aneurysm, high blood pressure, Marfan or Ehlers-Danlos syndromes	Aortic aneurysm or dissection
People with diabetes	Severe low or high blood sugar
People with myasthenia gravis	Worsening muscle weakness; avoid use
People with prior fluoroquinolone reactions	Recurrence; avoid re-exposure

When Fluoroquinolones Are Appropriate

Higher-risk groups include adults over 60, people taking steroids, those with kidney disease, diabetes, aortic disease, or myasthenia gravis, and anyone who had a previous fluoroquinolone reaction. Despite their risks, fluoroquinolones remain valuable for certain infections. The FDA has stated that for some serious bacterial infections, the benefits outweigh the risks and these drugs should remain available. They may be appropriate for some cases of hospital-acquired or complicated pneumonia, complicated urinary tract and kidney infections, certain intra-abdominal and bone infections, infections caused by bacteria resistant to other antibiotics, and patients with allergies to other options. The key change since 2016 is that they should not be first-line choices for uncomplicated urinary tract infections, acute sinusitis, or acute bronchitis flare-ups when safer alternatives exist. Many sinus and bronchitis cases are caused by viruses and do not need antibiotics at all.

Questions to Ask Before Taking One

If a clinician prescribes a fluoroquinolone, it is reasonable to ask: Is this infection serious enough to need this antibiotic class? Is there a safer alternative that would work? Do I have risk factors, such as age, steroid use, kidney disease, diabetes, or aortic disease, that increase my risk? What symptoms should make me stop the drug and call you? Patients should also tell their clinician about any previous reactions to fluoroquinolones, since repeat exposure can trigger more severe effects.

What to Do If You Develop Symptoms

The FDA advises patients to contact their health care professional immediately if they experience serious side effects such as tendon pain, swelling, or inflammation; tingling, numbness, burning, or weakness in the arms or legs; muscle weakness; confusion or mood changes; or symptoms of low blood sugar. Clinicians should stop the fluoroquinolone and switch to a different antibiotic if one is needed. People with tendon pain should rest the affected area and avoid exercise until evaluated. Sudden severe chest, back, or abdominal pain can signal an aortic emergency and requires calling emergency services. Reporting side effects to the FDA’s MedWatch program helps regulators track safety problems.

Living With Persistent Effects

Some people who experience severe fluoroquinolone reactions report symptoms lasting months or years, including chronic pain, fatigue, neuropathy, and cognitive difficulties. Because these reactions are not well understood, patients often struggle to find clinicians familiar with them. Care typically focuses on managing individual symptoms through physical therapy for tendon and muscle problems, pain management for neuropathy, and support for sleep and mental health. Patient advocacy groups have formed to share experiences and push for research. Researchers continue to investigate mechanisms, including effects on mitochondria and collagen, which may eventually lead to better treatments.

Antibiotic Stewardship

The fluoroquinolone story is an example of why antibiotic stewardship, using antibiotics only when needed and choosing the narrowest effective option, matters. Overuse of broad-spectrum antibiotics exposes patients to unnecessary side effects and accelerates resistance. Following the FDA’s warnings, fluoroquinolone prescribing in the United States declined, though they remain among commonly prescribed antibiotics. Patients can support stewardship by not requesting antibiotics for colds and viral infections, taking antibiotics exactly as prescribed when needed, and asking whether a narrower antibiotic would work.

International Action

Regulators outside the United States have also restricted fluoroquinolones. In 2018, the European Medicines Agency recommended restricting their use, advising that they should not be used for mild or moderate infections unless other antibiotics cannot be used, and suspended some older quinolones. The United Kingdom’s medicines regulator further tightened restrictions in 2024, advising that fluoroquinolones be prescribed only when other recommended antibiotics are inappropriate. These international actions reflect a consistent conclusion that these drugs should be reserved for situations where their benefits clearly outweigh their risks.

A Balanced View

Fluoroquinolones are effective antibiotics that remain important for certain serious infections, and most people who take them do not experience serious harm. However, research has linked them to increased risks of tendon rupture, peripheral neuropathy, retinal detachment, aortic aneurysm, blood sugar disturbances, and mental health effects, and some patients experience disabling, persistent reactions involving several body systems. Regulators in the United States and abroad have responded by restricting their use for minor infections. The best approach is to reserve these drugs for situations where they are truly needed, consider individual risk factors, and stop treatment promptly if warning signs appear.

Practical Takeaways

Ask whether a fluoroquinolone is necessary and whether a safer alternative exists, especially for urinary tract infections, sinusitis, or bronchitis. Tell your clinician if you are over 60, take steroids, have kidney disease, diabetes, aortic disease, or myasthenia gravis, or had a previous reaction. Stop the drug and call your clinician at the first sign of tendon pain, numbness, confusion, or low blood sugar. Seek emergency care for sudden severe chest, back, or abdominal pain. Report side effects to the FDA.

How Fluoroquinolones May Damage Tissues

Researchers have proposed several mechanisms for fluoroquinolone toxicity. In laboratory studies, these drugs can increase enzymes that break down collagen and reduce collagen production in tendon cells, which may explain tendon injuries and effects on the aortic wall. Fluoroquinolones also bind magnesium and other minerals and can affect mitochondria, the energy-producing structures in cells, potentially contributing to nerve and muscle problems. Effects on GABA receptors in the brain may explain seizures and psychiatric symptoms. These mechanisms are still being studied, and why some people experience severe reactions while most do not remains unclear, though genetic factors may play a role.

Common Infections and Safer Choices

For uncomplicated bladder infections in women, guidelines generally recommend other first-line options such as nitrofurantoin or fosfomycin, depending on local resistance patterns and individual factors. Most acute sinus infections and bronchitis are viral and resolve without antibiotics; when bacterial sinusitis needs treatment, amoxicillin-based options are typically preferred. Community-acquired pneumonia in otherwise healthy adults is often treated with other antibiotic classes first. Choosing the right antibiotic depends on the infection, allergies, kidney function, and local resistance, so these decisions should be made with a clinician, but patients can ask whether a non-fluoroquinolone option is appropriate.

Athletes and Active People

Because tendon rupture is a key risk, athletes and physically active people should be particularly cautious. Some clinicians advise avoiding strenuous exercise, especially running and jumping, during fluoroquinolone treatment and for a period afterward. Any new pain in the heel, shoulder, hand, or other tendons should prompt stopping the drug and seeking evaluation. Sports medicine clinicians often ask about recent antibiotic use when evaluating sudden tendon injuries.

Reporting and Patient Advocacy

Patient reports to the FDA’s adverse event reporting system played an important role in identifying the disabling multisystem reactions that led to the 2016 warnings. Advocacy groups formed by affected patients brought attention to the issue through testimony at FDA advisory committee meetings and media coverage. Their efforts illustrate how patient experiences, combined with epidemiological research, can drive regulatory changes. Anyone who experiences a serious side effect from any medicine can report it to the FDA’s MedWatch program.

Looking Ahead

Research continues on why fluoroquinolones cause serious reactions in some people, how to identify those at risk, and how to treat persistent symptoms. Antibiotic development efforts aim to provide alternatives for resistant infections. Meanwhile, the evidence supports a cautious approach: reserving fluoroquinolones for situations where they are clearly needed and ensuring patients understand the warning signs.

Drug Interactions to Know

Fluoroquinolones interact with several common products. Antacids, calcium, iron, zinc, and magnesium supplements, and dairy products can bind the drug in the gut and reduce absorption, so doses should be separated by several hours as directed. Some fluoroquinolones can raise levels of theophylline and caffeine and increase the effects of the blood thinner warfarin. Combining them with corticosteroids increases tendon risk. Certain fluoroquinolones can prolong the QT interval on the heart’s electrical tracing, which may be dangerous for people taking other QT-prolonging drugs or with certain heart conditions. Patients should give clinicians and pharmacists a complete list of medicines and supplements.

Children and Pregnancy

Fluoroquinolones are generally avoided in children because animal studies showed damage to developing cartilage, though they are used for specific serious infections when benefits outweigh risks, such as certain complicated urinary tract infections or anthrax exposure. During pregnancy, other antibiotics are usually preferred when effective options exist. Decisions in these groups require careful weighing of risks and benefits by clinicians.

Understanding Absolute Versus Relative Risk

Headlines about fluoroquinolones often cite relative risks, such as a 4.5 times higher rate of retinal detachment, which can sound frightening. Absolute risks, how many additional people are harmed, are often small: about 4 extra retinal detachments per 10,000 person-years of use, or 82 extra aortic events per million treatment episodes in the Swedish study. These numbers matter when the drug is needed for a serious infection. But for minor infections that could be treated with safer drugs or would resolve without antibiotics, even small risks are not worth taking, which is the reasoning behind the FDA’s 2016 restrictions.

Keeping a Record of Antibiotic Reactions

People who have had a serious reaction to a fluoroquinolone should make sure it is recorded as an adverse reaction or allergy in their medical records and pharmacy profiles, so the drug class is avoided in the future. Keeping a personal list of medications that caused problems, and sharing it with every new clinician, emergency department, and pharmacy, reduces the chance of accidental re-exposure. Some patients wear medical alert jewelry or carry a wallet card. Because fluoroquinolones are sometimes given in hospitals and urgent care settings where records may not be available, telling clinicians directly is the most reliable protection.

Common Myths

“All antibiotics carry the same risks.” Fluoroquinolones have specific risks, including tendon rupture and neuropathy, that other common antibiotics do not.

“Side effects stop when you stop the drug.” Some fluoroquinolone side effects can persist or appear after treatment ends.

“Fluoroquinolones should never be used.” They remain important for certain serious infections when benefits outweigh risks.

“Only older people are affected.” Older adults face higher risk, but disabling reactions have been reported in younger, healthy people.

“A stronger antibiotic is always better.” The narrowest effective antibiotic is usually the best choice.

Key Terms

Fluoroquinolones: A class of broad-spectrum antibiotics including ciprofloxacin, levofloxacin, and moxifloxacin.

Boxed Warning: The FDA’s strongest warning on a drug label.

Peripheral neuropathy: Damage to peripheral nerves causing pain, numbness, or weakness.

Aortic dissection: A tear in the inner layer of the aorta, a medical emergency.

Antibiotic stewardship: Efforts to use antibiotics appropriately to reduce harm and resistance.

The Bottom Line

Fluoroquinolone antibiotics such as ciprofloxacin and levofloxacin are effective but carry serious risks. Studies link them to about 2.5 times higher odds of Achilles tendon rupture, higher risks of peripheral neuropathy, retinal detachment, and aortic aneurysm, and the FDA has documented disabling, potentially permanent reactions affecting tendons, muscles, nerves, and the brain at the same time. Since 2016, the FDA has advised against using them for uncomplicated urinary tract infections, sinusitis, and bronchitis flare-ups when other options exist, and European and British regulators have imposed similar restrictions. These drugs remain important for some serious infections, but patients should ask about alternatives, know their risk factors, and stop treatment and seek care at the first sign of serious side effects.

Frequently Asked Questions

How dangerous are fluoroquinolone antibiotics?

Fluoroquinolones such as Cipro and Levaquin are effective but carry serious risks. Studies link them to about 2.5 times higher odds of Achilles tendon rupture and to higher risks of peripheral neuropathy, aortic tears, severe blood sugar swings, and disabling reactions affecting several body systems at once. Most people are not seriously harmed, but the potential side effects are significant.

Which antibiotics are fluoroquinolones?

The fluoroquinolone class includes ciprofloxacin (Cipro), levofloxacin (Levaquin), moxifloxacin (Avelox), and ofloxacin, among others. They are broad-spectrum antibiotics once prescribed very widely. Because of their serious potential side effects, regulators now recommend reserving them for infections where their benefits clearly outweigh the risks rather than using them routinely.

Should I take a fluoroquinolone for a urinary tract infection?

For an uncomplicated urinary tract infection, usually not. Since 2016 the FDA has advised against using fluoroquinolones for uncomplicated UTIs, sinus infections, and bronchitis flare-ups when safer antibiotics are available, because the risk of disabling side effects can outweigh the benefits for these minor infections. Ask your clinician whether another option is appropriate.

What should I do if I develop side effects while taking one?

Stop activities that stress tendons and contact your clinician immediately if you notice tendon pain or swelling, numbness, tingling, or weakness, confusion or mood changes, or symptoms of low blood sugar. Sudden severe chest, back, or abdominal pain can signal an aortic emergency and requires calling emergency services. Prompt action can prevent lasting harm.

Are fluoroquinolone side effects permanent?

Many resolve after stopping the drug, but some can be long-lasting or permanent, including nerve damage and the disabling multi-system reactions the FDA has described. Tendon ruptures may require surgery and long recovery. This potential for lasting harm is why these antibiotics are now reserved for situations where they are truly needed rather than used for minor infections.

References

1. Alves C, Mendes D, Marques FB. Fluoroquinolones and the risk of tendon injury: a systematic review and meta-analysis. European Journal of Clinical Pharmacology. 2019;75(10):1431–1443. PMID 31270563
2. Etminan M, Brophy JM, Samii A. Oral fluoroquinolone use and risk of peripheral neuropathy: a pharmacoepidemiologic study. Neurology. 2014;83(14):1261–1263. PMID 25150290
3. Etminan M, Forooghian F, Brophy JM, et al. Oral fluoroquinolones and the risk of retinal detachment. JAMA. 2012;307(13):1414–1419. PMID 22474205
4. Lee CC, Lee MT, Chen YS, et al. Risk of Aortic Dissection and Aortic Aneurysm in Patients Taking Oral Fluoroquinolone. JAMA Internal Medicine. 2015;175(11):1839–1847. PMID 26436523
5. Pasternak B, Inghammar M, Svanström H. Fluoroquinolone use and risk of aortic aneurysm and dissection: nationwide cohort study. BMJ. 2018;360:k678. PMID 29519881
6. Golomb BA, Koslik HJ, Redd AJ. Fluoroquinolone-induced serious, persistent, multisymptom adverse effects. BMJ Case Reports. 2015;2015:bcr2015209821. PMID 26438672
7. Kuula LSM, Viljemaa KM, Backman JT, et al. Fluoroquinolone-related adverse events resulting in health service use and costs: A systematic review. PLOS ONE. 2019;14(4):e0216029. PMID 31026286
8. U.S. Food and Drug Administration. FDA approves safety labeling changes for fluoroquinolones. July 26, 2016. fda.gov

Last updated: October 6, 2026