Levofloxacin Side Effects: What to Expect and When to Call Your Doctor

Levofloxacin is an effective antibiotic, but it carries one of the most extensive safety profiles of any commonly prescribed medication. The FDA has issued boxed warnings — the most serious warning category available — for this drug. Understanding what to expect, and knowing the warning signs that require immediate action, is critical for anyone taking levofloxacin.

This guide covers common side effects, serious side effects, FDA boxed warnings, and clear guidance on when to call your doctor or seek emergency care.

Common Side Effects of Levofloxacin

Most people who take levofloxacin experience one or more of these common, generally mild side effects:

• Nausea (most common — take with food if troublesome)
• Headache
• Diarrhea
• Insomnia or trouble sleeping
• Dizziness
• Constipation or abdominal pain
• Photosensitivity (skin becomes more sensitive to sunlight — use sunscreen and avoid tanning beds)

These side effects are typically manageable and should not cause you to stop taking the medication unless they are severe. If nausea is a problem, taking levofloxacin tablets with food (though not required) may help.

FDA Boxed Warnings: Serious Side Effects That Require Stopping the Drug

Levofloxacin and all fluoroquinolone antibiotics carry FDA boxed warnings — the most serious category of drug warning. If you experience any of the following, stop taking levofloxacin immediately and contact your doctor or seek emergency care:

• Tendinitis and tendon rupture: Pain, swelling, or rupture of tendons, especially the Achilles tendon (the tendon above your heel). Risk is highest in patients over 60, those taking corticosteroids, and organ transplant recipients. Stop levofloxacin immediately if you develop tendon pain and rest the affected area.
• Peripheral neuropathy: Numbness, tingling, burning pain, weakness, or sensory changes in the arms, hands, legs, or feet. This can be irreversible — stopping the drug quickly is essential.
• Central nervous system effects: Seizures, increased intracranial pressure, tremors, agitation, confusion, paranoia, hallucinations, depression, or suicidal thoughts. These psychiatric side effects can occur even in patients with no prior mental health history.
• Exacerbation of myasthenia gravis: Worsening of muscle weakness in patients with myasthenia gravis. Levofloxacin should generally be avoided in patients with this condition.
• Aortic aneurysm and dissection risk: Fluoroquinolones have been associated with an increased risk of aortic aneurysm rupture or dissection. Patients at risk (e.g., elderly, hypertensive, known aortic disease) should discuss this with their doctor.

Other Serious Side Effects to Watch For

• QT prolongation: Levofloxacin can lengthen the heart's QT interval, which can lead to dangerous arrhythmias. Risk is higher if you have low potassium or magnesium, already have a prolonged QT, or are taking other QT-prolonging drugs. Symptoms: palpitations, irregular heartbeat, fainting.
• Blood sugar changes (dysglycemia): Levofloxacin can cause both low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia). This is particularly dangerous in diabetic patients on insulin or oral hypoglycemics. Symptoms of hypoglycemia: confusion, sweating, shakiness, fast heartbeat.
• C. difficile-associated diarrhea (CDAD): Like all antibiotics, levofloxacin can disrupt normal gut bacteria and allow C. difficile to overgrow. Watery or bloody diarrhea during or after treatment may be a sign. Call your doctor before taking anti-diarrhea medication.
• Liver problems: Upper stomach pain, loss of appetite, dark urine, yellowing of skin or eyes (jaundice). Seek medical help immediately.
• Severe allergic reactions: Hives, difficulty breathing, swelling of the face, throat, or tongue. Call 911 or go to the ER immediately.

Who Is at Highest Risk for Serious Side Effects?

Certain patients are at higher risk and should discuss the risk-benefit ratio carefully with their doctor:

• Patients over age 60 (higher tendon rupture risk)
• Patients on corticosteroids (prednisone, etc.) — dramatically increases tendon risk
• Kidney, heart, or lung transplant recipients
• Patients with diabetes (blood sugar fluctuations)
• Patients with epilepsy or history of seizures
• Patients with known QT prolongation or taking QT-prolonging drugs

Practical Safety Tips While Taking Levofloxacin

• Stay hydrated — drink plenty of water to prevent crystalluria (crystals in urine)
• Avoid exercise and strenuous activity during treatment — tendons are vulnerable
• Wear sunscreen and protective clothing outdoors — photosensitivity is real
• Do not drive or operate machinery until you know how levofloxacin affects you — dizziness and CNS effects can impair reactions
• Monitor blood sugar closely if you are diabetic and on insulin or oral medications

Also review our guide on levofloxacin drug interactions to make sure you're not taking any medications that could increase your risk of serious side effects.