Ciprofloxacin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Ciprofloxacin is a fluoroquinolone antibiotic that kills bacteria causing certain serious infections. You may know it as Cipro. Because of its boxed warnings, MedlinePlus is explicit that for bronchitis, sinus infections, and some urinary tract infections it should be used only when other treatment options are not available.
What does it treat?
Ciprofloxacin treats or prevents specific bacterial infections including pneumonia, gonorrhea, typhoid fever, infectious diarrhea, and infections of the skin, bone, joint, abdomen, and prostate, as well as plague and inhalation anthrax. The label dose for an acute uncomplicated urinary tract infection is 250 mg every 12 hours for 3 days, and most other infections run 7 to 14 days. Antibiotics like ciprofloxacin do nothing for colds, flu, or other viruses.
How do you take it?
The regular tablets and suspension are usually taken twice a day, the extended-release tablets once a day, at the same times each day, with or without food. Swallow tablets whole. Do not take ciprofloxacin with dairy products or calcium-fortified juices alone - a meal that includes them is fine. Antacids with calcium, aluminum, or magnesium, plus iron or zinc supplements, phosphate binders, and sucralfate, block absorption: take ciprofloxacin at least 2 hours before or 6 hours after those. Finish the entire prescription, and if you miss a dose take it when you remember unless the next one is close - never double up. One more rule from MedlinePlus: do not drive or do anything requiring alertness until you know how it affects you.
Side effects to know
- Common: nausea, vomiting, stomach pain, heartburn, diarrhea, vaginal itching or discharge, pale skin, and unusual tiredness or sleepiness.
- Serious: the boxed warnings lead. Tendinitis and tendon rupture can happen during treatment or months later - stop, rest, and call your doctor for tendon pain or swelling, and get emergency care for a snap or pop with inability to bear weight. Nerve damage (numbness, tingling, burning, weakness) may be permanent. Brain and nervous system effects can include seizures, nightmares, hallucinations, confusion, and thoughts of self-harm, sometimes after the first dose. Also watch for severe watery or bloody diarrhea, liver problems (yellowing skin, dark urine), low blood sugar symptoms, and allergic reactions.
Who should not take it?
People with myasthenia gravis should generally avoid it - it can cause severe muscle weakness and breathing difficulty - and anyone taking tizanidine (Zanaflex) should not take ciprofloxacin at all. The tendon risk is highest over age 60, in people taking steroids, and in transplant recipients. It is not normally given to children under 18 because of joint risks, except for specific serious infections or anthrax or plague exposure. Tell your doctor about heart rhythm problems, QT prolongation, an aortic aneurysm, diabetes or low blood sugar, seizures, kidney or liver disease, and if you are pregnant (call your doctor if you become pregnant) or breastfeeding - MedlinePlus says not to breastfeed while taking it and for at least 2 days after the final dose. It also makes skin sun-sensitive: use sunscreen and skip tanning beds.
When is it an emergency?
Call 911 for a tendon snap or pop with inability to move or bear weight, for seizures or fainting, for an allergic reaction with facial or throat swelling or trouble breathing, and for sudden severe pain in the chest, stomach, or back. Stop the medication and call your doctor immediately for numbness or tingling, hallucinations or suicidal thoughts, yellowing skin or eyes, or severe or bloody diarrhea. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why can't I take ciprofloxacin with milk or antacids?
Calcium, aluminum, magnesium, iron, and zinc bind ciprofloxacin in the gut and keep it from being absorbed. MedlinePlus's rule: do not take it with dairy products or calcium-fortified juices alone (a meal containing them is fine), and take ciprofloxacin at least 2 hours before or 6 hours after antacids, iron or zinc supplements, phosphate binders, or sucralfate.
What is the tendon warning about?
Ciprofloxacin carries a boxed warning for tendinitis and tendon rupture, during treatment or up to several months after. The risk is highest over age 60, in people taking steroids, and in transplant patients. Tendon pain, swelling, or stiffness means stop, rest, and call your doctor; a snap or pop with inability to bear weight is an emergency.
Why did my doctor say ciprofloxacin is not a first-choice antibiotic?
For bronchitis, sinus infections, and certain urinary tract infections, MedlinePlus says ciprofloxacin should be used only when other treatment options are not available. The fluoroquinolone class carries boxed warnings for tendons, nerves, and the nervous system, so safer antibiotics get used first when they can do the job.
Can I take ibuprofen while on ciprofloxacin?
Not without asking first. MedlinePlus lists NSAIDs like ibuprofen and naproxen as products that may interact with ciprofloxacin and says not to start them while taking it without discussing with your healthcare provider.
Does ciprofloxacin make you sensitive to the sun?
Yes. MedlinePlus advises avoiding unnecessary or prolonged sun exposure and tanning beds, and wearing protective clothing, sunglasses, and sunscreen. If your skin becomes reddened, swollen, or blistered like a bad sunburn, call your doctor.
Can I drink alcohol while taking ciprofloxacin?
Neither the FDA label nor MedlinePlus lists a specific alcohol interaction for ciprofloxacin. Alcohol can worsen nausea and dizziness while your body fights an infection, so many clinicians suggest skipping it during the course - ask your doctor about your situation.