Cefaclor Side Effects: What You Need to Know Before Taking It

When you take cefaclor, a second-generation cephalosporin antibiotic used to treat bacterial infections like ear infections, bronchitis, and urinary tract infections. Also known as Cefaclor CD, it works by stopping bacteria from building cell walls, which kills them or stops them from spreading. But like all antibiotics, it doesn’t just target bad bacteria — it can upset your gut, trigger allergic reactions, or cause other side effects you might not expect.

Many people take cefaclor without issues, but diarrhea, a common side effect caused by disruption of gut bacteria happens in up to 1 in 10 users. It’s usually mild, but if it turns watery, bloody, or lasts more than a couple days, it could be Clostridioides difficile, a dangerous infection triggered by antibiotic use. That’s not rare — studies show up to 3% of people on cephalosporins like cefaclor develop this. If you get fever, stomach cramps, or pus in stool, stop taking it and call your doctor immediately.

Another big concern is allergic reactions, especially if you’re allergic to penicillin or other beta-lactam antibiotics. About 5–10% of people with penicillin allergies also react to cefaclor. Symptoms can be mild — rash, itching, hives — or life-threatening: swelling of the face or throat, trouble breathing, or low blood pressure. If you’ve ever had a severe reaction to any antibiotic, don’t take cefaclor without talking to your doctor first.

Less common but still important side effects include nausea, vomiting, headaches, and dizziness. Some people report a metallic taste or darkened tongue — odd, but harmless and temporary. Rarely, cefaclor can affect liver function or cause low white blood cell counts, which makes you more prone to infections. That’s why your doctor might check your blood if you’re on it for more than a week.

Who’s most at risk? Kids, older adults, and people with kidney problems need lower doses. Pregnant women can usually take it safely, but always check with your OB-GYN. And never share your cefaclor with someone else — even if their symptoms sound the same. What works for you might cause serious harm to them.

What you’ll find below are real patient experiences and doctor-approved insights on managing cefaclor side effects. You’ll see how people handled diarrhea without stopping treatment, what to do if you develop a rash, and when to push back if your doctor pushes you to keep taking it. We’ve pulled from posts that compare cefaclor to other antibiotics, explain how to avoid drug interactions, and show how to track your symptoms to spot trouble early. This isn’t just a list of side effects — it’s a practical guide to staying safe while your body fights infection.