Cefdinir is a safe, FDA-approved antibiotic that has been widely prescribed for decades to treat common bacterial infections in both adults and children as young as 6 months old. Like all antibiotics, it carries some risk of side effects, but most people tolerate it well. The most common complaint is diarrhea, and serious reactions are rare.
What Cefdinir Treats
Cefdinir is a third-generation cephalosporin, part of the same broad family as penicillin-type antibiotics. It works by breaking down bacterial cell walls, killing the bacteria causing your infection. It’s approved for mild to moderate infections including sinus infections, strep throat, tonsillitis, ear infections (in children), community-acquired pneumonia, flare-ups of chronic bronchitis, and uncomplicated skin infections.
It comes in capsules for adults and a liquid suspension for children. Treatment courses typically run 5 to 10 days depending on the type of infection.
Common Side Effects
Diarrhea is the most frequently reported side effect. Other common reactions include nausea, vomiting, stomach pain, and headache. Vaginal yeast infections can also occur because antibiotics disrupt the normal balance of bacteria and yeast in the body. These side effects are generally mild and resolve once you finish the course.
One side effect that catches people off guard: reddish or maroon-colored stools. This is harmless. Cefdinir reacts with iron in your diet or supplements to form a reddish compound in the gut. In one small study of 39 infants and children, about 10% developed red stools while taking cefdinir. The color returns to normal after the medication is stopped, and there are no health consequences. It is not blood.
Serious Reactions to Watch For
Serious side effects are uncommon but worth knowing about. Allergic reactions can include rash, hives, swelling of the face or throat, and difficulty breathing or swallowing. These require immediate medical attention.
A more delayed concern is a gut infection caused by harmful bacteria that overgrow when antibiotics wipe out normal intestinal flora. Signs include watery or bloody diarrhea, stomach cramps, and fever. This can develop during treatment or even two months after finishing the antibiotic. If you notice these symptoms well after your course is done, the connection to the antibiotic may not be obvious, so it’s worth flagging to your provider.
Penicillin Allergy and Cefdinir
If you have a penicillin allergy, cefdinir is still an option in most cases. Third-generation cephalosporins like cefdinir have a cross-reactivity rate of less than 1% with penicillin allergies, according to CDC data. That’s significantly lower than first- and second-generation cephalosporins, which carry a 1% to 8% cross-reactivity risk. However, if you’ve ever had a severe allergic reaction to penicillin (anaphylaxis, throat swelling), your prescriber will weigh the risk more carefully before choosing cefdinir.
Iron and Antacid Interactions
Iron supplements and iron-fortified products interfere with cefdinir absorption, making the antibiotic less effective. If you take iron, separate the doses by at least two hours in either direction. The same applies to antacids containing aluminum or magnesium. This is especially relevant for parents giving a child cefdinir, since many infant formulas are iron-fortified.
Safety in Children
Cefdinir is approved for children 6 months and older. Dosing is based on body weight, with a maximum daily dose of 600 mg. For ear infections, sinus infections, strep throat, and skin infections, children typically receive either a twice-daily or once-daily dose for 5 to 10 days. The liquid suspension makes it easier to measure precise doses for smaller children.
The side effect profile in children mirrors adults: diarrhea and stomach discomfort are the most common issues. The red stool phenomenon is more frequently noticed in young children, likely because iron-fortified formula and cereals are a bigger part of their diet.
Safety During Pregnancy and Breastfeeding
Cefdinir carries an FDA pregnancy category B rating, meaning animal studies showed no harm to the fetus and it’s generally considered a lower-risk option during pregnancy. After a single 600 mg dose, cefdinir was not detectable in human breast milk, which is reassuring for breastfeeding mothers.
Kidney Function and Dose Adjustments
If you have significant kidney problems, cefdinir requires a dose reduction. The threshold is a creatinine clearance below 30 mL/min, at which point the standard dose would build up to higher-than-intended levels in the blood. Adults with reduced kidney function are typically limited to 300 mg once daily instead of the usual dosing schedule. For patients on dialysis, similar adjustments apply. Your prescriber and pharmacist will handle this if your kidney function is known to be impaired.