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

Like all antibiotics, Dicloxacillin can cause side effects. Most patients tolerate it well, but knowing what to watch for — and when a symptom means you should stop taking it and call your doctor — is essential for safe treatment.

Common Side Effects of Dicloxacillin (Usually Mild)

The most frequently reported side effects of Dicloxacillin are gastrointestinal. These are generally mild and tend to improve as your body adjusts to the medication:

Diarrhea — One of the most common complaints; usually mild and temporary. Dicloxacillin affects gut flora like all antibiotics.

Nausea — Can occur, especially if Dicloxacillin is taken without adequate water or if you're sensitive to antibiotics.

Skin rash or hives — A mild, non-blistering rash may appear during treatment. Mild rashes don't always indicate allergy, but report them to your provider.

Oral or vaginal candidiasis (yeast infection) — Antibiotics disrupt normal bacterial flora, which can allow yeast to overgrow. This is common with many antibiotics.

Transient elevation in liver enzymes — Often asymptomatic and resolves after stopping the drug. More relevant with long-term use.

Serious Side Effects That Require Prompt Medical Attention

Less commonly, Dicloxacillin can cause more serious reactions. Stop taking the medication and contact your doctor immediately if you experience any of the following:

Severe Allergic Reaction (Anaphylaxis)

Dicloxacillin is a penicillin antibiotic, and people with penicillin allergies may experience serious reactions. Call 911 or seek emergency care immediately if you develop:

Difficulty breathing or wheezing

Swelling of the face, lips, tongue, or throat

Rapid heartbeat or dizziness

A severe, spreading rash with blistering

Liver Damage (Hepatotoxicity)

On rare occasions (estimated incidence of about 1 in 15,000 exposures), Dicloxacillin has been associated with cholestatic jaundice (also called cholestatic hepatitis). This reaction is more common in patients over 55, female patients, and those taking the drug for more than 2 weeks. Importantly, the reaction can occur up to several weeks after stopping the medication and may take weeks to resolve. Call your doctor if you notice:

Yellowing of skin or eyes (jaundice)

Dark-colored urine or pale stools

Severe or persistent abdominal pain

Kidney Damage

Dicloxacillin is primarily cleared by the kidneys, and kidney damage is a rare but recognized adverse effect. Seek care promptly if you notice significantly decreased urination, swelling in the legs or ankles, or extreme fatigue.

Seizures

Rare but reported, especially in patients with kidney disease or those receiving high doses. Stop taking Dicloxacillin and seek emergency care if you experience uncontrolled muscle movements, jerking, or loss of consciousness.

C. diff (Antibiotic-Associated Diarrhea)

Clostridioides difficile (C. diff) can overgrow in the gut when normal bacteria are disrupted by antibiotics. Call your doctor if you experience severe, watery diarrhea with abdominal cramping — especially if it occurs more than 3-4 times per day or if you develop fever.

Tips to Reduce Side Effects

Take on an empty stomach: Dicloxacillin should be taken at least 1 hour before or 2 hours after a meal for best absorption. Eating with it reduces effectiveness.

Drink plenty of water: Take each dose with at least 4 ounces of water and stay upright for 30 minutes after.

Consider a probiotic: Taking a probiotic (e.g., Lactobacillus-based) 2 hours apart from your antibiotic dose may help reduce antibiotic-associated diarrhea. Ask your doctor or pharmacist.

Complete the full course: Even if you feel better after a few days, finish all your Dicloxacillin to prevent antibiotic resistance.

For more information on specific interactions that can increase side effect risk, see our guide to Dicloxacillin drug interactions.