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

Diflucan (fluconazole) is generally well-tolerated, especially for the single 150 mg dose most people take for a vaginal yeast infection. Most people experience little to no side effects. But like all medications, fluconazole can cause unwanted effects — and a small number of patients experience serious reactions that require medical attention. This guide walks you through what to expect.

Most Common Side Effects of Diflucan

The following side effects occur in a small percentage of patients — most commonly with higher doses or longer treatment courses. A single 150 mg dose typically causes fewer issues:

Nausea: The most commonly reported side effect. Usually mild and resolves on its own. Taking fluconazole with food may help, though it is not required for absorption.

Headache: Mild to moderate headache is reported in some patients, particularly with multi-day courses.

Abdominal pain or stomach upset: Mild cramping or discomfort in the stomach can occur.

Diarrhea: Loose stools or diarrhea can occur, especially during longer treatment courses.

Dizziness: Some patients report mild dizziness. Avoid driving or operating heavy machinery until you know how fluconazole affects you.

Taste changes: A metallic or altered taste in the mouth is occasionally reported.

Rash: A mild rash occurs in a small percentage of patients. This is usually not serious in otherwise healthy people with superficial infections, but requires monitoring. Contact your doctor if a rash develops.

Serious Side Effects: Call Your Doctor Immediately

Serious side effects from fluconazole are rare, especially with a single dose, but they do occur. Seek immediate medical attention if you experience any of the following:

Severe skin reactions: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but life-threatening skin reactions characterized by blistering, skin peeling, and widespread rash. If you develop a spreading rash with blisters or skin peeling, go to the emergency room immediately.

Liver injury (hepatotoxicity): Fluconazole has been associated with rare but serious cases of liver damage, including fatalities — primarily in patients with serious underlying conditions. Signs include severe nausea, vomiting, dark urine, yellowing of skin or eyes (jaundice), and right upper abdominal pain.

QT prolongation / irregular heartbeat: Fluconazole can prolong the QT interval, a measure of the heart's electrical cycle. This is most concerning at higher doses and when combined with other QT-prolonging drugs. Symptoms include palpitations, rapid or irregular heartbeat, or fainting.

Anaphylaxis: Severe allergic reactions (difficulty breathing, swelling of face, lips, or throat, rapid heartbeat) are rare but require emergency care.

Diflucan and Pregnancy: An Important Warning

High-dose fluconazole (400–800 mg/day) taken during the first trimester of pregnancy has been associated with a pattern of congenital abnormalities in infants. Case reports describe skeletal abnormalities and other defects in infants exposed to these high doses in utero.

The FDA labeling notes a potential risk of spontaneous abortion and congenital abnormalities. If you are pregnant or may be pregnant, talk to your doctor before taking any dose of fluconazole. The single 150 mg dose for vaginal candidiasis has a different risk profile than high-dose multi-day therapy, but all use during pregnancy should be discussed with a healthcare provider.

Side Effects with Higher Doses

The likelihood and severity of side effects increases with dose and duration. Patients taking fluconazole for serious systemic infections at doses of 400–800 mg/day for extended periods face greater risks of hepatotoxicity, QT prolongation, and skin reactions than someone taking a single 150 mg dose for a yeast infection. Your doctor should be monitoring liver function and kidney function for longer-term regimens.

What to Tell Your Doctor Before Taking Diflucan

Before taking fluconazole, inform your healthcare provider if you have or have had:

Liver disease or abnormal liver function tests

Kidney disease (dose adjustment may be needed)

Heart disease, irregular heartbeat, or QT prolongation

Allergy to azole antifungals (ketoconazole, itraconazole, voriconazole)

Current use of warfarin, erythromycin, pimozide, quinidine, amiodarone, clopidogrel, tacrolimus, cyclosporine, or sulfonylureas

Pregnancy or plans to become pregnant

Summary: When to Contact Your Doctor

Call your doctor if you experience: significant nausea or vomiting, yellowing of skin or eyes, dark urine, a developing rash (especially if spreading), heart palpitations, or any reaction that seems unusual. Go to the emergency room immediately for: skin blistering or peeling, severe difficulty breathing, chest pain, or loss of consciousness.

For detailed interaction information, see our guide to Diflucan drug interactions. And if you need help finding Diflucan in stock near you, visit medfinder.com.