Fluconazole is a generic prescription drug used to treat certain types of fungal infections. It’s also available as the brand-name drug Diflucan. Fluconazole can cause side effects that range from mild to serious. Examples include headache and diarrhea.

Fluconazole is an antifungal medication used to treat:

Fluconazole may also be used to prevent candidiasis in people going through a bone marrow transplant who receive radiation or chemotherapy treatment. This is to lower their risk of developing a fungal infection.

Fluconazole is available as an oral tablet, liquid, and injection.

Keep reading to learn about the common, mild, and serious side effects that fluconazole can cause. For a general overview of the drug, including details about its uses, see this fluconazole overview article.

Some people may experience mild to serious side effects during their fluconazole treatment. Examples of the drug’s commonly reported side effects include:

  • headache*
  • diarrhea
  • stomach pain
  • dizziness
  • changes in taste

* To learn more about this side effect, see the “Fluconazole’s side effects explained” section.

Mild side effects have been reported with fluconazole. These include:

  • dizziness
  • nausea
  • headache*
  • diarrhea
  • stomach pain
  • changes in taste
  • vomiting

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking fluconazole unless your doctor recommends it.

Fluconazole may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

* To learn more about this side effect, see the “Fluconazole’s side effects explained” section.

Serious side effects have been reported with fluconazole. These include:

If you develop serious side effects while taking fluconazole, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Fluconazole’s side effects explained” section.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with fluconazole, visit MedWatch.

ALLERGIC REACTION

For some people, fluconazole can cause an allergic reaction. Skin rashes, including serious skin reactions, have been reported in studies of people taking fluconazole.

In general, symptoms of allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking fluconazole.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to fluconazole, they may have you switch to a different treatment.

Get answers to some frequently asked questions about fluconazole’s side effects.

Do fluconazole’s side effects differ based on the strength I take (150 mg, 200 mg)?

It’s possible. The side effects you may experience from a fluconazole dose of 200 milligrams (mg) compared with a 150-mg dose may differ. Higher doses of the drug may increase your risk of certain side effects.

This is because, with a higher dose, you have more fluconazole in your body. Your risk of side effects of fluconazole may also be higher if you take a higher dose for a longer period of time.

Talk with your doctor or pharmacist if you have questions about side effects of fluconazole based on the dosage you’ve been prescribed.

How long do fluconazole side effects last?

The common side effects of fluconazole are typically mild and should last only temporarily. However, it’s important to know that various factors could affect how long side effects of fluconazole may last.

These factors include:

  • your dosage
  • how long you take fluconazole
  • your age
  • other health conditions you may have

Although it’s rare, some people may experience side effects of fluconazole that last long term. This was reported in studies of the drug. Long-term side effects include those that may start at any time when you’re taking a drug, even if you’ve taken it for a long time. It also includes side effects that may not go away, even after you stop taking the drug.

Examples of long-term side effects reported in fluconazole’s studies include:

If you have questions about your risk of side effects with fluconazole and how long they may last, talk with your doctor or pharmacist.

Learn more about some of the side effects fluconazole may cause.

Headache

Headache was a common side effect reported in studies of fluconazole. In most cases, this is a mild side effect and should be temporary. However, if you have other symptoms with headache (such as tiredness, fever, or nausea) or if you have a severe headache that doesn’t go away, call your doctor. They can help diagnose the cause of your headache and other symptoms.

What might help

If you experience headache that’s bothersome or doesn’t go away during fluconazole treatment, talk with your doctor. For mild headache, they may recommend treatments such as heat or cold therapy, massage, or nonsteroidal anti-inflammatory drugs such as Advil (ibuprofen) or acetaminophen (Tylenol).

Adrenal insufficiency

Taking fluconazole may cause adrenal insufficiency. This is a rare but serious side effect reported in studies of the drug.

Symptoms may include:

What might help

If you have symptoms of adrenal insufficiency, talk with your doctor. They can diagnose your condition and help determine whether you have adrenal insufficiency. If you do have it, they can help you treat it. In this case, they’ll likely stop treatment with fluconazole and suggest safer options for you to consider.

During your fluconazole treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how fluconazole affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before starting treatment with fluconazole.

Warnings

Fluconazole can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether fluconazole is a good treatment option for you.

Talk with your doctor about your health history before you take fluconazole. Be sure to tell them if any of the following factors apply to you:

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.