Navigating Cushing’s Syndrome: What to Know About Korlym for High Blood Sugar

Written by Patricia Weiser, PharmD
Medically Reviewed by Michelle Vermeulen, PharmD on October 16, 2025
10 min read

If you have high blood sugar from Cushing’s syndrome, you know how challenging it can be to control. Surgery can sometimes cure the condition, but it is not always successful or possible for everyone. In these cases, a once-daily pill called Korlym (mifepristone) may be an option.

Korlym is FDA-approved to treat high blood sugar (hyperglycemia) in certain people with endogenous Cushing’s syndrome. It’s a disorder where your adrenal glands make too much cortisol, usually because of tumors that affect hormones. Excess cortisol can interfere with metabolism, including how your body regulates blood sugar. 

High cortisol levels can cause or worsen type 2 diabetes or problems with blood sugar (glucose intolerance). People with Cushing’s syndrome often have high blood sugar that is hard to treat, even with diabetes medicines. 

Korlym may also be used for other conditions as determined by your health care provider. This article answers common questions about Korlym for high blood sugar in people with Cushing’s syndrome.

To see if Korlym is right for you, your health care provider may consider factors such as the type of Cushing’s syndrome you have and whether you are able to have surgery to remove the source of excess cortisol. They will also review your lab tests, overall health, and medical history.

Korlym is FDA-approved to control high blood sugar caused by high cortisol levels in adults with endogenous Cushing’s syndrome who also have type 2 diabetes or glucose intolerance and have not improved after surgery or cannot undergo surgery. 

Let’s break down what this means:

  • High cortisol is also called hypercortisolism and happens when there is too much cortisol in your body. Cortisol is a hormone made by the adrenal glands that helps your body respond to stress and regulate blood sugar, among many other body functions. Lab tests are used to measure cortisol levels in your blood, saliva, or urine. 
  • High blood sugar, also called hyperglycemia, happens when there is too much sugar (glucose) in the blood. The sugar in your blood mainly comes from food. Normally, your body releases insulin to move sugar into cells, where it gets used for energy. However, in people with type 2 diabetes or glucose intolerance, this process does not work the way it should, and too much sugar stays in the blood.  
  • Endogenous Cushing’s syndrome happens when the body makes too much cortisol. There are different reasons this can happen, but the most common is a tumor in the pituitary gland (a small gland at the base of the brain) that triggers the adrenal glands to keep making cortisol.

Surgery is a common treatment, because tumor removal can sometimes cure the condition. Korlym is typically prescribed when surgery did not work or if surgery isn’t an option. For example, some people may not be able to have surgery due to health reasons or because the tumor cannot be removed.

Korlym is not FDA-approved to treat people who have type 2 diabetes that is not caused by Cushing’s syndrome. Also, Korlym is not approved for use in children. Talk with your health care provider to see if Korlym is right for you.

Over time, excess cortisol interferes with the body’s ability to use insulin. It can impair how the pancreas releases insulin, the body’s response to insulin, and the action of hormones that help regulate blood sugar. These changes can lead to high blood sugar (hyperglycemia) that is hard to treat.

Korlym helps control blood sugar by blocking the effects of cortisol. It works by blocking the part of a cell that normally responds to cortisol (glucocorticoid receptor). By doing this, Korlym stops the unwanted effects of excess cortisol that lead to high blood sugar. This can help reduce blood sugar in people with Cushing’s syndrome.

Even though Korlym blocks cortisol’s effects, the body continues to make cortisol. In fact, cortisol levels may rise, but its harmful effects on metabolism are reduced.

Korlym is a tablet that you take by mouth once a day with a meal. It comes in one strength of 300 milligrams (mg). 

Your health care provider will tell you how much Korlym to take. Your dosage may vary depending on other medicines you take, other health conditions such as kidney or liver problems, and your body weight. 

The typical starting dosage of Korlym is 300 mg once daily. Your health care provider may slowly increase the dose over time, depending on how your body responds to the medicine. As long as the medicine is well-tolerated, your provider may increase your dose every two to four weeks. If a dose increase is hard to tolerate, your provider may lower it again. The goal is to find the lowest dose that controls your symptoms without causing bothersome side effects. 

The typical maximum dose of Korlym is 1,200 mg, but no more than 20 mg per kilogram (kg) of body weight (1 kg equals 2.2 pounds). If you have kidney or liver problems, your provider may limit your dose to no more than 600 mg.

Note: Even if your prescribed dose is more than one tablet, always take Korlym as a single daily dose with a meal. For example, if your dose is 600 mg, you will take two tablets at one time. (You can swallow them together, or swallow one right after the other.) Swallow each tablet whole. 

It’s important to tell your health care provider before you start any new medicines or supplements while taking Korlym. Many other medicines can interact with Korlym, and some interactions can raise the risk of serious side effects. Depending on the situation, your health care provider may lower your dose of Korlym or stop it completely. Or they may adjust the dose of the new medicine or prescribe an alternative that does not interact.

After you start Korlym, be sure to attend all doctor appointments and lab tests. To see how the medicine is working and to guide dose adjustments, you and your health care provider will monitor your blood sugar levels and symptoms of Cushing’s syndrome. Results can vary, but here’s a general timeline of what to expect during treatment and when:

  • Within the first six weeks of treatment: You may start to notice improved blood sugar readings and mood. During this time, your provider may adjust the dosage of any medicines you take to control your blood sugar. For example, you may not need as much insulin as you did before starting Korlym. 
  • After two months of treatment: You may gradually start to notice improvements in other signs and symptoms of Cushing’s syndrome, such as changes in skin or body weight. Your provider will continue to check your progress regularly and may adjust your dose of Korlym based on how you feel and your blood sugar levels.

Keep in mind that Korlym works by blocking cortisol’s effects (not lowering cortisol levels), so lab results may show high cortisol levels even as your symptoms improve. This is expected and does not mean the medicine is not working.

A 24-week clinical trial was done to study the effect of Korlym on high blood sugar caused by high cortisol in adults with endogenous Cushing’s syndrome. People could join the study if they had high cortisol levels and already tried other treatments (such as surgery) or surgery was not an option for them. People also had to have one of the following problems related to Cushing’s syndrome: type 2 diabetes, problems with blood sugar (glucose intolerance), or high blood pressure. In addition, people had to have at least two symptoms of Cushing’s, such as a rounded face, mood changes, or acne.

Here are some details about the 50 adults who took part in the study:

  • Age: 45 years on average, ranging from 26 to 71
  • Sex: 70% female and 30% male
  • Race: 84% White and 16% Black/African-American
  • Ethnicity: 92% Not Hispanic/Latino and 8% Hispanic/Latino
  • Weight: 220 pounds on average (100 kg)
  • Body Mass Index (BMI): Most people were overweight or obese, with an average BMI of 36

Everyone in the study had endogenous Cushing’s syndrome, meaning their body was making too much cortisol. Specifically, most people (86%) had a tumor in the pituitary gland (Cushing’s disease), some (8%) had a cortisol-triggering tumor outside the pituitary, and the rest (6%) had adrenal cancer.

The researchers divided participants into two groups: 29 people with type 2 diabetes or glucose intolerance (the “diabetes” group, for short) and 21 people with high blood pressure. Everyone took Korlym once daily for up to six months (24 weeks).

People in the diabetes group took oral glucose tolerance tests (OGTTs) to measure blood sugar levels at the start of the study and regularly during treatment. (The OGTT involves drinking a glucose solution, then your blood sugar is measured after two hours.)

The main goal for the diabetes group was to see how many people responded to Korlym treatment. To count as a responder, a person’s blood sugar levels had to drop by at least 25% over time, compared with the start of the study. 

The main results were based on 25 people from the diabetes group who took Korlym for at least 30 days. Of these 25 people, 15 were responders. In other words, 60% had a meaningful improvement in blood sugar control after six months of treatment.

The main goal for the high blood pressure group was to see how many people had their diastolic blood pressure (the bottom number) drop by a certain amount. Of the 21 people in the group, eight people (38%) met this goal. The average blood pressure of the whole group was about the same at the end of the study as it was at the start. 

Overall, this study showed that Korlym can be effective for improving blood sugar control in adults with Cushing’s syndrome and diabetes/glucose intolerance and led to its FDA approval for this purpose. Korlym is not FDA-approved for improving blood pressure. 

Your results may be different from what was seen in the study.

Korlym may cause side effects. Not everyone will have them, and some may be mild, but it is important to know what to watch for. Below are some of the most common side effects and tips to prevent or manage them: 

  • Nausea and vomiting: Nausea is the most common side effect of Korlym. Always take Korlym with a meal. If you feel sick, try eating small, frequent snacks or meals throughout the day, such as crackers or toast. Sip on clear fluids to stay hydrated. Tell your health care provider if nausea or vomiting is severe or does not improve.
  • Fatigue: Korlym may cause tiredness. Try to get enough rest, eat balanced meals, and stay active to help maintain your energy.
  • Headaches or joint pain: If headaches or joint pain are bothersome, an over-the-counter pain reliever may help, but check with a health care professional first. Gentle stretching or light activity can also ease discomfort.
  • Swelling in the hands, legs, or feet: You may have fluid retention while taking Korlym, including ankle or feet swelling. It can help to wear compression socks and stay physically active. 

This is not a complete list of side effects. Talk with your health care provider if you have side effects that bother you. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

Korlym should not be used during pregnancy. Korlym’s active ingredient is mifepristone. Mifepristone blocks the effects of certain hormones, including progesterone, which is needed for keeping a pregnancy. If taken during pregnancy, this medicine can cause loss of the pregnancy (miscarriage). 

If you can become pregnant, your prescriber will talk with you about the importance of pregnancy testing and birth control. For safety reasons, they will make sure you take the following steps:

  • Before starting Korlym, you must take a pregnancy test to confirm you are not pregnant. 
  • If you stop Korlym for two weeks or longer, you must take a pregnancy test to confirm you are not pregnant before restarting it.
  • Hormonal birth control, such as the pill, interacts with Korlym and may not be effective for preventing pregnancy. Instead, use non-hormonal birth control methods, such as condoms, while taking Korlym and for one month after stopping it.
  • If you become pregnant or think you may be pregnant, tell your health care provider right away.

A cost assistance program is available from Corcept, the maker of Korlym. It may reduce the amount you pay. Whether you qualify to enroll may depend on what type of insurance you have or if you are uninsured. Visit the drugmaker’s website for more information about Korlym costs and copay savings. 

You can also contact the drugmaker at 855-767-2273 to connect with a representative for financial support information and other resources.