Megestrol oral tablet is a progestin medication used to help relieve symptoms in people with advanced breast or endometrial (uterine) cancer that can’t be removed or has spread to other parts of the body. It’s a type of palliative treatment, which focuses on improving quality of life rather than curing the cancer. The dose is usually taken by mouth two to four times a day. Side effects include weight gain, increased appetite, and vaginal bleeding.
Palliative treatment for advanced breast or endometrial (uterine) cancers when other treatments aren’t working, surgery isn’t possible, or the cancer has spread
Megestrol oral tablet is a progestin, which is a man-made form of the natural hormone progesterone.
It’s not completely clear how this medication works to treat cancer, but it’s thought it helps by affecting hormone levels in your body.
For endometrial (uterine) cancer, it might lower estrogen levels by blocking signals from the brain. For breast cancer, it might block the effects of estrogen, which some cancer cells need to grow.
Source: DailyMed
Along with their needed effects, progestins used in high doses sometimes cause some unwanted effects such as blood clots, heart attacks, and strokes, or problems of the liver and eyes. Although these effects are rare, some of them can be very serious and cause death. It is not clear if these problems are due to the progestin. They may be caused by the disease or condition for which progestins are being used.
The following side effects may be caused by blood clots. Although not all of these side effects may occur, if they do occur they need immediate medical attention.
Get emergency help immediately if any of the following side effects occur:
Check with your doctor as soon as possible if any of the following side effects occur:
More common
Changes in vaginal bleeding (increased amounts of menstrual bleeding occurring at regular monthly periods, lighter vaginal bleeding between menstrual periods, heavier vaginal bleeding between regular monthly periods, or stopping of menstrual periods)
symptoms of blood sugar problems (dry mouth, frequent urination, loss of appetite, or unusual thirst)
Rare
For megestrol—During chronic treatment
Backache
dizziness
filling or rounding out of the face
irritability
mental depression
nausea or vomiting
unusual decrease in sexual desire or ability in men
unusual tiredness or weakness
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Abdominal pain or cramping
bloating or swelling of ankles or feet
blood pressure increase (mild)
dizziness
drowsiness (progesterone only)
headache (mild)
mood changes
nervousness
pain or irritation at place of injection site
swelling of face, ankles, or feet
unusual or rapid weight gain
Less common
breast pain or tenderness
brown spots on exposed skin, possibly long-lasting
loss or gain of body, facial, or scalp hair
loss of sexual desire
trouble in sleeping
Not all of the side effects listed above have been reported for each of these medicines, but they have been reported for at least one of them. All of the progestins are similar, so any of the above side effects may occur with any of these medicines.
After you stop using this medicine, your body may need time to adjust. The length of time this takes depends on the amount of medicine you were using and how long you used it. During this period of time check with your doctor if you notice the following side effect:
Delayed return to fertility
stopping of menstrual periods
unusual menstrual bleeding (continuing)
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Tablet taken by mouth
Can boost appetite and support weight gain
Helps manage symptoms in advanced breast or endometrial (uterine) cancer
Not a cure
Raises the risk for blood clots
Must take a dose multiple times a day
Megestrol oral tablet comes in 20 mg and 40 mg, so you might need to take more than one tablet to make up each dose.
You might need to take megestrol oral tablet together with other cancer treatments. Follow your oncologist’s instructions on how to take all your medications safely.
Megestrol oral tablet can raise your blood sugar levels. If you have diabetes, check your blood sugar levels regularly. Let your care team know if you feel very thirsty, very hungry, or are urinating more than usual.
Megestrol oral tablet can cause blood clots. Get medical help right away if you have leg or arm pain, swelling, or warmth, or if you have chest pain or trouble breathing.
Since megestrol oral tablet affects your hormone levels, don’t stop taking it suddenly without talking to your oncologist. Stopping too quickly can cause symptoms like dizziness, low energy, or menstrual spotting.
Megestrol oral tablet can cause harm to an unborn baby if taken during pregnancy. If you can get pregnant, use non-hormonal birth control while taking this medication, and talk to your oncologist right away if you become pregnant during treatment.
Megestrol oral tablet can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Megestrol oral tablet can cause blood clots, including deep vein thrombosis (DVT), which is a clot in the leg, and pulmonary embolism (PE), which is a clot in the lungs. Call your prescriber right away if you notice symptoms like leg swelling, chest pain, or trouble breathing.
Megestrol oral tablet can cause harm to an unborn baby if taken during pregnancy. In animal studies, high doses led to developmental changes. To be safe, don’t take this medication if you’re pregnant or planning to become pregnant. If you can become pregnant, use non-hormonal birth control while taking this medication. Tell your oncologist right away if you become pregnant during treatment.
Risk factors: Taking megestrol oral tablet long term | Stress such as trauma, injury, or infection
Taking megestrol oral tablet for a long time can affect your adrenal glands, which help your body handle stress. Some people have developed Cushing's syndrome (too much steroid hormone) or adrenal insufficiency (not enough steroid hormone). This can happen while you're taking the medication or even after stopping. Watch for signs like low blood pressure, nausea, vomiting, dizziness, or weakness, especially if you're sick or having surgery. Tell your prescriber right away if you have any of these symptoms — they might need to do tests or give you another medication to help.
Risk factors: Taking megestrol oral tablet long term
Taking megestrol oral tablet for a long time can raise your blood sugar levels, which can lead to diabetes or make existing diabetes worse. Let your prescriber know if you have a history of high blood sugar or notice symptoms like frequent thirst, frequent urination, excessive hunger, or weakness.
You’ll need to take megestrol oral tablet for at least 2 months to see if it’s helping treat your cancer.
Breast cancer: The typical dose is 40 mg by mouth four times a day.
Endometrial (uterine) cancer: The typical dose ranges from 40 mg to 320 mg by mouth per day, split into divided doses
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using medicines in this class with any of the following medicines is not recommended. Your doctor may decide not to treat you with a medication in this class or change some of the other medicines you take.
Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Palliative treatment for advanced breast or endometrial (uterine) cancers when other treatments aren’t working, surgery isn’t possible, or the cancer has spread
Early-stage HR+ breast cancer after surgery to lower the risk of breast cancer coming back
Ductal carcinoma in situ (DCIS) in females after breast surgery and radiation to lower the risk of breast cancer coming back
Lowering the risk of breast cancer in females who are considered high risk
Early stage HR+ breast cancer in postmenopausal women
Advanced or metastatic HR+ breast cancer in postmenopausal women
Advanced breast cancer in postmenopausal women that's getting worse after treatment with tamoxifen
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Leinung, M. C., et al. (1995). Induction of adrenal suppression by megestrol acetate in patients with AIDS. Annals of Internal Medicine.
National Institute of Diabetes and Digestive and Kidney Diseases. (2018). Symptoms & causes of adrenal insufficiency & Addison's disease.
Roeland, E. J., et al. (2020). Management of cancer cachexia: ASCO guideline. Journal of Clinical Oncology.
Strides Pharma Science Limited. (2025). Megestrol acetate tablet [package insert]. DailyMed.
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