Megestrol acetate (Megace)

Megestrol acetate is a type of hormone treatment. It is also called Megace or megestrol. It is a man made version of the hormone progesterone. Progesterone is one of the female hormones but men also produce a small amount of it. 

Megestrol acetate is treatment for breast cancer and womb cancer that has:

  • come back after treatment (recurred or relapsed)
  • spread to other parts of the body (secondary or metastatic cancer)

It is also a treatment for poor appetite. Your doctor might suggest you take it if you have lost weight because of cancer or its treatment.

How does megestrol acetate work?

Megestrol acetate is a man-made version of the hormone progesterone. Progesterone is one of the female hormones, but men also make a small amount of it. 

Hormones are natural substances made by glands in our bodies. They are carried around our body in our bloodstream and act as messengers between one part of our body and another.  

Some cancers use hormones to grow or develop. This means the cancer is hormone sensitive or hormone dependent.

Megestrol acetate can interfere with the hormone balance in the body so that the body makes smaller amounts of the hormones that some cancers depend on to grow. It may also interact with other hormones or have a direct effect on the cancer to stop it growing.

How do you have megestrol acetate?

You have megestrol acetate as a tablet.

You must take tablets according to the instructions your doctor or pharmacist gives you.

You should take the right dose, not more or less.

Talk to your specialist or advice line before you stop taking a cancer drug.

How often do you take megestrol acetate?

You usually take megestrol acetate once a day, at the same time each day. But sometimes the dose is divided up, so that you take the tablets a couple of times a day.

When you start taking it you should take them for at least 2 months. This is to find out if they are working. You can take them for many years. 

What are the side effects of megastrol acetate?

Side effects can vary from person to person. They also depend on what other treatments you're having. 

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better. 

Contact your advice line immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects. But you might have some of them at the same time.

Common side effects

These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:

Increased appetite and weight gain

Feeling hungrier can make it difficult to keep your weight down. Your appetite will go back to normal when you stop the treatment but some people need to diet to lose the extra weight.

Talk to your nurse or your dietitian about how to safely control your weight.

Hot flushes and sweats

We have some tips for coping with hot flushes in women and hot flushes in men. This information also includes some of the possible treatments. Talk to your doctor if your hot flushes are hard to cope with. They might be able to prescribe you some medicines.

Shortness of breath

Megestrol acetate can cause you to be short of breath. Tell your doctor or nurse if it happens. 

Rounded face

You may find that your face becomes more rounded. This is sometimes called a moon face.

Raised blood pressure

Tell your doctor or nurse if you have headaches, nosebleeds, blurred or double vision or shortness of breath. You have your blood pressure checked regularly.

Raised blood sugar level

You have regular blood and urine tests to check this. If you have diabetes you may need to check your blood sugar levels more often than usual. 


Constipation Open a glossary item is easier to sort out if you treat it early. Drink plenty and eat as much fresh fruit and vegetables as you can. Try to take gentle exercise, such as walking. Tell your healthcare team if you think you are constipated. They can give you a laxative if needed.

Blood clots

Blood clots can develop in the deep veins of your body, usually the leg. This is called deep vein thrombosis (DVT). A blood clot can be very serious if it travels to your lungs (pulmonary embolism), although this isn’t common.

Symptoms of a blood clot include:

•    pain, redness and swelling around the area where the clot is and may feel warm to touch
•    breathlessness
•    pain in your chest or upper back – dial 999 if you have chest pain
•    coughing up blood

Tell your doctor immediately or go to A&E if you have any symptoms of a blood clot.

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:

  • feeling or being sick
  • fluid build up causing swelling mainly in the ankles
  • women might have vaginal bleeding such as spotting, heavy or breakthrough bleeding that is not part of your period
  • you might feel tired, weak or lacking energy
  • hair loss or thinning
  • skin rash
  • you might have mood changes if you do talk to your doctor or nurse
  • men might lose the ability to have an erection talk to your doctor they can help
  • you may pass wind (flatulence) more often
  • you might pass urine more often during the day
  • diarrhoea
  • high level of calcium in the blood - you'll have regular blood tests to check this
  • heart changes that might slightly increase your risk of a heart attack - your doctor will check your heart regularly
  • you might get pain in the area of the cancer, when you first start taking megestrol - your doctor or nurse can suggest painkillers to take
  • a weak grip, pain, numbness or tingling in your fingers and thumb (carpal tunnel syndrome)

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Pregnancy and contraception

It is unknown whether treatment may or may not harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment.


Don’t breastfeed during this treatment because the drug may come through into your breast milk.

Lactose intolerance

This drug contains lactose (milk sugar). If you have an intolerance to lactose, contact your doctor before taking this medicine.

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

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