Megestrol acetate (Megace®)

Megestrol acetate is a hormonal therapy drug used to treat breast cancer. It is sometimes used to treat womb cancer. Megestrol can also be used to improve your appetite. It’s best to read this information with our general information about the type of cancer you have.

You have megestrol as tablets. Your cancer doctor or nurse will tell you how long you take it for.

Like all hormonal therapy drugs, megestrol can cause side effects. Some of these can be serious so it’s important to read the detailed information below. How hormonal therapy affects people varies from person to person. Your doctor or nurse can talk to you more about this and give you advice on how to manage side effects.

Tell your doctor or nurse straight away if you feel unwell or have severe side effects, including any we don’t mention here. If you need to see a health professional for any reason other than cancer, always tell them that you are having this treatment.

How megestrol works

Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies interfere with the way hormones are made or how they work in the body.

Many cancers need hormones to grow. Megestrol is a drug that is similar to the female sex hormone progesterone. It works by interfering with the hormone balance in the body, which may stop the cancer growing. It can also act directly on cancer cells so that they cannot grow.

When megestrol is given

Megestrol may be used to treat breast cancer which has spread to other parts of the body (secondary breast cancer). It may also be used if breast cancer comes back after treatment.

Megestrol can be used to treat womb cancer which has spread to other parts of the body (advanced) or has come back after treatment.

If you have a poor appetite, your doctor may prescribe megestrol to increase it.

Your doctor or nurse will explain why you are having megestrol and how long you will take it for.

Taking your megestrol tablets

You take megestrol as tablets, usually once a day. Sometimes, your doctor may suggest taking it two or three times a day. Take your tablets with a glass of water at the same time each day. Always take your tablets exactly as your nurse or pharmacist explained. This is important to make sure they work as well as possible for you.

Do not stop taking any of your tablets unless your doctor tells you to. Here are some important things to remember:

  • If you forget to take your tablet, just take your next dose at the usual time. Don’t take a double dose.
  • Keep tablets in their original package at room temperature and away from heat and direct sunlight.
  • Keep them safe and out of the sight and reach of children.
  • Get a new prescription before you run out of tablets and make sure you have plenty for holidays.
  • Return any remaining tablets to the pharmacist if your treatment is stopped.

Possible side effects of megestrol

We explain the most common side effects of megestrol here. We also include some rarer side effects. You may get some of the side effects we mention, but you are very unlikely to get all of them. If you are having other drugs as well, you may have some side effects that we don’t list here.

You will see a doctor or nurse regularly while you have this treatment. Always tell your doctor or nurse about the side effects you have. They can prescribe drugs to help control them and give you advice about managing them. Don’t stop taking megestrol without talking to your doctor first.

More information about this drug

We’re not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium.

Increased appetite

The most common side effect is feeling more hungry than usual. This may cause you to gain weight. This effect on your appetite will go away when you stop taking the drug. If you are worried about gaining weight, talk to your doctor or nurse.

Megestrol is sometimes used to treat people who have lost interest in food and are losing weight. This is because it can help improve appetite.

Swollen hands, feet and ankles

Your hands, feet and ankles may swell because of fluid building up in them. This is not harmful, but can be uncomfortable. Tell your doctor or nurse if you notice any swelling. The swelling will get better after your treatment ends.


You may feel tired and not have much energy while taking megestrol. Pace yourself if you feel tired. Try to balance rest periods with some physical activity such as short walks. This can help you to feel less tired.

Feeling sick

Some people feel sick, especially during the first few weeks of taking megestrol. Tell your doctor if you feel sick. They can prescribe anti-sickness drugs to help.

Mood changes

Megestrol may cause changes to your mood. You may feel anxious or restless. You may also have mood swings or problems sleeping. Tell your doctor or nurse if you have any of these side effects. They can make changes to your treatment if the side effects become a problem.

Skin rashes

Some people experience skin rashes. Tell your doctor if this happens.

Vaginal bleeding in women

Sometimes, women may have light vaginal bleeding (spotting). Let your doctor know if this happens. When you stop taking the drug you may have some bleeding from the vagina, similar to a period.

Less common side effects of megestrol

Tumour flare

If you take megestrol for cancer that has spread to the bones, you may get pain in the bones when you start taking it. This is sometimes called tumour flare. It can also cause high calcium levels in the blood (hypercalcaemia). Your doctor will do regular blood tests to check your calcium levels. 

If your calcium is high, you may feel sick or vomit, be very thirsty, be constipated or, sometimes, feel confused. If you have any of these symptoms, let your doctor know straight away so they can treat it.


If you have diabetes, your blood sugar levels may be higher than usual while taking megestrol. Your doctor will talk to you about how to manage this.

Risk of blood clots

This treatment can increase the risk of getting a blood clot. If you have had a blood clot in the past, you should discuss this with your doctor before taking megestrol.

If you have pain, redness, or swelling in an arm or leg or breathlessness or chest pain, let your doctor know straight away.

Other information about megestrol

Other medicines

Megestrol can affect the way that other drugs work. This includes medicines you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, vitamins and herbal drugs.


It is important to use an effective form of contraception during treatment. Even though women may find that their periods stop while taking megestrol, it is not a contraceptive. Megestrol should not be taken during pregnancy, as it may harm the developing baby.

Medical treatment

If you need to go to hospital for any reason other than cancer, always tell the doctors and nurses that you are taking megestrol. Explain that you are taking hormonal therapy, and that you should not stop or restart it without advice from your cancer doctor. Tell them the name of your cancer doctor so that they can ask for advice.