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Megestrol acetate (Megace)

This page tells you about megestrol acetate (Megace) and its possible side effects. There is information about


What megestrol acetate is

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 sex hormones but men also produce a small amount of it.

Megestrol acetate is a treatment for the following cancers which have come back after treatment or have spread from where they started.

  • Breast cancer
  • Womb cancer

Megestrol is also a treatment for poor appetite and your doctor may suggest that you take it if you have lost weight because of cancer or its treatment.

Doctors may also suggest it as a treatment for hot flushes in women due to cancer or its treatment.


How megestrol acetate works

Megestrol 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 you have megestrol

Megestrol comes as tablets. You usually take them once a day, at the same time each day. But sometimes the dose is divided up so that you take them a couple of times a day. Swallow the tablets with a glass of water. Your doctor or pharmacist will tell you how often and when you should take them.

It is very important that you take tablets according to the instructions your doctor or pharmacist gives you. For example, whether you have a full or empty stomach can affect how much of a drug gets into your bloodstream. You should take the right dose, not more or less. And never stop taking a cancer drug without talking to your specialist first.

If you miss a dose and remember within a few hours, you can take it as soon as possible. But if it is almost time for your next dose, miss the forgotten dose and carry on as before. Don't take an extra dose to make up for the one that you missed.

If you accidentally take too many tablets, let your doctor know, or go to your nearest accident and emergency department straight away.

The side effects associated with Megestrol are listed below. To find out about coping with the side effects you can click on the underlined links. Where there is no link you can find information in our cancer drugs side effects section or use the search box at the top of the page.


Common side effects

More than 10 in every 100 people have one or more of these. Remember you may only have one or two of these effects and they may be mild.

  • An increased appetite
  • Weight gain from increased appetite and food intake – watching what you eat and exercising regularly can help to control your weight
  • Hot flushes and sweats
  • A rounded face (sometimes called a moon face)
  • Raised blood pressure 
  • Raised blood sugar levels – you will have regular blood tests to check your sugar levels
  • Constipation – drink plenty of fluids and tell your doctor or nurse if the constipation lasts for more than 3 days
  • Blood clots – contact your doctor or nurse straight away if you suddenly become breathless or have chest pain. Also tell them if you have tenderness or swelling in your leg, or if your leg feels hot and becomes red


Occasional side effects

Between 1 and 10 in every 100 people have one or more of these.

  • Feeling or being sick, especially when you first start taking it
  • Fluid build up, causing ankle and finger swelling
  • Vaginal bleeding that is not part of your period (spotting) or your periods may stop
  • Headaches
  • Tiredness and weakness
  • Hair thinning
  • Skin rashes, which may be itchy
  • Mood changes
  • Loss of ability to have an erection
  • Passing wind (flatulence)
  • Needing to pass urine more often
  • Diarrhoea – drink plenty of fluids if you have this and tell your nurse if it gets severe or lasts for more than 3 days
  • High levels of calcium in your blood – you will have regular blood tests to check your calcium levels
  • Skin rashes that may be itchy
  • Heart changes which can slightly increase your risk of a heart attack – your doctor will check your heart regularly while you are having this  treatment
  • Pain in the area of the cancer, when you first start taking megestrol
  • An allergic reaction – let your doctor or nurse know straight away if you have sudden swelling of the face, lips, or tongue, a skin rash, or difficulty breathing
  • Carpel tunnel syndrome – let your doctor or nurse know if you have any pain, tingling or weakness in your hands

Important points to remember

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)
  • Other drugs you are having

Coping with side effects

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. They can give you advice or reassure you. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Other medicines

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


The drug may come through in the breast milk so don't breastfeed during this treatment or for 2 months afterwards.


Related information


More information about Megace

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 25 February 2015