Breast screening (mammogram)

This information is about having breast screening. The test is called a mammogram and involves having specialised X-ray pictures taken of each breast. These pictures show small details of the breast tissue that cannot be seen in any other way.

A specialist called a mammographer does your procedure in our breast imaging unit. The mammographer is a female radiographer (health professional who takes X-rays) or specially trained assistant practitioner.

The aim of this information is to help answer some of your questions about having a mammogram. It explains:

If you have any more questions or concerns, please speak to a mammographer in the breast imaging unit or a breast care nurse.

Benefits of a mammogram

A mammogram can detect changes in your breasts. You may be aware of some of these changes, such as a breast lump. 

The mammogram may also show changes that we cannot feel when examining you. This includes small changes within your breasts that we may need to investigate in more detail.

If we can diagnose breast cancer at an early stage, this can lead to higher success rates in treatment.

Specialists called radiologists (doctors who read X-rays) and specially trained mammographers review your mammogram. They interpret the results of your test.

Risks of a mammogram

During a mammogram, you are exposed to X-rays. They are a type of radiation called ionising radiation. This may cause cancer many years or decades after you are exposed to it.

The amount (dose) of radiation used in medical X-rays is very small. This means that the health risks are very low. 

According to scientists, there is less than a 1 in 25,000 risk of the radiation from a mammogram causing breast cancer. The radiation is similar in strength to other types of natural radiation that you are exposed to every day without even realising it. Everyone is at risk of getting cancer during their lifetime.

The mammographer makes sure that:

  • your radiation dose is kept as low as possible
  • the benefits of having the X-ray are greater than any risks

If you have a breast lump or other problem, the risk of not doing the test is much greater than the risk of the radiation dose.

If you are or might be pregnant

Any radiation to the womb is so low that it cannot be measured. For this reason, it is not necessary to wear a shield to cover your tummy (abdomen) during the procedure.

However, it is useful for us to know if you are or might be pregnant. This can affect what imaging is done on the day of your procedure. It is also important for us to know if you are breastfeeding. The X-ray pictures of your breasts are then more complex to interpret.

When you get your appointment, please contact the breast imaging unit straight away if you:

  • are pregnant
  • think that you might be pregnant
  • are currently breastfeeding

We can then decide if another test, such as a breast ultrasound scan, may be more suitable for you.

Preparing for a mammogram

There are no special preparations for having a mammogram. You can eat and drink as usual before and after the procedure. But some things can make your breast screening appointment easier.


  • Contact the breast imaging unit in advance if you need a hoist (piece of medical equipment to help lift or move you safely), transport or a translator.
  • Wear clothes that you can remove easily. This is because we ask you to undress from the waist upwards.
  • Tell us when you arrive for your appointment if you have breast implants.
  • Try to bring a family member or friend with you to your  appointment. This may also be useful if you do not understand English well or have any special needs. Although your family member or friend may not be allowed into the examination room, they can support you and accompany you home.
  • Bring an adult to supervise your children if they need to come with you to your appointment. We do not have childcare facilities.
  • If you wish, tell staff the pronouns (such as he or him, she or her, or they or them) that we should use to address you.


  • Do not wear spray deodorant (roll-on deodorant is OK), powder, lotion or perfume on your breasts and underarm areas on the day of your appointment. These products can affect the X-ray pictures.

Preparing for a mammogram if you are trans or non-binary

There is information about who should have breast screening and the invitation process on the government website.

If you have any questions or concerns about breast screening, you can:

You may want to bring someone with you to your appointment for support.

It is important that you feel treated with respect and dignity at all times. When booking your appointment, please tell us if you would prefer to be seen at the beginning or end of a clinic.

We may ask you to sit in a waiting area when you arrive for your appointment. Please tell our staff if you do not feel comfortable waiting with other people.

There is a cubicle with curtains where you get undressed from the waist upwards before your mammogram. If you wear a binder (a piece of clothing to flatten breast tissue), you will need to remove this before the mammogram.

We want to involve you in decisions about your care and treatment. If you decide to have a mammogram, we will ask you to sign a consent form. This says that you agree to have the test and understand what it involves.

If you would like more information about our consent process, please speak to a member of staff caring for you.

Having the procedure

The procedure should last no longer than 15 minutes.

What happens during the procedure

  1. The mammographer calls you into the X-ray room. They ask you a few questions about your general health and explain the procedure. You can ask the mammographer any more questions that you may have.
  2. If you are happy to have the test, the mammographer will ask you to remove all your clothes from the waist upwards. We have a cubicle with curtains where you get undressed.
  3. The mammographer asks you to stand in front of the X-ray machine. They then get you into position for your mammogram.
  4. The mammographer puts each breast, in turn, onto the X-ray machine. Your breast is pressed firmly between 2 clear plates for a few seconds. This does not harm the breast. The pressure is needed to keep the breast still and get the clearest picture with the lowest amount of radiation possible.
  5. Usually, the mammographer takes 2 pictures of each breast. If your breasts are larger than average, the mammographer may need to take more than 2 pictures of each breast.

How the procedure feels

Some people find it slightly uncomfortable when their breasts are pressed between the 2 plates and some feel temporary pain.

Research has shown that many people think a mammogram is less painful than having a blood test. They find that the pressure or squeezing effect needed to keep the breasts still compares to having blood pressure measured.

After the procedure

You can return to your usual activities, including work and sports, immediately.

After a mammogram, you should not have any side effects that cause concern. However, please contact us if you need any advice.

Getting your breast screening results

Specialist doctors called radiologists or specially trained mammographers review the mammogram pictures. They send a report explaining the results to the doctor who referred you for this test.

Sometimes, we ask you to come for another mammogram. We may need to examine any areas of change in the breast more closely. Although this may seem alarming at the time, it is a common procedure to help us give the most accurate report possible.

You may have come for your mammogram as part of an appointment at the breast unit one stop clinic. If so, we may ask you to return here after all your tests have been done. The breast consultant can then explain your results.

Otherwise, you get your results in the post and we send a copy to your GP. This is usually within 2 weeks.

If you have come for an outpatient mammogram appointment, the breast unit will post you and your GP the results. This may take up to 4 weeks. If we have not contacted you within 4 weeks, please phone the breast unit secretaries on 020 7188 1469.

Resource number: 3323/VER6
Last reviewed: September 2023
Next review due: September 2026

A list of sources is available on request.

Trusted Information Creator. Patient Information Forum

Contact us

Please contact us if you have any questions.


  • For your breast imaging appointment: 020 7188 8317, Monday to Friday, 9am to 5pm
  • For outpatient clinic appointment bookings: 020 7188 0881 or 020 7188 7188, extension 53480, Monday to Friday, 9am to 5pm
  • For your results, contact the breast unit secretaries: 020 7188 1469, Monday to Friday, 9am to 5pm
  • For the breast care nurses: 020 7188 0869, Monday to Friday, 9am to 5pm


Breast imaging unit: [email protected]

We aim to respond to emails within 2 working days.


Breast imaging unit, 3rd floor, Tower Wing, Guy's Hospital, Great Maze Pond, London SE1 9RT

Pharmacy medicines helpline

If you have any questions or concerns about your medicines, please speak to the staff caring for you.

You can also contact our pharmacy medicines helpline.

Phone: 020 7188 8748, Monday to Friday, 9am to 5pm

Email: [email protected]

We aim to respond to emails within 2 working days.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

Is this health information page useful?