Bone Mineral Density (BMD) factsheet

Introduction

A BMD test measures the amount of mineral in your bones.

The results help doctors diagnose osteoporosis – a disease that makes bones become weak and brittle, increasing the risk of fractures.

Osteoporosis happens when bones lose minerals, such as calcium, more quickly than they replace minerals. In children and adolescents, osteoporosis can also occur if the amount of mineral in the bone does not increase at the normal rate.  

This factsheet is for educational purposes only. For further information regarding this topic, please the medical team at your treating hospital.

 Before the test

Pregancy

Before undergoing a BMD test, it's important to inform your doctor and the imaging staff if you are pregnant or suspect you might be pregnant.

It is recommended that individuals who are pregnant delay their BMD test until after the child is born.

Plaster casts

Plaster casts and any medical imaging that uses a contrasting agent (e.g. Nuclear Medicine, Barium X-ray, CT or MRI) impact on BMD measurements. 

If you have a plaster cast, or other medical imaging procedures planned, please tell the booking clerk when making an appointment so an appropriate timeframe is allowed.

Suitable clothing

No special preparation is required; however, you will need to remove any shell, metallic, silicon or thick objects that may be on you or your clothes.

If you wear light cotton clothing without metal, and no jewelry, then you should only need to remove your shoes for the procedure. 

 During the test (about 30 min)

Medical history check

A brief medical history, including height, weight, previous fractures, and current medications will be recorded.

DXA machine takes bone measurements

BMD is usually measured by a dual-energy x-ray absorptiometry (DXA) machine. A DXA machine looks like a bed with a narrow “scan arm” above it. 

It uses a very weak x-ray to measure your bones. There are no needles, it is not noisy, and it does not hurt.

During the test, you lie on the DXA machine, and its scan arm slowly moves over you, taking pictures of your whole body, spine, and hip.

 After the test

You can return to your normal activities immediately after your test. 

A nuclear medicine physician (a specialist doctor) will interpret the results. The results will be sent to your referring doctor who will discuss them with you. 

Radiation

During this test you will be exposed to a very small amount of radiation.

The benefits of finding an injury or disease are generally much more important than the potential risk from receiving a small dose of radiation. 

Your treating doctor will discuss the potential risks with you. 

Last updated Tuesday 18th June 2024

Disclaimer

This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024


This factsheet was produced with support from John Hunter Children's Hospital.