Bone Density Scan (DEXA): Preparation and Results

A bone density scan, also known as a DEXA (dual-energy X-ray absorptiometry) scan, is a test that measures how strong and dense your bones are. Bone density refers to how much calcium and other minerals are packed into a section of bone. The more dense the bone, the stronger it usually is.

The DEXA scan uses a very low dose of X-rays to measure bone density. It most often looks at bones that are more likely to break, such as:

• the hip
• the spine
• sometimes the forearm

The test is painless and non-invasive. You do not need injections, needles, or dye. Because the radiation level is very low, the test is considered safe for most people.

Doctors use DEXA scans to:

• Diagnose osteoporosis or osteopenia
• Estimate fracture risk
• Monitor bone changes over time

Check how well bone treatments are working.

Why is a bone density scan ordered?

A bone density scan is ordered to evaluate bone health and identify bone loss early. Osteoporosis often has no symptoms until you have a fracture, so screening is important.

Your provider may recommend a DEXA scan if you:

• Are a woman age 65 or older
• Are a man age 70 or older
• Are post-menopause and have risk factors for bone loss
• Have had a fracture from a minor fall or injury
• Have a family history of osteoporosis
• Have low body weight or poor nutrition
• Smoke or drink alcohol heavily
• Take certain medicine that weaken bones

Medicine that may affect bone health

Some medicines can reduce bone density over time, including:

• long-term steroid use (such as prednisone)
• certain cancer treatments
• some seizure medicine
• thyroid hormone in high doses

Other Medical Conditions

A DEXA scan may also be ordered if you have conditions that affect bone health, such as:

• Rheumatoid arthritis
• Thyroid disorders
• Digestive diseases that limit nutrient absorption
• Chronic kidney disease

The scan helps doctors decide whether you need treatment, lifestyle changes, or further testing.

A DEXA scan and a bone scan sound similar, but they are very different tests used for different reasons.

Bone Density Scan (DEXA)

• Measures bone strength and thickness
• Uses very low-dose X-rays
• Focuses on fracture risk and osteoporosis
• Does not require injections
• Takes about 10–20 minutes

Bone Scan

• Shows bone activity and damage
• Uses a tracer injected into a vein
• Helps detect infections, cancer, fractures, or swelling
• Takes several hours to complete
• Shows “hot spots” where bone activity is abnormal

In simple terms:

• A DEXA scan tells how strong your bones are
• A bone scan shows if something unusual is happening inside the bones

Your doctor will choose the test based on your symptoms and medical needs.

How often do I need a bone density scan?

How often you need a bone density scan depends on your age, risk factors, and previous results.

General Guidelines

• Most adults with normal bone density need a scan every 5–10 years
• People with osteopenia may need testing every 2–5 years
• People with osteoporosis or on treatment may need scans every 1–2 years

Factors That Affect Testing Frequency

Your provider may recommend more frequent scans if you:

• Have rapid bone loss
• Are starting or changing osteoporosis treatment
• Have had a fracture
• Take medicine that affect bone density

The goal is to balance monitoring bone health with avoiding unnecessary testing.

Preparing for a DEXA scan is simple and usually requires very little effort.

Before the Test

• You can eat and drink normally
• Take your usual medicine unless told otherwise
• Do not take calcium supplements for 24 hours before the test
• Wear comfortable clothing without metal zippers, buttons, or belts

What to Avoid

• Avoid wearing jewelry or metal objects
• Tell your provider if you recently had a CT scan or contrast study
• Inform the technician if you might be pregnant

There is no need to fast or change your daily routine.

What happens during a bone density scan?

A DEXA scan is quick, painless, and easy for most people.

Step-by-Step

1. Arrival

• You may be asked to change into a gown
• You remove metal objects that could interfere with imaging

2. Positioning

• You lie flat on a padded table
• A foam block may be placed under your legs to support your spine

3. Scanning

• A scanning arm moves slowly over your body
• The machine takes images of your bones
• You must stay still, but you can breathe normally

4. Completion

• The scan takes about 10 to 20 minutes
• You can leave right away and resume normal activities

You will not feel the X-rays, and there is no recovery time needed.

DEXA scan results are reported as scores that compare your bone density to reference values.

T-Score

The T-score compares your bone density to that of a healthy young adult.

• Normal: –1.0 or higher
• Osteopenia (low bone mass): between –1.0 and –2.5
• Osteoporosis: –2.5 or lower

The lower the T-score, the weaker the bones and the higher the fracture risk.

Z-Score

The Z-score compares your bone density to people of your same age, sex, and body size.

• A low Z-score may suggest an underlying condition

Z-scores are more often used in younger adults and children.

What do the results mean?

Your provider will review your scores along with:

• Age
• Gender
• Medical history
• Fracture history
• Risk factors

Results help guide decisions about:

• Lifestyle changes
• Calcium and vitamin D intake
• Exercise programs
• Medicine to strengthen bones.

Normal Results

Normal bone density means your bones are strong for your age. Your provider may recommend healthy habits and routine follow-up testing.

Abnormal Results

Low bone density does not always mean you will have a fracture. Many people with osteopenia never develop osteoporosis. Early detection allows you to take steps to protect your bones.

A bone density scan is a useful tool for protecting long-term bone health. It is safe, fast, and provides information about fracture risk. Because bone loss often happens without symptoms, a DEXA scan can detect problems early.

If you are recommended a bone density scan, knowing what to expect can help you feel prepared. Ask questions about your results and what steps you can take to keep your bones strong and healthy.