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Bone Density Scan
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Bone Density Scan

A bone density scan, or DEXA scan, is a low-dose x-ray used to measure bone mineral density and assess your risk for fractures and osteoporosis.

What is a bone density scan?

A bone density scan, also known as a DEXA or DXA scan, is a low-dose x-ray that measures calcium and other minerals in your bones. Bones containing more minerals are denser and tend to be stronger and less likely to break. This measurement helps show your bone's strength and thickness.

As you age or develop certain medical conditions, bones can become thinner, a condition known as osteopenia. This puts you at risk for osteoporosis, a disease that causes bones to become very thin and brittle, increasing the risk of fractures in the hips, spine, and wrists.

Why do I need a bone density scan?

Most women age 65 or older should have a bone density scan. Other individuals may be at risk if they have a very low body weight, have had one or more fractures after age 50, have lost a half inch or more in height within one year, or have a family history of osteoporosis. Additional risk factors include lack of physical activity, long-term tobacco or alcohol use, inadequate calcium and vitamin D intake, or medical conditions like diabetes or rheumatoid arthritis.

What happens during a bone density scan?

The most common method is a central DEXA scan, which checks the bone density of your lower spine, hip, wrist, or entire body. You will lie on a padded table while the scanning machine passes over you. You must stay very still during the 10 to 30-minute procedure. A peripheral DEXA (p-DEXA) scan may be used to check your finger, hand, forearm, or foot; while faster, it provides less detail than a central scan.

What do the results mean?

Results are given as T-scores (comparing your density to a healthy young adult) and Z-scores (comparing your density to others of your age, weight, and sex). T-score results indicate:

  • -1.0 or higher: Normal bone density.
  • -1.0 to -2.4: Low bone density (osteopenia).
  • -2.5 or less: Osteoporosis.

If you have low bone density, your provider may recommend increased exercise, dietary changes (calcium and vitamin D), or prescription medications.

Frequently Asked Questions

The frequency depends on your initial results and risk factors. If your first scan is normal (T‑score above –1.0) and you have no additional risk factors, doctors often recommend repeating it every 5–10 years. If you have osteopenia (T‑score between –1.0 and –2.5) or risk factors such as a family history of fractures, low body weight, or use of steroids, a repeat scan every 2–3 years is common. Your provider will tailor the interval based on your individual risk profile and any changes in your health status.
The T‑score compares your bone density to the average peak density of a healthy 30‑year‑old of the same sex; a T‑score of –2.5 or lower indicates osteoporosis. The Z‑score compares your density to people of the same age, sex, and ethnicity; a Z‑score below –2.0 may suggest secondary causes of bone loss. A low T‑score typically prompts treatment with calcium, vitamin D, and possibly bisphosphonates or other osteoporosis medications. A low Z‑score may lead your clinician to investigate underlying conditions such as endocrine disorders or chronic steroid use.
Taking calcium or vitamin D supplements right before the scan does not affect the results; the test measures bone mineral density, not serum levels. However, you should avoid taking high‑dose calcium supplements on the day of the scan because they can temporarily increase calcium in the blood and may interfere with other lab tests if ordered concurrently. Regular weight‑bearing exercise (walking, jogging, resistance training) is beneficial for bone health, but it should be part of your routine rather than a last‑minute preparation.
Focus on a balanced diet rich in calcium (1,200 mg/day for adults over 50) and vitamin D (800–1,000 IU/day). Engage in regular weight‑bearing and muscle‑strengthening exercises at least 3 times per week. Avoid smoking and limit alcohol to no more than one drink per day for women and two for men. Discuss with your provider whether a calcium or vitamin D supplement is needed, and consider a fall‑prevention plan that includes home safety checks and balance training.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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