Your bones are made of living tissue. To keep them strong, your body breaks down old bone and replaces it with new bone. But when more bone is broken down than replaced, you lose bone density, also called bone mass. Bone density is a measure of the amount of calcium and other minerals in bone. Bones containing more minerals are denser. They tend to be stronger and less likely to fracture (break).

Losing bone density can weaken your bones. In some cases, it can lead to osteoporosis. This is a disease which can make your bones more likely to break. Low bone density that is not low enough to be osteoporosis is sometimes called osteopenia.

Your bones become less dense as you age. Other factors can also make you more likely to lose bone mass, such as:

• A family history of osteoporosis or low bone mass
• Not developing good bone mass when you are young
• Having certain medical conditions, such as:
  • Endocrine diseases
  • Certain digestive diseases
  • Rheumatoid arthritis
  • Certain types of cancer
  • HIV
  • Anorexia nervosa, a type of eating disorder
• Taking certain medicines, such as:
  • Corticosteroids
  • Proton pump inhibitors (which treat GERD)
  • Medicines to treat epilepsy
• Smoking tobacco
• Long-term heavy alcohol use
• Physical inactivity or prolonged periods of bedrest

Not everyone who has low bone mass gets osteoporosis, but they are at higher risk for developing it.

A bone density scan is the best way to measure your bone health. It compares your bone density, or mass, to that of a healthy person who is the same age and sex as you are. It can show:

• Whether you have low bone density
• Whether you have osteoporosis, a disease that makes your bones weak
• Your risk for breaking bones
• Whether your osteoporosis treatment is working

To help keep your bones strong and help prevent osteoporosis, the best thing to do is to eat a healthy diet rich in calcium and vitamin D. Getting regular physical activity, limiting alcohol, and not smoking can also help. In some cases, your health care provider may prescribe medicines to prevent osteoporosis.

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases